From a990de90fe41456a23e58bd087d2f107d321f3a1 Mon Sep 17 00:00:00 2001 From: Valentin Popov Date: Fri, 19 Jul 2024 16:37:58 +0400 Subject: Deleted vendor folder --- vendor/image/src/codecs/dxt.rs | 869 ----------------------------------------- 1 file changed, 869 deletions(-) delete mode 100644 vendor/image/src/codecs/dxt.rs (limited to 'vendor/image/src/codecs/dxt.rs') diff --git a/vendor/image/src/codecs/dxt.rs b/vendor/image/src/codecs/dxt.rs deleted file mode 100644 index 8737fb3..0000000 --- a/vendor/image/src/codecs/dxt.rs +++ /dev/null @@ -1,869 +0,0 @@ -//! Decoding of DXT (S3TC) compression -//! -//! DXT is an image format that supports lossy compression -//! -//! # Related Links -//! * - Description of the DXT compression OpenGL extensions. -//! -//! Note: this module only implements bare DXT encoding/decoding, it does not parse formats that can contain DXT files like .dds - -use std::convert::TryFrom; -use std::io::{self, Read, Seek, SeekFrom, Write}; - -use crate::color::ColorType; -use crate::error::{ImageError, ImageResult, ParameterError, ParameterErrorKind}; -use crate::image::{self, ImageDecoder, ImageDecoderRect, ImageReadBuffer, Progress}; - -/// What version of DXT compression are we using? -/// Note that DXT2 and DXT4 are left away as they're -/// just DXT3 and DXT5 with premultiplied alpha -#[derive(Clone, Copy, Debug, PartialEq, Eq)] -pub enum DxtVariant { - /// The DXT1 format. 48 bytes of RGB data in a 4x4 pixel square is - /// compressed into an 8 byte block of DXT1 data - DXT1, - /// The DXT3 format. 64 bytes of RGBA data in a 4x4 pixel square is - /// compressed into a 16 byte block of DXT3 data - DXT3, - /// The DXT5 format. 64 bytes of RGBA data in a 4x4 pixel square is - /// compressed into a 16 byte block of DXT5 data - DXT5, -} - -impl DxtVariant { - /// Returns the amount of bytes of raw image data - /// that is encoded in a single DXTn block - fn decoded_bytes_per_block(self) -> usize { - match self { - DxtVariant::DXT1 => 48, - DxtVariant::DXT3 | DxtVariant::DXT5 => 64, - } - } - - /// Returns the amount of bytes per block of encoded DXTn data - fn encoded_bytes_per_block(self) -> usize { - match self { - DxtVariant::DXT1 => 8, - DxtVariant::DXT3 | DxtVariant::DXT5 => 16, - } - } - - /// Returns the color type that is stored in this DXT variant - pub fn color_type(self) -> ColorType { - match self { - DxtVariant::DXT1 => ColorType::Rgb8, - DxtVariant::DXT3 | DxtVariant::DXT5 => ColorType::Rgba8, - } - } -} - -/// DXT decoder -pub struct DxtDecoder { - inner: R, - width_blocks: u32, - height_blocks: u32, - variant: DxtVariant, - row: u32, -} - -impl DxtDecoder { - /// Create a new DXT decoder that decodes from the stream ```r```. - /// As DXT is often stored as raw buffers with the width/height - /// somewhere else the width and height of the image need - /// to be passed in ```width``` and ```height```, as well as the - /// DXT variant in ```variant```. - /// width and height are required to be powers of 2 and at least 4. - /// otherwise an error will be returned - pub fn new( - r: R, - width: u32, - height: u32, - variant: DxtVariant, - ) -> Result, ImageError> { - if width % 4 != 0 || height % 4 != 0 { - // TODO: this is actually a bit of a weird case. We could return `DecodingError` but - // it's not really the format that is wrong However, the encoder should surely return - // `EncodingError` so it would be the logical choice for symmetry. - return Err(ImageError::Parameter(ParameterError::from_kind( - ParameterErrorKind::DimensionMismatch, - ))); - } - let width_blocks = width / 4; - let height_blocks = height / 4; - Ok(DxtDecoder { - inner: r, - width_blocks, - height_blocks, - variant, - row: 0, - }) - } - - fn read_scanline(&mut self, buf: &mut [u8]) -> io::Result { - assert_eq!(u64::try_from(buf.len()), Ok(self.scanline_bytes())); - - let mut src = - vec![0u8; self.variant.encoded_bytes_per_block() * self.width_blocks as usize]; - self.inner.read_exact(&mut src)?; - match self.variant { - DxtVariant::DXT1 => decode_dxt1_row(&src, buf), - DxtVariant::DXT3 => decode_dxt3_row(&src, buf), - DxtVariant::DXT5 => decode_dxt5_row(&src, buf), - } - self.row += 1; - Ok(buf.len()) - } -} - -// Note that, due to the way that DXT compression works, a scanline is considered to consist out of -// 4 lines of pixels. -impl<'a, R: 'a + Read> ImageDecoder<'a> for DxtDecoder { - type Reader = DxtReader; - - fn dimensions(&self) -> (u32, u32) { - (self.width_blocks * 4, self.height_blocks * 4) - } - - fn color_type(&self) -> ColorType { - self.variant.color_type() - } - - fn scanline_bytes(&self) -> u64 { - self.variant.decoded_bytes_per_block() as u64 * u64::from(self.width_blocks) - } - - fn into_reader(self) -> ImageResult { - Ok(DxtReader { - buffer: ImageReadBuffer::new(self.scanline_bytes(), self.total_bytes()), - decoder: self, - }) - } - - fn read_image(mut self, buf: &mut [u8]) -> ImageResult<()> { - assert_eq!(u64::try_from(buf.len()), Ok(self.total_bytes())); - - for chunk in buf.chunks_mut(self.scanline_bytes().max(1) as usize) { - self.read_scanline(chunk)?; - } - Ok(()) - } -} - -impl<'a, R: 'a + Read + Seek> ImageDecoderRect<'a> for DxtDecoder { - fn read_rect_with_progress( - &mut self, - x: u32, - y: u32, - width: u32, - height: u32, - buf: &mut [u8], - progress_callback: F, - ) -> ImageResult<()> { - let encoded_scanline_bytes = - self.variant.encoded_bytes_per_block() as u64 * u64::from(self.width_blocks); - - let start = self.inner.stream_position()?; - image::load_rect( - x, - y, - width, - height, - buf, - progress_callback, - self, - |s, scanline| { - s.inner - .seek(SeekFrom::Start(start + scanline * encoded_scanline_bytes))?; - Ok(()) - }, - |s, buf| s.read_scanline(buf).map(|_| ()), - )?; - self.inner.seek(SeekFrom::Start(start))?; - Ok(()) - } -} - -/// DXT reader -pub struct DxtReader { - buffer: ImageReadBuffer, - decoder: DxtDecoder, -} - -impl Read for DxtReader { - fn read(&mut self, buf: &mut [u8]) -> io::Result { - let decoder = &mut self.decoder; - self.buffer.read(buf, |buf| decoder.read_scanline(buf)) - } -} - -/// DXT encoder -pub struct DxtEncoder { - w: W, -} - -impl DxtEncoder { - /// Create a new encoder that writes its output to ```w``` - pub fn new(w: W) -> DxtEncoder { - DxtEncoder { w } - } - - /// Encodes the image data ```data``` - /// that has dimensions ```width``` and ```height``` - /// in ```DxtVariant``` ```variant``` - /// data is assumed to be in variant.color_type() - pub fn encode( - mut self, - data: &[u8], - width: u32, - height: u32, - variant: DxtVariant, - ) -> ImageResult<()> { - if width % 4 != 0 || height % 4 != 0 { - // TODO: this is not very idiomatic yet. Should return an EncodingError. - return Err(ImageError::Parameter(ParameterError::from_kind( - ParameterErrorKind::DimensionMismatch, - ))); - } - let width_blocks = width / 4; - let height_blocks = height / 4; - - let stride = variant.decoded_bytes_per_block(); - - assert!(data.len() >= width_blocks as usize * height_blocks as usize * stride); - - for chunk in data.chunks(width_blocks as usize * stride) { - let data = match variant { - DxtVariant::DXT1 => encode_dxt1_row(chunk), - DxtVariant::DXT3 => encode_dxt3_row(chunk), - DxtVariant::DXT5 => encode_dxt5_row(chunk), - }; - self.w.write_all(&data)?; - } - Ok(()) - } -} - -/** - * Actual encoding/decoding logic below. - */ -use std::mem::swap; - -type Rgb = [u8; 3]; - -/// decodes a 5-bit R, 6-bit G, 5-bit B 16-bit packed color value into 8-bit RGB -/// mapping is done so min/max range values are preserved. So for 5-bit -/// values 0x00 -> 0x00 and 0x1F -> 0xFF -fn enc565_decode(value: u16) -> Rgb { - let red = (value >> 11) & 0x1F; - let green = (value >> 5) & 0x3F; - let blue = (value) & 0x1F; - [ - (red * 0xFF / 0x1F) as u8, - (green * 0xFF / 0x3F) as u8, - (blue * 0xFF / 0x1F) as u8, - ] -} - -/// encodes an 8-bit RGB value into a 5-bit R, 6-bit G, 5-bit B 16-bit packed color value -/// mapping preserves min/max values. It is guaranteed that i == encode(decode(i)) for all i -fn enc565_encode(rgb: Rgb) -> u16 { - let red = (u16::from(rgb[0]) * 0x1F + 0x7E) / 0xFF; - let green = (u16::from(rgb[1]) * 0x3F + 0x7E) / 0xFF; - let blue = (u16::from(rgb[2]) * 0x1F + 0x7E) / 0xFF; - (red << 11) | (green << 5) | blue -} - -/// utility function: squares a value -fn square(a: i32) -> i32 { - a * a -} - -/// returns the squared error between two RGB values -fn diff(a: Rgb, b: Rgb) -> i32 { - square(i32::from(a[0]) - i32::from(b[0])) - + square(i32::from(a[1]) - i32::from(b[1])) - + square(i32::from(a[2]) - i32::from(b[2])) -} - -/* - * Functions for decoding DXT compression - */ - -/// Constructs the DXT5 alpha lookup table from the two alpha entries -/// if alpha0 > alpha1, constructs a table of [a0, a1, 6 linearly interpolated values from a0 to a1] -/// if alpha0 <= alpha1, constructs a table of [a0, a1, 4 linearly interpolated values from a0 to a1, 0, 0xFF] -fn alpha_table_dxt5(alpha0: u8, alpha1: u8) -> [u8; 8] { - let mut table = [alpha0, alpha1, 0, 0, 0, 0, 0, 0xFF]; - if alpha0 > alpha1 { - for i in 2..8u16 { - table[i as usize] = - (((8 - i) * u16::from(alpha0) + (i - 1) * u16::from(alpha1)) / 7) as u8; - } - } else { - for i in 2..6u16 { - table[i as usize] = - (((6 - i) * u16::from(alpha0) + (i - 1) * u16::from(alpha1)) / 5) as u8; - } - } - table -} - -/// decodes an 8-byte dxt color block into the RGB channels of a 16xRGB or 16xRGBA block. -/// source should have a length of 8, dest a length of 48 (RGB) or 64 (RGBA) -fn decode_dxt_colors(source: &[u8], dest: &mut [u8], is_dxt1: bool) { - // sanity checks, also enable the compiler to elide all following bound checks - assert!(source.len() == 8 && (dest.len() == 48 || dest.len() == 64)); - // calculate pitch to store RGB values in dest (3 for RGB, 4 for RGBA) - let pitch = dest.len() / 16; - - // extract color data - let color0 = u16::from(source[0]) | (u16::from(source[1]) << 8); - let color1 = u16::from(source[2]) | (u16::from(source[3]) << 8); - let color_table = u32::from(source[4]) - | (u32::from(source[5]) << 8) - | (u32::from(source[6]) << 16) - | (u32::from(source[7]) << 24); - // let color_table = source[4..8].iter().rev().fold(0, |t, &b| (t << 8) | b as u32); - - // decode the colors to rgb format - let mut colors = [[0; 3]; 4]; - colors[0] = enc565_decode(color0); - colors[1] = enc565_decode(color1); - - // determine color interpolation method - if color0 > color1 || !is_dxt1 { - // linearly interpolate the other two color table entries - for i in 0..3 { - colors[2][i] = ((u16::from(colors[0][i]) * 2 + u16::from(colors[1][i]) + 1) / 3) as u8; - colors[3][i] = ((u16::from(colors[0][i]) + u16::from(colors[1][i]) * 2 + 1) / 3) as u8; - } - } else { - // linearly interpolate one other entry, keep the other at 0 - for i in 0..3 { - colors[2][i] = ((u16::from(colors[0][i]) + u16::from(colors[1][i]) + 1) / 2) as u8; - } - } - - // serialize the result. Every color is determined by looking up - // two bits in color_table which identify which color to actually pick from the 4 possible colors - for i in 0..16 { - dest[i * pitch..i * pitch + 3] - .copy_from_slice(&colors[(color_table >> (i * 2)) as usize & 3]); - } -} - -/// Decodes a 16-byte bock of dxt5 data to a 16xRGBA block -fn decode_dxt5_block(source: &[u8], dest: &mut [u8]) { - assert!(source.len() == 16 && dest.len() == 64); - - // extract alpha index table (stored as little endian 64-bit value) - let alpha_table = source[2..8] - .iter() - .rev() - .fold(0, |t, &b| (t << 8) | u64::from(b)); - - // alhpa level decode - let alphas = alpha_table_dxt5(source[0], source[1]); - - // serialize alpha - for i in 0..16 { - dest[i * 4 + 3] = alphas[(alpha_table >> (i * 3)) as usize & 7]; - } - - // handle colors - decode_dxt_colors(&source[8..16], dest, false); -} - -/// Decodes a 16-byte bock of dxt3 data to a 16xRGBA block -fn decode_dxt3_block(source: &[u8], dest: &mut [u8]) { - assert!(source.len() == 16 && dest.len() == 64); - - // extract alpha index table (stored as little endian 64-bit value) - let alpha_table = source[0..8] - .iter() - .rev() - .fold(0, |t, &b| (t << 8) | u64::from(b)); - - // serialize alpha (stored as 4-bit values) - for i in 0..16 { - dest[i * 4 + 3] = ((alpha_table >> (i * 4)) as u8 & 0xF) * 0x11; - } - - // handle colors - decode_dxt_colors(&source[8..16], dest, false); -} - -/// Decodes a 8-byte bock of dxt5 data to a 16xRGB block -fn decode_dxt1_block(source: &[u8], dest: &mut [u8]) { - assert!(source.len() == 8 && dest.len() == 48); - decode_dxt_colors(source, dest, true); -} - -/// Decode a row of DXT1 data to four rows of RGB data. -/// source.len() should be a multiple of 8, otherwise this panics. -fn decode_dxt1_row(source: &[u8], dest: &mut [u8]) { - assert!(source.len() % 8 == 0); - let block_count = source.len() / 8; - assert!(dest.len() >= block_count * 48); - - // contains the 16 decoded pixels per block - let mut decoded_block = [0u8; 48]; - - for (x, encoded_block) in source.chunks(8).enumerate() { - decode_dxt1_block(encoded_block, &mut decoded_block); - - // copy the values from the decoded block to linewise RGB layout - for line in 0..4 { - let offset = (block_count * line + x) * 12; - dest[offset..offset + 12].copy_from_slice(&decoded_block[line * 12..(line + 1) * 12]); - } - } -} - -/// Decode a row of DXT3 data to four rows of RGBA data. -/// source.len() should be a multiple of 16, otherwise this panics. -fn decode_dxt3_row(source: &[u8], dest: &mut [u8]) { - assert!(source.len() % 16 == 0); - let block_count = source.len() / 16; - assert!(dest.len() >= block_count * 64); - - // contains the 16 decoded pixels per block - let mut decoded_block = [0u8; 64]; - - for (x, encoded_block) in source.chunks(16).enumerate() { - decode_dxt3_block(encoded_block, &mut decoded_block); - - // copy the values from the decoded block to linewise RGB layout - for line in 0..4 { - let offset = (block_count * line + x) * 16; - dest[offset..offset + 16].copy_from_slice(&decoded_block[line * 16..(line + 1) * 16]); - } - } -} - -/// Decode a row of DXT5 data to four rows of RGBA data. -/// source.len() should be a multiple of 16, otherwise this panics. -fn decode_dxt5_row(source: &[u8], dest: &mut [u8]) { - assert!(source.len() % 16 == 0); - let block_count = source.len() / 16; - assert!(dest.len() >= block_count * 64); - - // contains the 16 decoded pixels per block - let mut decoded_block = [0u8; 64]; - - for (x, encoded_block) in source.chunks(16).enumerate() { - decode_dxt5_block(encoded_block, &mut decoded_block); - - // copy the values from the decoded block to linewise RGB layout - for line in 0..4 { - let offset = (block_count * line + x) * 16; - dest[offset..offset + 16].copy_from_slice(&decoded_block[line * 16..(line + 1) * 16]); - } - } -} - -/* - * Functions for encoding DXT compression - */ - -/// Tries to perform the color encoding part of dxt compression -/// the approach taken is simple, it picks unique combinations -/// of the colors present in the block, and attempts to encode the -/// block with each, picking the encoding that yields the least -/// squared error out of all of them. -/// -/// This could probably be faster but is already reasonably fast -/// and a good reference impl to optimize others against. -/// -/// Another way to perform this analysis would be to perform a -/// singular value decomposition of the different colors, and -/// then pick 2 points on this line as the base colors. But -/// this is still rather unwieldy math and has issues -/// with the 3-linear-colors-and-0 case, it's also worse -/// at conserving the original colors. -/// -/// source: should be RGBAx16 or RGBx16 bytes of data, -/// dest 8 bytes of resulting encoded color data -fn encode_dxt_colors(source: &[u8], dest: &mut [u8], is_dxt1: bool) { - // sanity checks and determine stride when parsing the source data - assert!((source.len() == 64 || source.len() == 48) && dest.len() == 8); - let stride = source.len() / 16; - - // reference colors array - let mut colors = [[0u8; 3]; 4]; - - // Put the colors we're going to be processing in an array with pure RGB layout - // note: we reverse the pixel order here. The reason for this is found in the inner quantization loop. - let mut targets = [[0u8; 3]; 16]; - for (s, d) in source.chunks(stride).rev().zip(&mut targets) { - *d = [s[0], s[1], s[2]]; - } - - // roundtrip all colors through the r5g6b5 encoding - for rgb in &mut targets { - *rgb = enc565_decode(enc565_encode(*rgb)); - } - - // and deduplicate the set of colors to choose from as the algorithm is O(N^2) in this - let mut colorspace_ = [[0u8; 3]; 16]; - let mut colorspace_len = 0; - for color in &targets { - if !colorspace_[..colorspace_len].contains(color) { - colorspace_[colorspace_len] = *color; - colorspace_len += 1; - } - } - let mut colorspace = &colorspace_[..colorspace_len]; - - // in case of slight gradients it can happen that there's only one entry left in the color table. - // as the resulting banding can be quite bad if we would just left the block at the closest - // encodable color, we have a special path here that tries to emulate the wanted color - // using the linear interpolation between gradients - if colorspace.len() == 1 { - // the base color we got from colorspace reduction - let ref_rgb = colorspace[0]; - // the unreduced color in this block that's the furthest away from the actual block - let mut rgb = targets - .iter() - .cloned() - .max_by_key(|rgb| diff(*rgb, ref_rgb)) - .unwrap(); - // amplify differences by 2.5, which should push them to the next quantized value - // if possible without overshoot - for i in 0..3 { - rgb[i] = - ((i16::from(rgb[i]) - i16::from(ref_rgb[i])) * 5 / 2 + i16::from(ref_rgb[i])) as u8; - } - - // roundtrip it through quantization - let encoded = enc565_encode(rgb); - let rgb = enc565_decode(encoded); - - // in case this didn't land us a different color the best way to represent this field is - // as a single color block - if rgb == ref_rgb { - dest[0] = encoded as u8; - dest[1] = (encoded >> 8) as u8; - - for d in dest.iter_mut().take(8).skip(2) { - *d = 0; - } - return; - } - - // we did find a separate value: add it to the options so after one round of quantization - // we're done - colorspace_[1] = rgb; - colorspace = &colorspace_[..2]; - } - - // block quantization loop: we basically just try every possible combination, returning - // the combination with the least squared error - // stores the best candidate colors - let mut chosen_colors = [[0; 3]; 4]; - // did this index table use the [0,0,0] variant - let mut chosen_use_0 = false; - // error calculated for the last entry - let mut chosen_error = 0xFFFF_FFFFu32; - - // loop through unique permutations of the colorspace, where c1 != c2 - 'search: for (i, &c1) in colorspace.iter().enumerate() { - colors[0] = c1; - - for &c2 in &colorspace[0..i] { - colors[1] = c2; - - if is_dxt1 { - // what's inside here is ran at most 120 times. - for use_0 in 0..2 { - // and 240 times here. - - if use_0 != 0 { - // interpolate one color, set the other to 0 - for i in 0..3 { - colors[2][i] = - ((u16::from(colors[0][i]) + u16::from(colors[1][i]) + 1) / 2) as u8; - } - colors[3] = [0, 0, 0]; - } else { - // interpolate to get 2 more colors - for i in 0..3 { - colors[2][i] = - ((u16::from(colors[0][i]) * 2 + u16::from(colors[1][i]) + 1) / 3) - as u8; - colors[3][i] = - ((u16::from(colors[0][i]) + u16::from(colors[1][i]) * 2 + 1) / 3) - as u8; - } - } - - // calculate the total error if we were to quantize the block with these color combinations - // both these loops have statically known iteration counts and are well vectorizable - // note that the inside of this can be run about 15360 times worst case, i.e. 960 times per - // pixel. - let total_error = targets - .iter() - .map(|t| colors.iter().map(|c| diff(*c, *t) as u32).min().unwrap()) - .sum(); - - // update the match if we found a better one - if total_error < chosen_error { - chosen_colors = colors; - chosen_use_0 = use_0 != 0; - chosen_error = total_error; - - // if we've got a perfect or at most 1 LSB off match, we're done - if total_error < 4 { - break 'search; - } - } - } - } else { - // what's inside here is ran at most 120 times. - - // interpolate to get 2 more colors - for i in 0..3 { - colors[2][i] = - ((u16::from(colors[0][i]) * 2 + u16::from(colors[1][i]) + 1) / 3) as u8; - colors[3][i] = - ((u16::from(colors[0][i]) + u16::from(colors[1][i]) * 2 + 1) / 3) as u8; - } - - // calculate the total error if we were to quantize the block with these color combinations - // both these loops have statically known iteration counts and are well vectorizable - // note that the inside of this can be run about 15360 times worst case, i.e. 960 times per - // pixel. - let total_error = targets - .iter() - .map(|t| colors.iter().map(|c| diff(*c, *t) as u32).min().unwrap()) - .sum(); - - // update the match if we found a better one - if total_error < chosen_error { - chosen_colors = colors; - chosen_error = total_error; - - // if we've got a perfect or at most 1 LSB off match, we're done - if total_error < 4 { - break 'search; - } - } - } - } - } - - // calculate the final indices - // note that targets is already in reverse pixel order, to make the index computation easy. - let mut chosen_indices = 0u32; - for t in &targets { - let (idx, _) = chosen_colors - .iter() - .enumerate() - .min_by_key(|&(_, c)| diff(*c, *t)) - .unwrap(); - chosen_indices = (chosen_indices << 2) | idx as u32; - } - - // encode the colors - let mut color0 = enc565_encode(chosen_colors[0]); - let mut color1 = enc565_encode(chosen_colors[1]); - - // determine encoding. Note that color0 == color1 is impossible at this point - if is_dxt1 { - if color0 > color1 { - if chosen_use_0 { - swap(&mut color0, &mut color1); - // Indexes are packed 2 bits wide, swap index 0/1 but preserve 2/3. - let filter = (chosen_indices & 0xAAAA_AAAA) >> 1; - chosen_indices ^= filter ^ 0x5555_5555; - } - } else if !chosen_use_0 { - swap(&mut color0, &mut color1); - // Indexes are packed 2 bits wide, swap index 0/1 and 2/3. - chosen_indices ^= 0x5555_5555; - } - } - - // encode everything. - dest[0] = color0 as u8; - dest[1] = (color0 >> 8) as u8; - dest[2] = color1 as u8; - dest[3] = (color1 >> 8) as u8; - for i in 0..4 { - dest[i + 4] = (chosen_indices >> (i * 8)) as u8; - } -} - -/// Encodes a buffer of 16 alpha bytes into a dxt5 alpha index table, -/// where the alpha table they are indexed against is created by -/// calling alpha_table_dxt5(alpha0, alpha1) -/// returns the resulting error and alpha table -fn encode_dxt5_alpha(alpha0: u8, alpha1: u8, alphas: &[u8; 16]) -> (i32, u64) { - // create a table for the given alpha ranges - let table = alpha_table_dxt5(alpha0, alpha1); - let mut indices = 0u64; - let mut total_error = 0i32; - - // least error brute force search - for (i, &a) in alphas.iter().enumerate() { - let (index, error) = table - .iter() - .enumerate() - .map(|(i, &e)| (i, square(i32::from(e) - i32::from(a)))) - .min_by_key(|&(_, e)| e) - .unwrap(); - total_error += error; - indices |= (index as u64) << (i * 3); - } - - (total_error, indices) -} - -/// Encodes a RGBAx16 sequence of bytes to a 16 bytes DXT5 block -fn encode_dxt5_block(source: &[u8], dest: &mut [u8]) { - assert!(source.len() == 64 && dest.len() == 16); - - // perform dxt color encoding - encode_dxt_colors(source, &mut dest[8..16], false); - - // copy out the alpha bytes - let mut alphas = [0; 16]; - for i in 0..16 { - alphas[i] = source[i * 4 + 3]; - } - - // try both alpha compression methods, see which has the least error. - let alpha07 = alphas.iter().cloned().min().unwrap(); - let alpha17 = alphas.iter().cloned().max().unwrap(); - let (error7, indices7) = encode_dxt5_alpha(alpha07, alpha17, &alphas); - - // if all alphas are 0 or 255 it doesn't particularly matter what we do here. - let alpha05 = alphas - .iter() - .cloned() - .filter(|&i| i != 255) - .max() - .unwrap_or(255); - let alpha15 = alphas - .iter() - .cloned() - .filter(|&i| i != 0) - .min() - .unwrap_or(0); - let (error5, indices5) = encode_dxt5_alpha(alpha05, alpha15, &alphas); - - // pick the best one, encode the min/max values - let mut alpha_table = if error5 < error7 { - dest[0] = alpha05; - dest[1] = alpha15; - indices5 - } else { - dest[0] = alpha07; - dest[1] = alpha17; - indices7 - }; - - // encode the alphas - for byte in dest[2..8].iter_mut() { - *byte = alpha_table as u8; - alpha_table >>= 8; - } -} - -/// Encodes a RGBAx16 sequence of bytes into a 16 bytes DXT3 block -fn encode_dxt3_block(source: &[u8], dest: &mut [u8]) { - assert!(source.len() == 64 && dest.len() == 16); - - // perform dxt color encoding - encode_dxt_colors(source, &mut dest[8..16], false); - - // DXT3 alpha compression is very simple, just round towards the nearest value - - // index the alpha values into the 64bit alpha table - let mut alpha_table = 0u64; - for i in 0..16 { - let alpha = u64::from(source[i * 4 + 3]); - let alpha = (alpha + 0x8) / 0x11; - alpha_table |= alpha << (i * 4); - } - - // encode the alpha values - for byte in &mut dest[0..8] { - *byte = alpha_table as u8; - alpha_table >>= 8; - } -} - -/// Encodes a RGBx16 sequence of bytes into a 8 bytes DXT1 block -fn encode_dxt1_block(source: &[u8], dest: &mut [u8]) { - assert!(source.len() == 48 && dest.len() == 8); - - // perform dxt color encoding - encode_dxt_colors(source, dest, true); -} - -/// Decode a row of DXT1 data to four rows of RGBA data. -/// source.len() should be a multiple of 8, otherwise this panics. -fn encode_dxt1_row(source: &[u8]) -> Vec { - assert!(source.len() % 48 == 0); - let block_count = source.len() / 48; - - let mut dest = vec![0u8; block_count * 8]; - // contains the 16 decoded pixels per block - let mut decoded_block = [0u8; 48]; - - for (x, encoded_block) in dest.chunks_mut(8).enumerate() { - // copy the values from the decoded block to linewise RGB layout - for line in 0..4 { - let offset = (block_count * line + x) * 12; - decoded_block[line * 12..(line + 1) * 12].copy_from_slice(&source[offset..offset + 12]); - } - - encode_dxt1_block(&decoded_block, encoded_block); - } - dest -} - -/// Decode a row of DXT3 data to four rows of RGBA data. -/// source.len() should be a multiple of 16, otherwise this panics. -fn encode_dxt3_row(source: &[u8]) -> Vec { - assert!(source.len() % 64 == 0); - let block_count = source.len() / 64; - - let mut dest = vec![0u8; block_count * 16]; - // contains the 16 decoded pixels per block - let mut decoded_block = [0u8; 64]; - - for (x, encoded_block) in dest.chunks_mut(16).enumerate() { - // copy the values from the decoded block to linewise RGB layout - for line in 0..4 { - let offset = (block_count * line + x) * 16; - decoded_block[line * 16..(line + 1) * 16].copy_from_slice(&source[offset..offset + 16]); - } - - encode_dxt3_block(&decoded_block, encoded_block); - } - dest -} - -/// Decode a row of DXT5 data to four rows of RGBA data. -/// source.len() should be a multiple of 16, otherwise this panics. -fn encode_dxt5_row(source: &[u8]) -> Vec { - assert!(source.len() % 64 == 0); - let block_count = source.len() / 64; - - let mut dest = vec![0u8; block_count * 16]; - // contains the 16 decoded pixels per block - let mut decoded_block = [0u8; 64]; - - for (x, encoded_block) in dest.chunks_mut(16).enumerate() { - // copy the values from the decoded block to linewise RGB layout - for line in 0..4 { - let offset = (block_count * line + x) * 16; - decoded_block[line * 16..(line + 1) * 16].copy_from_slice(&source[offset..offset + 16]); - } - - encode_dxt5_block(&decoded_block, encoded_block); - } - dest -} -- cgit v1.2.3