Initial vendor packages

Signed-off-by: Valentin Popov <valentin@popov.link>

1 files changed, 1483 insertions, 0 deletions

diff --git a/vendor/image/src/codecs/bmp/decoder.rs b/vendor/image/src/codecs/bmp/decoder.rs
new file mode 100644
index 0000000..58c0650
--- /dev/null
+++ b/vendor/image/src/codecs/bmp/decoder.rs
@@ -0,0 +1,1483 @@
+use std::cmp::{self, Ordering};
+use std::convert::TryFrom;
+use std::io::{self, Cursor, Read, Seek, SeekFrom};
+use std::iter::{repeat, Iterator, Rev};
+use std::marker::PhantomData;
+use std::slice::ChunksMut;
+use std::{error, fmt, mem};
+
+use byteorder::{LittleEndian, ReadBytesExt};
+
+use crate::color::ColorType;
+use crate::error::{
+    DecodingError, ImageError, ImageResult, UnsupportedError, UnsupportedErrorKind,
+};
+use crate::image::{self, ImageDecoder, ImageDecoderRect, ImageFormat, Progress};
+
+const BITMAPCOREHEADER_SIZE: u32 = 12;
+const BITMAPINFOHEADER_SIZE: u32 = 40;
+const BITMAPV2HEADER_SIZE: u32 = 52;
+const BITMAPV3HEADER_SIZE: u32 = 56;
+const BITMAPV4HEADER_SIZE: u32 = 108;
+const BITMAPV5HEADER_SIZE: u32 = 124;
+
+static LOOKUP_TABLE_3_BIT_TO_8_BIT: [u8; 8] = [0, 36, 73, 109, 146, 182, 219, 255];
+static LOOKUP_TABLE_4_BIT_TO_8_BIT: [u8; 16] = [
+    0, 17, 34, 51, 68, 85, 102, 119, 136, 153, 170, 187, 204, 221, 238, 255,
+];
+static LOOKUP_TABLE_5_BIT_TO_8_BIT: [u8; 32] = [
+    0, 8, 16, 25, 33, 41, 49, 58, 66, 74, 82, 90, 99, 107, 115, 123, 132, 140, 148, 156, 165, 173,
+    181, 189, 197, 206, 214, 222, 230, 239, 247, 255,
+];
+static LOOKUP_TABLE_6_BIT_TO_8_BIT: [u8; 64] = [
+    0, 4, 8, 12, 16, 20, 24, 28, 32, 36, 40, 45, 49, 53, 57, 61, 65, 69, 73, 77, 81, 85, 89, 93,
+    97, 101, 105, 109, 113, 117, 121, 125, 130, 134, 138, 142, 146, 150, 154, 158, 162, 166, 170,
+    174, 178, 182, 186, 190, 194, 198, 202, 206, 210, 215, 219, 223, 227, 231, 235, 239, 243, 247,
+    251, 255,
+];
+
+static R5_G5_B5_COLOR_MASK: Bitfields = Bitfields {
+    r: Bitfield { len: 5, shift: 10 },
+    g: Bitfield { len: 5, shift: 5 },
+    b: Bitfield { len: 5, shift: 0 },
+    a: Bitfield { len: 0, shift: 0 },
+};
+const R8_G8_B8_COLOR_MASK: Bitfields = Bitfields {
+    r: Bitfield { len: 8, shift: 24 },
+    g: Bitfield { len: 8, shift: 16 },
+    b: Bitfield { len: 8, shift: 8 },
+    a: Bitfield { len: 0, shift: 0 },
+};
+const R8_G8_B8_A8_COLOR_MASK: Bitfields = Bitfields {
+    r: Bitfield { len: 8, shift: 16 },
+    g: Bitfield { len: 8, shift: 8 },
+    b: Bitfield { len: 8, shift: 0 },
+    a: Bitfield { len: 8, shift: 24 },
+};
+
+const RLE_ESCAPE: u8 = 0;
+const RLE_ESCAPE_EOL: u8 = 0;
+const RLE_ESCAPE_EOF: u8 = 1;
+const RLE_ESCAPE_DELTA: u8 = 2;
+
+/// The maximum width/height the decoder will process.
+const MAX_WIDTH_HEIGHT: i32 = 0xFFFF;
+
+#[derive(PartialEq, Copy, Clone)]
+enum ImageType {
+    Palette,
+    RGB16,
+    RGB24,
+    RGB32,
+    RGBA32,
+    RLE8,
+    RLE4,
+    Bitfields16,
+    Bitfields32,
+}
+
+#[derive(PartialEq)]
+enum BMPHeaderType {
+    Core,
+    Info,
+    V2,
+    V3,
+    V4,
+    V5,
+}
+
+#[derive(PartialEq)]
+enum FormatFullBytes {
+    RGB24,
+    RGB32,
+    RGBA32,
+    Format888,
+}
+
+enum Chunker<'a> {
+    FromTop(ChunksMut<'a, u8>),
+    FromBottom(Rev<ChunksMut<'a, u8>>),
+}
+
+pub(crate) struct RowIterator<'a> {
+    chunks: Chunker<'a>,
+}
+
+impl<'a> Iterator for RowIterator<'a> {
+    type Item = &'a mut [u8];
+
+    #[inline(always)]
+    fn next(&mut self) -> Option<&'a mut [u8]> {
+        match self.chunks {
+            Chunker::FromTop(ref mut chunks) => chunks.next(),
+            Chunker::FromBottom(ref mut chunks) => chunks.next(),
+        }
+    }
+}
+
+/// All errors that can occur when attempting to parse a BMP
+#[derive(Debug, Copy, Clone, Hash, PartialEq, Eq, PartialOrd, Ord)]
+enum DecoderError {
+    // Failed to decompress RLE data.
+    CorruptRleData,
+
+    /// The bitfield mask interleaves set and unset bits
+    BitfieldMaskNonContiguous,
+    /// Bitfield mask invalid (e.g. too long for specified type)
+    BitfieldMaskInvalid,
+    /// Bitfield (of the specified width – 16- or 32-bit) mask not present
+    BitfieldMaskMissing(u32),
+    /// Bitfield (of the specified width – 16- or 32-bit) masks not present
+    BitfieldMasksMissing(u32),
+
+    /// BMP's "BM" signature wrong or missing
+    BmpSignatureInvalid,
+    /// More than the exactly one allowed plane specified by the format
+    MoreThanOnePlane,
+    /// Invalid amount of bits per channel for the specified image type
+    InvalidChannelWidth(ChannelWidthError, u16),
+
+    /// The width is negative
+    NegativeWidth(i32),
+    /// One of the dimensions is larger than a soft limit
+    ImageTooLarge(i32, i32),
+    /// The height is `i32::min_value()`
+    ///
+    /// General negative heights specify top-down DIBs
+    InvalidHeight,
+
+    /// Specified image type is invalid for top-down BMPs (i.e. is compressed)
+    ImageTypeInvalidForTopDown(u32),
+    /// Image type not currently recognized by the decoder
+    ImageTypeUnknown(u32),
+
+    /// Bitmap header smaller than the core header
+    HeaderTooSmall(u32),
+
+    /// The palette is bigger than allowed by the bit count of the BMP
+    PaletteSizeExceeded {
+        colors_used: u32,
+        bit_count: u16,
+    },
+}
+
+impl fmt::Display for DecoderError {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        match self {
+            DecoderError::CorruptRleData => f.write_str("Corrupt RLE data"),
+            DecoderError::BitfieldMaskNonContiguous => f.write_str("Non-contiguous bitfield mask"),
+            DecoderError::BitfieldMaskInvalid => f.write_str("Invalid bitfield mask"),
+            DecoderError::BitfieldMaskMissing(bb) => {
+                f.write_fmt(format_args!("Missing {}-bit bitfield mask", bb))
+            }
+            DecoderError::BitfieldMasksMissing(bb) => {
+                f.write_fmt(format_args!("Missing {}-bit bitfield masks", bb))
+            }
+            DecoderError::BmpSignatureInvalid => f.write_str("BMP signature not found"),
+            DecoderError::MoreThanOnePlane => f.write_str("More than one plane"),
+            DecoderError::InvalidChannelWidth(tp, n) => {
+                f.write_fmt(format_args!("Invalid channel bit count for {}: {}", tp, n))
+            }
+            DecoderError::NegativeWidth(w) => f.write_fmt(format_args!("Negative width ({})", w)),
+            DecoderError::ImageTooLarge(w, h) => f.write_fmt(format_args!(
+                "Image too large (one of ({}, {}) > soft limit of {})",
+                w, h, MAX_WIDTH_HEIGHT
+            )),
+            DecoderError::InvalidHeight => f.write_str("Invalid height"),
+            DecoderError::ImageTypeInvalidForTopDown(tp) => f.write_fmt(format_args!(
+                "Invalid image type {} for top-down image.",
+                tp
+            )),
+            DecoderError::ImageTypeUnknown(tp) => {
+                f.write_fmt(format_args!("Unknown image compression type {}", tp))
+            }
+            DecoderError::HeaderTooSmall(s) => {
+                f.write_fmt(format_args!("Bitmap header too small ({} bytes)", s))
+            }
+            DecoderError::PaletteSizeExceeded {
+                colors_used,
+                bit_count,
+            } => f.write_fmt(format_args!(
+                "Palette size {} exceeds maximum size for BMP with bit count of {}",
+                colors_used, bit_count
+            )),
+        }
+    }
+}
+
+impl From<DecoderError> for ImageError {
+    fn from(e: DecoderError) -> ImageError {
+        ImageError::Decoding(DecodingError::new(ImageFormat::Bmp.into(), e))
+    }
+}
+
+impl error::Error for DecoderError {}
+
+/// Distinct image types whose saved channel width can be invalid
+#[derive(Debug, Copy, Clone, Hash, PartialEq, Eq, PartialOrd, Ord)]
+enum ChannelWidthError {
+    /// RGB
+    Rgb,
+    /// 8-bit run length encoding
+    Rle8,
+    /// 4-bit run length encoding
+    Rle4,
+    /// Bitfields (16- or 32-bit)
+    Bitfields,
+}
+
+impl fmt::Display for ChannelWidthError {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        f.write_str(match self {
+            ChannelWidthError::Rgb => "RGB",
+            ChannelWidthError::Rle8 => "RLE8",
+            ChannelWidthError::Rle4 => "RLE4",
+            ChannelWidthError::Bitfields => "bitfields",
+        })
+    }
+}
+
+/// Convenience function to check if the combination of width, length and number of
+/// channels would result in a buffer that would overflow.
+fn check_for_overflow(width: i32, length: i32, channels: usize) -> ImageResult<()> {
+    num_bytes(width, length, channels)
+        .map(|_| ())
+        .ok_or_else(|| {
+            ImageError::Unsupported(UnsupportedError::from_format_and_kind(
+                ImageFormat::Bmp.into(),
+                UnsupportedErrorKind::GenericFeature(format!(
+                    "Image dimensions ({}x{} w/{} channels) are too large",
+                    width, length, channels
+                )),
+            ))
+        })
+}
+
+/// Calculate how many many bytes a buffer holding a decoded image with these properties would
+/// require. Returns `None` if the buffer size would overflow or if one of the sizes are negative.
+fn num_bytes(width: i32, length: i32, channels: usize) -> Option<usize> {
+    if width <= 0 || length <= 0 {
+        None
+    } else {
+        match channels.checked_mul(width as usize) {
+            Some(n) => n.checked_mul(length as usize),
+            None => None,
+        }
+    }
+}
+
+/// Call the provided function on each row of the provided buffer, returning Err if the provided
+/// function returns an error, extends the buffer if it's not large enough.
+fn with_rows<F>(
+    buffer: &mut [u8],
+    width: i32,
+    height: i32,
+    channels: usize,
+    top_down: bool,
+    mut func: F,
+) -> io::Result<()>
+where
+    F: FnMut(&mut [u8]) -> io::Result<()>,
+{
+    // An overflow should already have been checked for when this is called,
+    // though we check anyhow, as it somehow seems to increase performance slightly.
+    let row_width = channels.checked_mul(width as usize).unwrap();
+    let full_image_size = row_width.checked_mul(height as usize).unwrap();
+    assert_eq!(buffer.len(), full_image_size);
+
+    if !top_down {
+        for row in buffer.chunks_mut(row_width).rev() {
+            func(row)?;
+        }
+    } else {
+        for row in buffer.chunks_mut(row_width) {
+            func(row)?;
+        }
+    }
+    Ok(())
+}
+
+fn set_8bit_pixel_run<'a, T: Iterator<Item = &'a u8>>(
+    pixel_iter: &mut ChunksMut<u8>,
+    palette: &[[u8; 3]],
+    indices: T,
+    n_pixels: usize,
+) -> bool {
+    for idx in indices.take(n_pixels) {
+        if let Some(pixel) = pixel_iter.next() {
+            let rgb = palette[*idx as usize];
+            pixel[0] = rgb[0];
+            pixel[1] = rgb[1];
+            pixel[2] = rgb[2];
+        } else {
+            return false;
+        }
+    }
+    true
+}
+
+fn set_4bit_pixel_run<'a, T: Iterator<Item = &'a u8>>(
+    pixel_iter: &mut ChunksMut<u8>,
+    palette: &[[u8; 3]],
+    indices: T,
+    mut n_pixels: usize,
+) -> bool {
+    for idx in indices {
+        macro_rules! set_pixel {
+            ($i:expr) => {
+                if n_pixels == 0 {
+                    break;
+                }
+                if let Some(pixel) = pixel_iter.next() {
+                    let rgb = palette[$i as usize];
+                    pixel[0] = rgb[0];
+                    pixel[1] = rgb[1];
+                    pixel[2] = rgb[2];
+                } else {
+                    return false;
+                }
+                n_pixels -= 1;
+            };
+        }
+        set_pixel!(idx >> 4);
+        set_pixel!(idx & 0xf);
+    }
+    true
+}
+
+#[rustfmt::skip]
+fn set_2bit_pixel_run<'a, T: Iterator<Item = &'a u8>>(
+    pixel_iter: &mut ChunksMut<u8>,
+    palette: &[[u8; 3]],
+    indices: T,
+    mut n_pixels: usize,
+) -> bool {
+    for idx in indices {
+        macro_rules! set_pixel {
+            ($i:expr) => {
+                if n_pixels == 0 {
+                    break;
+                }
+                if let Some(pixel) = pixel_iter.next() {
+                    let rgb = palette[$i as usize];
+                    pixel[0] = rgb[0];
+                    pixel[1] = rgb[1];
+                    pixel[2] = rgb[2];
+                } else {
+                    return false;
+                }
+                n_pixels -= 1;
+            };
+        }
+        set_pixel!((idx >> 6) & 0x3u8);
+        set_pixel!((idx >> 4) & 0x3u8);
+        set_pixel!((idx >> 2) & 0x3u8);
+        set_pixel!( idx       & 0x3u8);
+    }
+    true
+}
+
+fn set_1bit_pixel_run<'a, T: Iterator<Item = &'a u8>>(
+    pixel_iter: &mut ChunksMut<u8>,
+    palette: &[[u8; 3]],
+    indices: T,
+) {
+    for idx in indices {
+        let mut bit = 0x80;
+        loop {
+            if let Some(pixel) = pixel_iter.next() {
+                let rgb = palette[((idx & bit) != 0) as usize];
+                pixel[0] = rgb[0];
+                pixel[1] = rgb[1];
+                pixel[2] = rgb[2];
+            } else {
+                return;
+            }
+
+            bit >>= 1;
+            if bit == 0 {
+                break;
+            }
+        }
+    }
+}
+
+#[derive(PartialEq, Eq)]
+struct Bitfield {
+    shift: u32,
+    len: u32,
+}
+
+impl Bitfield {
+    fn from_mask(mask: u32, max_len: u32) -> ImageResult<Bitfield> {
+        if mask == 0 {
+            return Ok(Bitfield { shift: 0, len: 0 });
+        }
+        let mut shift = mask.trailing_zeros();
+        let mut len = (!(mask >> shift)).trailing_zeros();
+        if len != mask.count_ones() {
+            return Err(DecoderError::BitfieldMaskNonContiguous.into());
+        }
+        if len + shift > max_len {
+            return Err(DecoderError::BitfieldMaskInvalid.into());
+        }
+        if len > 8 {
+            shift += len - 8;
+            len = 8;
+        }
+        Ok(Bitfield { shift, len })
+    }
+
+    fn read(&self, data: u32) -> u8 {
+        let data = data >> self.shift;
+        match self.len {
+            1 => ((data & 0b1) * 0xff) as u8,
+            2 => ((data & 0b11) * 0x55) as u8,
+            3 => LOOKUP_TABLE_3_BIT_TO_8_BIT[(data & 0b00_0111) as usize],
+            4 => LOOKUP_TABLE_4_BIT_TO_8_BIT[(data & 0b00_1111) as usize],
+            5 => LOOKUP_TABLE_5_BIT_TO_8_BIT[(data & 0b01_1111) as usize],
+            6 => LOOKUP_TABLE_6_BIT_TO_8_BIT[(data & 0b11_1111) as usize],
+            7 => ((data & 0x7f) << 1 | (data & 0x7f) >> 6) as u8,
+            8 => (data & 0xff) as u8,
+            _ => panic!(),
+        }
+    }
+}
+
+#[derive(PartialEq, Eq)]
+struct Bitfields {
+    r: Bitfield,
+    g: Bitfield,
+    b: Bitfield,
+    a: Bitfield,
+}
+
+impl Bitfields {
+    fn from_mask(
+        r_mask: u32,
+        g_mask: u32,
+        b_mask: u32,
+        a_mask: u32,
+        max_len: u32,
+    ) -> ImageResult<Bitfields> {
+        let bitfields = Bitfields {
+            r: Bitfield::from_mask(r_mask, max_len)?,
+            g: Bitfield::from_mask(g_mask, max_len)?,
+            b: Bitfield::from_mask(b_mask, max_len)?,
+            a: Bitfield::from_mask(a_mask, max_len)?,
+        };
+        if bitfields.r.len == 0 || bitfields.g.len == 0 || bitfields.b.len == 0 {
+            return Err(DecoderError::BitfieldMaskMissing(max_len).into());
+        }
+        Ok(bitfields)
+    }
+}
+
+/// A bmp decoder
+pub struct BmpDecoder<R> {
+    reader: R,
+
+    bmp_header_type: BMPHeaderType,
+    indexed_color: bool,
+
+    width: i32,
+    height: i32,
+    data_offset: u64,
+    top_down: bool,
+    no_file_header: bool,
+    add_alpha_channel: bool,
+    has_loaded_metadata: bool,
+    image_type: ImageType,
+
+    bit_count: u16,
+    colors_used: u32,
+    palette: Option<Vec<[u8; 3]>>,
+    bitfields: Option<Bitfields>,
+}
+
+enum RLEInsn {
+    EndOfFile,
+    EndOfRow,
+    Delta(u8, u8),
+    Absolute(u8, Vec<u8>),
+    PixelRun(u8, u8),
+}
+
+impl<R: Read + Seek> BmpDecoder<R> {
+    fn new_decoder(reader: R) -> BmpDecoder<R> {
+        BmpDecoder {
+            reader,
+
+            bmp_header_type: BMPHeaderType::Info,
+            indexed_color: false,
+
+            width: 0,
+            height: 0,
+            data_offset: 0,
+            top_down: false,
+            no_file_header: false,
+            add_alpha_channel: false,
+            has_loaded_metadata: false,
+            image_type: ImageType::Palette,
+
+            bit_count: 0,
+            colors_used: 0,
+            palette: None,
+            bitfields: None,
+        }
+    }
+
+    /// Create a new decoder that decodes from the stream ```r```
+    pub fn new(reader: R) -> ImageResult<BmpDecoder<R>> {
+        let mut decoder = Self::new_decoder(reader);
+        decoder.read_metadata()?;
+        Ok(decoder)
+    }
+
+    /// Create a new decoder that decodes from the stream ```r``` without first
+    /// reading a BITMAPFILEHEADER. This is useful for decoding the CF_DIB format
+    /// directly from the Windows clipboard.
+    pub fn new_without_file_header(reader: R) -> ImageResult<BmpDecoder<R>> {
+        let mut decoder = Self::new_decoder(reader);
+        decoder.no_file_header = true;
+        decoder.read_metadata()?;
+        Ok(decoder)
+    }
+
+    #[cfg(feature = "ico")]
+    pub(crate) fn new_with_ico_format(reader: R) -> ImageResult<BmpDecoder<R>> {
+        let mut decoder = Self::new_decoder(reader);
+        decoder.read_metadata_in_ico_format()?;
+        Ok(decoder)
+    }
+
+    /// If true, the palette in BMP does not apply to the image even if it is found.
+    /// In other words, the output image is the indexed color.
+    pub fn set_indexed_color(&mut self, indexed_color: bool) {
+        self.indexed_color = indexed_color;
+    }
+
+    #[cfg(feature = "ico")]
+    pub(crate) fn reader(&mut self) -> &mut R {
+        &mut self.reader
+    }
+
+    fn read_file_header(&mut self) -> ImageResult<()> {
+        if self.no_file_header {
+            return Ok(());
+        }
+        let mut signature = [0; 2];
+        self.reader.read_exact(&mut signature)?;
+
+        if signature != b"BM"[..] {
+            return Err(DecoderError::BmpSignatureInvalid.into());
+        }
+
+        // The next 8 bytes represent file size, followed the 4 reserved bytes
+        // We're not interesting these values
+        self.reader.read_u32::<LittleEndian>()?;
+        self.reader.read_u32::<LittleEndian>()?;
+
+        self.data_offset = u64::from(self.reader.read_u32::<LittleEndian>()?);
+
+        Ok(())
+    }
+
+    /// Read BITMAPCOREHEADER https://msdn.microsoft.com/en-us/library/vs/alm/dd183372(v=vs.85).aspx
+    ///
+    /// returns Err if any of the values are invalid.
+    fn read_bitmap_core_header(&mut self) -> ImageResult<()> {
+        // As height/width values in BMP files with core headers are only 16 bits long,
+        // they won't be larger than `MAX_WIDTH_HEIGHT`.
+        self.width = i32::from(self.reader.read_u16::<LittleEndian>()?);
+        self.height = i32::from(self.reader.read_u16::<LittleEndian>()?);
+
+        check_for_overflow(self.width, self.height, self.num_channels())?;
+
+        // Number of planes (format specifies that this should be 1).
+        if self.reader.read_u16::<LittleEndian>()? != 1 {
+            return Err(DecoderError::MoreThanOnePlane.into());
+        }
+
+        self.bit_count = self.reader.read_u16::<LittleEndian>()?;
+        self.image_type = match self.bit_count {
+            1 | 4 | 8 => ImageType::Palette,
+            24 => ImageType::RGB24,
+            _ => {
+                return Err(DecoderError::InvalidChannelWidth(
+                    ChannelWidthError::Rgb,
+                    self.bit_count,
+                )
+                .into())
+            }
+        };
+
+        Ok(())
+    }
+
+    /// Read BITMAPINFOHEADER https://msdn.microsoft.com/en-us/library/vs/alm/dd183376(v=vs.85).aspx
+    /// or BITMAPV{2|3|4|5}HEADER.
+    ///
+    /// returns Err if any of the values are invalid.
+    fn read_bitmap_info_header(&mut self) -> ImageResult<()> {
+        self.width = self.reader.read_i32::<LittleEndian>()?;
+        self.height = self.reader.read_i32::<LittleEndian>()?;
+
+        // Width can not be negative
+        if self.width < 0 {
+            return Err(DecoderError::NegativeWidth(self.width).into());
+        } else if self.width > MAX_WIDTH_HEIGHT || self.height > MAX_WIDTH_HEIGHT {
+            // Limit very large image sizes to avoid OOM issues. Images with these sizes are
+            // unlikely to be valid anyhow.
+            return Err(DecoderError::ImageTooLarge(self.width, self.height).into());
+        }
+
+        if self.height == i32::min_value() {
+            return Err(DecoderError::InvalidHeight.into());
+        }
+
+        // A negative height indicates a top-down DIB.
+        if self.height < 0 {
+            self.height *= -1;
+            self.top_down = true;
+        }
+
+        check_for_overflow(self.width, self.height, self.num_channels())?;
+
+        // Number of planes (format specifies that this should be 1).
+        if self.reader.read_u16::<LittleEndian>()? != 1 {
+            return Err(DecoderError::MoreThanOnePlane.into());
+        }
+
+        self.bit_count = self.reader.read_u16::<LittleEndian>()?;
+        let image_type_u32 = self.reader.read_u32::<LittleEndian>()?;
+
+        // Top-down dibs can not be compressed.
+        if self.top_down && image_type_u32 != 0 && image_type_u32 != 3 {
+            return Err(DecoderError::ImageTypeInvalidForTopDown(image_type_u32).into());
+        }
+        self.image_type = match image_type_u32 {
+            0 => match self.bit_count {
+                1 | 2 | 4 | 8 => ImageType::Palette,
+                16 => ImageType::RGB16,
+                24 => ImageType::RGB24,
+                32 if self.add_alpha_channel => ImageType::RGBA32,
+                32 => ImageType::RGB32,
+                _ => {
+                    return Err(DecoderError::InvalidChannelWidth(
+                        ChannelWidthError::Rgb,
+                        self.bit_count,
+                    )
+                    .into())
+                }
+            },
+            1 => match self.bit_count {
+                8 => ImageType::RLE8,
+                _ => {
+                    return Err(DecoderError::InvalidChannelWidth(
+                        ChannelWidthError::Rle8,
+                        self.bit_count,
+                    )
+                    .into())
+                }
+            },
+            2 => match self.bit_count {
+                4 => ImageType::RLE4,
+                _ => {
+                    return Err(DecoderError::InvalidChannelWidth(
+                        ChannelWidthError::Rle4,
+                        self.bit_count,
+                    )
+                    .into())
+                }
+            },
+            3 => match self.bit_count {
+                16 => ImageType::Bitfields16,
+                32 => ImageType::Bitfields32,
+                _ => {
+                    return Err(DecoderError::InvalidChannelWidth(
+                        ChannelWidthError::Bitfields,
+                        self.bit_count,
+                    )
+                    .into())
+                }
+            },
+            4 => {
+                // JPEG compression is not implemented yet.
+                return Err(ImageError::Unsupported(
+                    UnsupportedError::from_format_and_kind(
+                        ImageFormat::Bmp.into(),
+                        UnsupportedErrorKind::GenericFeature("JPEG compression".to_owned()),
+                    ),
+                ));
+            }
+            5 => {
+                // PNG compression is not implemented yet.
+                return Err(ImageError::Unsupported(
+                    UnsupportedError::from_format_and_kind(
+                        ImageFormat::Bmp.into(),
+                        UnsupportedErrorKind::GenericFeature("PNG compression".to_owned()),
+                    ),
+                ));
+            }
+            11 | 12 | 13 => {
+                // CMYK types are not implemented yet.
+                return Err(ImageError::Unsupported(
+                    UnsupportedError::from_format_and_kind(
+                        ImageFormat::Bmp.into(),
+                        UnsupportedErrorKind::GenericFeature("CMYK format".to_owned()),
+                    ),
+                ));
+            }
+            _ => {
+                // Unknown compression type.
+                return Err(DecoderError::ImageTypeUnknown(image_type_u32).into());
+            }
+        };
+
+        // The next 12 bytes represent data array size in bytes,
+        // followed the horizontal and vertical printing resolutions
+        // We will calculate the pixel array size using width & height of image
+        // We're not interesting the horz or vert printing resolutions
+        self.reader.read_u32::<LittleEndian>()?;
+        self.reader.read_u32::<LittleEndian>()?;
+        self.reader.read_u32::<LittleEndian>()?;
+
+        self.colors_used = self.reader.read_u32::<LittleEndian>()?;
+
+        // The next 4 bytes represent number of "important" colors
+        // We're not interested in this value, so we'll skip it
+        self.reader.read_u32::<LittleEndian>()?;
+
+        Ok(())
+    }
+
+    fn read_bitmasks(&mut self) -> ImageResult<()> {
+        let r_mask = self.reader.read_u32::<LittleEndian>()?;
+        let g_mask = self.reader.read_u32::<LittleEndian>()?;
+        let b_mask = self.reader.read_u32::<LittleEndian>()?;
+
+        let a_mask = match self.bmp_header_type {
+            BMPHeaderType::V3 | BMPHeaderType::V4 | BMPHeaderType::V5 => {
+                self.reader.read_u32::<LittleEndian>()?
+            }
+            _ => 0,
+        };
+
+        self.bitfields = match self.image_type {
+            ImageType::Bitfields16 => {
+                Some(Bitfields::from_mask(r_mask, g_mask, b_mask, a_mask, 16)?)
+            }
+            ImageType::Bitfields32 => {
+                Some(Bitfields::from_mask(r_mask, g_mask, b_mask, a_mask, 32)?)
+            }
+            _ => None,
+        };
+
+        if self.bitfields.is_some() && a_mask != 0 {
+            self.add_alpha_channel = true;
+        }
+
+        Ok(())
+    }
+
+    fn read_metadata(&mut self) -> ImageResult<()> {
+        if !self.has_loaded_metadata {
+            self.read_file_header()?;
+            let bmp_header_offset = self.reader.stream_position()?;
+            let bmp_header_size = self.reader.read_u32::<LittleEndian>()?;
+            let bmp_header_end = bmp_header_offset + u64::from(bmp_header_size);
+
+            self.bmp_header_type = match bmp_header_size {
+                BITMAPCOREHEADER_SIZE => BMPHeaderType::Core,
+                BITMAPINFOHEADER_SIZE => BMPHeaderType::Info,
+                BITMAPV2HEADER_SIZE => BMPHeaderType::V2,
+                BITMAPV3HEADER_SIZE => BMPHeaderType::V3,
+                BITMAPV4HEADER_SIZE => BMPHeaderType::V4,
+                BITMAPV5HEADER_SIZE => BMPHeaderType::V5,
+                _ if bmp_header_size < BITMAPCOREHEADER_SIZE => {
+                    // Size of any valid header types won't be smaller than core header type.
+                    return Err(DecoderError::HeaderTooSmall(bmp_header_size).into());
+                }
+                _ => {
+                    return Err(ImageError::Unsupported(
+                        UnsupportedError::from_format_and_kind(
+                            ImageFormat::Bmp.into(),
+                            UnsupportedErrorKind::GenericFeature(format!(
+                                "Unknown bitmap header type (size={})",
+                                bmp_header_size
+                            )),
+                        ),
+                    ))
+                }
+            };
+
+            match self.bmp_header_type {
+                BMPHeaderType::Core => {
+                    self.read_bitmap_core_header()?;
+                }
+                BMPHeaderType::Info
+                | BMPHeaderType::V2
+                | BMPHeaderType::V3
+                | BMPHeaderType::V4
+                | BMPHeaderType::V5 => {
+                    self.read_bitmap_info_header()?;
+                }
+            };
+
+            match self.image_type {
+                ImageType::Bitfields16 | ImageType::Bitfields32 => self.read_bitmasks()?,
+                _ => {}
+            };
+
+            self.reader.seek(SeekFrom::Start(bmp_header_end))?;
+
+            match self.image_type {
+                ImageType::Palette | ImageType::RLE4 | ImageType::RLE8 => self.read_palette()?,
+                _ => {}
+            };
+
+            if self.no_file_header {
+                // Use the offset of the end of metadata instead of reading a BMP file header.
+                self.data_offset = self.reader.stream_position()?;
+            }
+
+            self.has_loaded_metadata = true;
+        }
+        Ok(())
+    }
+
+    #[cfg(feature = "ico")]
+    #[doc(hidden)]
+    pub fn read_metadata_in_ico_format(&mut self) -> ImageResult<()> {
+        self.no_file_header = true;
+        self.add_alpha_channel = true;
+        self.read_metadata()?;
+
+        // The height field in an ICO file is doubled to account for the AND mask
+        // (whether or not an AND mask is actually present).
+        self.height /= 2;
+        Ok(())
+    }
+
+    fn get_palette_size(&mut self) -> ImageResult<usize> {
+        match self.colors_used {
+            0 => Ok(1 << self.bit_count),
+            _ => {
+                if self.colors_used > 1 << self.bit_count {
+                    return Err(DecoderError::PaletteSizeExceeded {
+                        colors_used: self.colors_used,
+                        bit_count: self.bit_count,
+                    }
+                    .into());
+                }
+                Ok(self.colors_used as usize)
+            }
+        }
+    }
+
+    fn bytes_per_color(&self) -> usize {
+        match self.bmp_header_type {
+            BMPHeaderType::Core => 3,
+            _ => 4,
+        }
+    }
+
+    fn read_palette(&mut self) -> ImageResult<()> {
+        const MAX_PALETTE_SIZE: usize = 256; // Palette indices are u8.
+
+        let bytes_per_color = self.bytes_per_color();
+        let palette_size = self.get_palette_size()?;
+        let max_length = MAX_PALETTE_SIZE * bytes_per_color;
+
+        let length = palette_size * bytes_per_color;
+        let mut buf = Vec::with_capacity(max_length);
+
+        // Resize and read the palette entries to the buffer.
+        // We limit the buffer to at most 256 colours to avoid any oom issues as
+        // 8-bit images can't reference more than 256 indexes anyhow.
+        buf.resize(cmp::min(length, max_length), 0);
+        self.reader.by_ref().read_exact(&mut buf)?;
+
+        // Allocate 256 entries even if palette_size is smaller, to prevent corrupt files from
+        // causing an out-of-bounds array access.
+        match length.cmp(&max_length) {
+            Ordering::Greater => {
+                self.reader
+                    .seek(SeekFrom::Current((length - max_length) as i64))?;
+            }
+            Ordering::Less => buf.resize(max_length, 0),
+            Ordering::Equal => (),
+        }
+
+        let p: Vec<[u8; 3]> = (0..MAX_PALETTE_SIZE)
+            .map(|i| {
+                let b = buf[bytes_per_color * i];
+                let g = buf[bytes_per_color * i + 1];
+                let r = buf[bytes_per_color * i + 2];
+                [r, g, b]
+            })
+            .collect();
+
+        self.palette = Some(p);
+
+        Ok(())
+    }
+
+    /// Get the palette that is embedded in the BMP image, if any.
+    pub fn get_palette(&self) -> Option<&[[u8; 3]]> {
+        self.palette.as_ref().map(|vec| &vec[..])
+    }
+
+    fn num_channels(&self) -> usize {
+        if self.indexed_color {
+            1
+        } else if self.add_alpha_channel {
+            4
+        } else {
+            3
+        }
+    }
+
+    fn rows<'a>(&self, pixel_data: &'a mut [u8]) -> RowIterator<'a> {
+        let stride = self.width as usize * self.num_channels();
+        if self.top_down {
+            RowIterator {
+                chunks: Chunker::FromTop(pixel_data.chunks_mut(stride)),
+            }
+        } else {
+            RowIterator {
+                chunks: Chunker::FromBottom(pixel_data.chunks_mut(stride).rev()),
+            }
+        }
+    }
+
+    fn read_palettized_pixel_data(&mut self, buf: &mut [u8]) -> ImageResult<()> {
+        let num_channels = self.num_channels();
+        let row_byte_length = ((i32::from(self.bit_count) * self.width + 31) / 32 * 4) as usize;
+        let mut indices = vec![0; row_byte_length];
+        let palette = self.palette.as_ref().unwrap();
+        let bit_count = self.bit_count;
+        let reader = &mut self.reader;
+        let width = self.width as usize;
+        let skip_palette = self.indexed_color;
+
+        reader.seek(SeekFrom::Start(self.data_offset))?;
+
+        if num_channels == 4 {
+            buf.chunks_exact_mut(4).for_each(|c| c[3] = 0xFF);
+        }
+
+        with_rows(
+            buf,
+            self.width,
+            self.height,
+            num_channels,
+            self.top_down,
+            |row| {
+                reader.read_exact(&mut indices)?;
+                if skip_palette {
+                    row.clone_from_slice(&indices[0..width]);
+                } else {
+                    let mut pixel_iter = row.chunks_mut(num_channels);
+                    match bit_count {
+                        1 => {
+                            set_1bit_pixel_run(&mut pixel_iter, palette, indices.iter());
+                        }
+                        2 => {
+                            set_2bit_pixel_run(&mut pixel_iter, palette, indices.iter(), width);
+                        }
+                        4 => {
+                            set_4bit_pixel_run(&mut pixel_iter, palette, indices.iter(), width);
+                        }
+                        8 => {
+                            set_8bit_pixel_run(&mut pixel_iter, palette, indices.iter(), width);
+                        }
+                        _ => panic!(),
+                    };
+                }
+                Ok(())
+            },
+        )?;
+
+        Ok(())
+    }
+
+    fn read_16_bit_pixel_data(
+        &mut self,
+        buf: &mut [u8],
+        bitfields: Option<&Bitfields>,
+    ) -> ImageResult<()> {
+        let num_channels = self.num_channels();
+        let row_padding_len = self.width as usize % 2 * 2;
+        let row_padding = &mut [0; 2][..row_padding_len];
+        let bitfields = match bitfields {
+            Some(b) => b,
+            None => self.bitfields.as_ref().unwrap(),
+        };
+        let reader = &mut self.reader;
+
+        reader.seek(SeekFrom::Start(self.data_offset))?;
+
+        with_rows(
+            buf,
+            self.width,
+            self.height,
+            num_channels,
+            self.top_down,
+            |row| {
+                for pixel in row.chunks_mut(num_channels) {
+                    let data = u32::from(reader.read_u16::<LittleEndian>()?);
+
+                    pixel[0] = bitfields.r.read(data);
+                    pixel[1] = bitfields.g.read(data);
+                    pixel[2] = bitfields.b.read(data);
+                    if num_channels == 4 {
+                        if bitfields.a.len != 0 {
+                            pixel[3] = bitfields.a.read(data);
+                        } else {
+                            pixel[3] = 0xFF;
+                        }
+                    }
+                }
+                reader.read_exact(row_padding)
+            },
+        )?;
+
+        Ok(())
+    }
+
+    /// Read image data from a reader in 32-bit formats that use bitfields.
+    fn read_32_bit_pixel_data(&mut self, buf: &mut [u8]) -> ImageResult<()> {
+        let num_channels = self.num_channels();
+
+        let bitfields = self.bitfields.as_ref().unwrap();
+
+        let reader = &mut self.reader;
+        reader.seek(SeekFrom::Start(self.data_offset))?;
+
+        with_rows(
+            buf,
+            self.width,
+            self.height,
+            num_channels,
+            self.top_down,
+            |row| {
+                for pixel in row.chunks_mut(num_channels) {
+                    let data = reader.read_u32::<LittleEndian>()?;
+
+                    pixel[0] = bitfields.r.read(data);
+                    pixel[1] = bitfields.g.read(data);
+                    pixel[2] = bitfields.b.read(data);
+                    if num_channels == 4 {
+                        if bitfields.a.len != 0 {
+                            pixel[3] = bitfields.a.read(data);
+                        } else {
+                            pixel[3] = 0xff;
+                        }
+                    }
+                }
+                Ok(())
+            },
+        )?;
+
+        Ok(())
+    }
+
+    /// Read image data from a reader where the colours are stored as 8-bit values (24 or 32-bit).
+    fn read_full_byte_pixel_data(
+        &mut self,
+        buf: &mut [u8],
+        format: &FormatFullBytes,
+    ) -> ImageResult<()> {
+        let num_channels = self.num_channels();
+        let row_padding_len = match *format {
+            FormatFullBytes::RGB24 => (4 - (self.width as usize * 3) % 4) % 4,
+            _ => 0,
+        };
+        let row_padding = &mut [0; 4][..row_padding_len];
+
+        self.reader.seek(SeekFrom::Start(self.data_offset))?;
+
+        let reader = &mut self.reader;
+
+        with_rows(
+            buf,
+            self.width,
+            self.height,
+            num_channels,
+            self.top_down,
+            |row| {
+                for pixel in row.chunks_mut(num_channels) {
+                    if *format == FormatFullBytes::Format888 {
+                        reader.read_u8()?;
+                    }
+
+                    // Read the colour values (b, g, r).
+                    // Reading 3 bytes and reversing them is significantly faster than reading one
+                    // at a time.
+                    reader.read_exact(&mut pixel[0..3])?;
+                    pixel[0..3].reverse();
+
+                    if *format == FormatFullBytes::RGB32 {
+                        reader.read_u8()?;
+                    }
+
+                    // Read the alpha channel if present
+                    if *format == FormatFullBytes::RGBA32 {
+                        reader.read_exact(&mut pixel[3..4])?;
+                    } else if num_channels == 4 {
+                        pixel[3] = 0xFF;
+                    }
+                }
+                reader.read_exact(row_padding)
+            },
+        )?;
+
+        Ok(())
+    }
+
+    fn read_rle_data(&mut self, buf: &mut [u8], image_type: ImageType) -> ImageResult<()> {
+        // Seek to the start of the actual image data.
+        self.reader.seek(SeekFrom::Start(self.data_offset))?;
+
+        let num_channels = self.num_channels();
+        let p = self.palette.as_ref().unwrap();
+
+        // Handling deltas in the RLE scheme means that we need to manually
+        // iterate through rows and pixels.  Even if we didn't have to handle
+        // deltas, we have to ensure that a single runlength doesn't straddle
+        // two rows.
+        let mut row_iter = self.rows(buf);
+
+        while let Some(row) = row_iter.next() {
+            let mut pixel_iter = row.chunks_mut(num_channels);
+
+            let mut x = 0;
+            loop {
+                let instruction = {
+                    let control_byte = self.reader.read_u8()?;
+                    match control_byte {
+                        RLE_ESCAPE => {
+                            let op = self.reader.read_u8()?;
+
+                            match op {
+                                RLE_ESCAPE_EOL => RLEInsn::EndOfRow,
+                                RLE_ESCAPE_EOF => RLEInsn::EndOfFile,
+                                RLE_ESCAPE_DELTA => {
+                                    let xdelta = self.reader.read_u8()?;
+                                    let ydelta = self.reader.read_u8()?;
+                                    RLEInsn::Delta(xdelta, ydelta)
+                                }
+                                _ => {
+                                    let mut length = op as usize;
+                                    if self.image_type == ImageType::RLE4 {
+                                        length = (length + 1) / 2;
+                                    }
+                                    length += length & 1;
+                                    let mut buffer = vec![0; length];
+                                    self.reader.read_exact(&mut buffer)?;
+                                    RLEInsn::Absolute(op, buffer)
+                                }
+                            }
+                        }
+                        _ => {
+                            let palette_index = self.reader.read_u8()?;
+                            RLEInsn::PixelRun(control_byte, palette_index)
+                        }
+                    }
+                };
+
+                match instruction {
+                    RLEInsn::EndOfFile => {
+                        pixel_iter.for_each(|p| p.fill(0));
+                        row_iter.for_each(|r| r.fill(0));
+                        return Ok(());
+                    }
+                    RLEInsn::EndOfRow => {
+                        pixel_iter.for_each(|p| p.fill(0));
+                        break;
+                    }
+                    RLEInsn::Delta(x_delta, y_delta) => {
+                        // The msdn site on bitmap compression doesn't specify
+                        // what happens to the values skipped when encountering
+                        // a delta code, however IE and the windows image
+                        // preview seems to replace them with black pixels,
+                        // so we stick to that.
+
+                        if y_delta > 0 {
+                            // Zero out the remainder of the current row.
+                            pixel_iter.for_each(|p| p.fill(0));
+
+                            // If any full rows are skipped, zero them out.
+                            for _ in 1..y_delta {
+                                let row = row_iter.next().ok_or(DecoderError::CorruptRleData)?;
+                                row.fill(0);
+                            }
+
+                            // Set the pixel iterator to the start of the next row.
+                            pixel_iter = row_iter
+                                .next()
+                                .ok_or(DecoderError::CorruptRleData)?
+                                .chunks_mut(num_channels);
+
+                            // Zero out the pixels up to the current point in the row.
+                            for _ in 0..x {
+                                pixel_iter
+                                    .next()
+                                    .ok_or(DecoderError::CorruptRleData)?
+                                    .fill(0);
+                            }
+                        }
+
+                        for _ in 0..x_delta {
+                            let pixel = pixel_iter.next().ok_or(DecoderError::CorruptRleData)?;
+                            pixel.fill(0);
+                        }
+                        x += x_delta as usize;
+                    }
+                    RLEInsn::Absolute(length, indices) => {
+                        // Absolute mode cannot span rows, so if we run
+                        // out of pixels to process, we should stop
+                        // processing the image.
+                        match image_type {
+                            ImageType::RLE8 => {
+                                if !set_8bit_pixel_run(
+                                    &mut pixel_iter,
+                                    p,
+                                    indices.iter(),
+                                    length as usize,
+                                ) {
+                                    return Err(DecoderError::CorruptRleData.into());
+                                }
+                            }
+                            ImageType::RLE4 => {
+                                if !set_4bit_pixel_run(
+                                    &mut pixel_iter,
+                                    p,
+                                    indices.iter(),
+                                    length as usize,
+                                ) {
+                                    return Err(DecoderError::CorruptRleData.into());
+                                }
+                            }
+                            _ => unreachable!(),
+                        }
+                        x += length as usize;
+                    }
+                    RLEInsn::PixelRun(n_pixels, palette_index) => {
+                        // A pixel run isn't allowed to span rows, but we
+                        // simply continue on to the next row if we run
+                        // out of pixels to set.
+                        match image_type {
+                            ImageType::RLE8 => {
+                                if !set_8bit_pixel_run(
+                                    &mut pixel_iter,
+                                    p,
+                                    repeat(&palette_index),
+                                    n_pixels as usize,
+                                ) {
+                                    return Err(DecoderError::CorruptRleData.into());
+                                }
+                            }
+                            ImageType::RLE4 => {
+                                if !set_4bit_pixel_run(
+                                    &mut pixel_iter,
+                                    p,
+                                    repeat(&palette_index),
+                                    n_pixels as usize,
+                                ) {
+                                    return Err(DecoderError::CorruptRleData.into());
+                                }
+                            }
+                            _ => unreachable!(),
+                        }
+                        x += n_pixels as usize;
+                    }
+                }
+            }
+        }
+
+        Ok(())
+    }
+
+    /// Read the actual data of the image. This function is deliberately not public because it
+    /// cannot be called multiple times without seeking back the underlying reader in between.
+    pub(crate) fn read_image_data(&mut self, buf: &mut [u8]) -> ImageResult<()> {
+        match self.image_type {
+            ImageType::Palette => self.read_palettized_pixel_data(buf),
+            ImageType::RGB16 => self.read_16_bit_pixel_data(buf, Some(&R5_G5_B5_COLOR_MASK)),
+            ImageType::RGB24 => self.read_full_byte_pixel_data(buf, &FormatFullBytes::RGB24),
+            ImageType::RGB32 => self.read_full_byte_pixel_data(buf, &FormatFullBytes::RGB32),
+            ImageType::RGBA32 => self.read_full_byte_pixel_data(buf, &FormatFullBytes::RGBA32),
+            ImageType::RLE8 => self.read_rle_data(buf, ImageType::RLE8),
+            ImageType::RLE4 => self.read_rle_data(buf, ImageType::RLE4),
+            ImageType::Bitfields16 => match self.bitfields {
+                Some(_) => self.read_16_bit_pixel_data(buf, None),
+                None => Err(DecoderError::BitfieldMasksMissing(16).into()),
+            },
+            ImageType::Bitfields32 => match self.bitfields {
+                Some(R8_G8_B8_COLOR_MASK) => {
+                    self.read_full_byte_pixel_data(buf, &FormatFullBytes::Format888)
+                }
+                Some(R8_G8_B8_A8_COLOR_MASK) => {
+                    self.read_full_byte_pixel_data(buf, &FormatFullBytes::RGBA32)
+                }
+                Some(_) => self.read_32_bit_pixel_data(buf),
+                None => Err(DecoderError::BitfieldMasksMissing(32).into()),
+            },
+        }
+    }
+}
+
+/// Wrapper struct around a `Cursor<Vec<u8>>`
+pub struct BmpReader<R>(Cursor<Vec<u8>>, PhantomData<R>);
+impl<R> Read for BmpReader<R> {
+    fn read(&mut self, buf: &mut [u8]) -> io::Result<usize> {
+        self.0.read(buf)
+    }
+    fn read_to_end(&mut self, buf: &mut Vec<u8>) -> io::Result<usize> {
+        if self.0.position() == 0 && buf.is_empty() {
+            mem::swap(buf, self.0.get_mut());
+            Ok(buf.len())
+        } else {
+            self.0.read_to_end(buf)
+        }
+    }
+}
+
+impl<'a, R: 'a + Read + Seek> ImageDecoder<'a> for BmpDecoder<R> {
+    type Reader = BmpReader<R>;
+
+    fn dimensions(&self) -> (u32, u32) {
+        (self.width as u32, self.height as u32)
+    }
+
+    fn color_type(&self) -> ColorType {
+        if self.indexed_color {
+            ColorType::L8
+        } else if self.add_alpha_channel {
+            ColorType::Rgba8
+        } else {
+            ColorType::Rgb8
+        }
+    }
+
+    fn into_reader(self) -> ImageResult<Self::Reader> {
+        Ok(BmpReader(
+            Cursor::new(image::decoder_to_vec(self)?),
+            PhantomData,
+        ))
+    }
+
+    fn read_image(mut self, buf: &mut [u8]) -> ImageResult<()> {
+        assert_eq!(u64::try_from(buf.len()), Ok(self.total_bytes()));
+        self.read_image_data(buf)
+    }
+}
+
+impl<'a, R: 'a + Read + Seek> ImageDecoderRect<'a> for BmpDecoder<R> {
+    fn read_rect_with_progress<F: Fn(Progress)>(
+        &mut self,
+        x: u32,
+        y: u32,
+        width: u32,
+        height: u32,
+        buf: &mut [u8],
+        progress_callback: F,
+    ) -> ImageResult<()> {
+        let start = self.reader.stream_position()?;
+        image::load_rect(
+            x,
+            y,
+            width,
+            height,
+            buf,
+            progress_callback,
+            self,
+            |_, _| Ok(()),
+            |s, buf| s.read_image_data(buf),
+        )?;
+        self.reader.seek(SeekFrom::Start(start))?;
+        Ok(())
+    }
+}
+
+#[cfg(test)]
+mod test {
+    use super::*;
+
+    #[test]
+    fn test_bitfield_len() {
+        for len in 1..9 {
+            let bitfield = Bitfield { shift: 0, len };
+            for i in 0..(1 << len) {
+                let read = bitfield.read(i);
+                let calc = (i as f64 / ((1 << len) - 1) as f64 * 255f64).round() as u8;
+                if read != calc {
+                    println!("len:{} i:{} read:{} calc:{}", len, i, read, calc);
+                }
+                assert_eq!(read, calc);
+            }
+        }
+    }
+
+    #[test]
+    fn read_rect() {
+        let f = std::fs::File::open("tests/images/bmp/images/Core_8_Bit.bmp").unwrap();
+        let mut decoder = super::BmpDecoder::new(f).unwrap();
+
+        let mut buf: Vec<u8> = vec![0; 8 * 8 * 3];
+        decoder.read_rect(0, 0, 8, 8, &mut *buf).unwrap();
+    }
+
+    #[test]
+    fn read_rle_too_short() {
+        let data = vec![
+            0x42, 0x4d, 0x04, 0xee, 0xfe, 0xff, 0xff, 0x10, 0xff, 0x00, 0x04, 0x00, 0x00, 0x00,
+            0x7c, 0x00, 0x00, 0x00, 0x0c, 0x41, 0x00, 0x00, 0x07, 0x10, 0x00, 0x00, 0x01, 0x00,
+            0x04, 0x00, 0x02, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x0d, 0x00, 0x00, 0x00,
+            0x00, 0x80, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0xff, 0xff, 0xff, 0xff, 0xfe, 0x21,
+            0xff, 0x00, 0x66, 0x61, 0x72, 0x62, 0x66, 0x65, 0x6c, 0x64, 0x00, 0x00, 0x00, 0x00,
+            0x00, 0x00, 0x00, 0xff, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+            0xff, 0xd8, 0xff, 0x00, 0x00, 0x19, 0x51, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+            0x00, 0x00, 0x00, 0x10, 0x00, 0x00, 0x00, 0x00, 0x00, 0xfa, 0xff, 0x00, 0x00, 0x00,
+            0x00, 0x01, 0x00, 0x11, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x0f, 0x00,
+            0x00, 0x00, 0x00, 0x2d, 0x31, 0x31, 0x35, 0x36, 0x00, 0xff, 0x00, 0x00, 0x52, 0x3a,
+            0x37, 0x30, 0x7e, 0x71, 0x63, 0x91, 0x5a, 0x04, 0x00, 0x10, 0x00, 0x00, 0x00, 0x00,
+            0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x04, 0x00, 0x00, 0x00, 0x00, 0x00,
+            0x01, 0x00, 0x00, 0x00, 0x00, 0x00, 0x2d, 0x35, 0x37, 0x00, 0xff, 0x00, 0x00, 0x52,
+            0x3a, 0x37, 0x30, 0x7e, 0x71, 0x63, 0x91, 0x5a, 0x04, 0x05, 0x3c, 0x00, 0x00, 0x11,
+            0x00, 0x5d, 0x7a, 0x82, 0xb7, 0xca, 0x2d, 0x31, 0xff, 0xff, 0xc7, 0x95, 0x33, 0x2e,
+            0x00, 0x00, 0x00, 0x01, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x7c, 0x00,
+            0x20, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x20, 0x66, 0x00, 0x4d,
+            0x4d, 0x00, 0x2a, 0x00,
+        ];
+
+        let decoder = BmpDecoder::new(Cursor::new(&data)).unwrap();
+        let mut buf = vec![0; usize::try_from(decoder.total_bytes()).unwrap()];
+        assert!(decoder.read_image(&mut buf).is_ok());
+    }
+
+    #[test]
+    fn test_no_header() {
+        let tests = [
+            "Info_R8_G8_B8.bmp",
+            "Info_A8_R8_G8_B8.bmp",
+            "Info_8_Bit.bmp",
+            "Info_4_Bit.bmp",
+            "Info_1_Bit.bmp",
+        ];
+
+        for name in &tests {
+            let path = format!("tests/images/bmp/images/{name}");
+            let ref_img = crate::open(&path).unwrap();
+            let mut data = std::fs::read(&path).unwrap();
+            // skip the BITMAPFILEHEADER
+            let slice = &mut data[14..];
+            let decoder = BmpDecoder::new_without_file_header(Cursor::new(slice)).unwrap();
+            let no_hdr_img = crate::DynamicImage::from_decoder(decoder).unwrap();
+            assert_eq!(ref_img, no_hdr_img);
+        }
+    }
+}