diff options
Diffstat (limited to 'vendor/tiff/src/encoder/compression/packbits.rs')
| -rw-r--r-- | vendor/tiff/src/encoder/compression/packbits.rs | 214 |
1 files changed, 0 insertions, 214 deletions
diff --git a/vendor/tiff/src/encoder/compression/packbits.rs b/vendor/tiff/src/encoder/compression/packbits.rs deleted file mode 100644 index 7ba3833..0000000 --- a/vendor/tiff/src/encoder/compression/packbits.rs +++ /dev/null @@ -1,214 +0,0 @@ -use crate::{encoder::compression::*, tags::CompressionMethod}; -use std::io::{BufWriter, Error, ErrorKind, Write}; - -/// Compressor that uses the Packbits[^note] algorithm to compress bytes. -/// -/// [^note]: PackBits is often ineffective on continuous tone images, -/// including many grayscale images. In such cases, it is better -/// to leave the image uncompressed. -#[derive(Debug, Clone, Copy, PartialEq, Eq, Default)] -pub struct Packbits; - -impl Compression for Packbits { - const COMPRESSION_METHOD: CompressionMethod = CompressionMethod::PackBits; - - fn get_algorithm(&self) -> Compressor { - Compressor::Packbits(*self) - } -} - -impl CompressionAlgorithm for Packbits { - fn write_to<W: Write>(&mut self, writer: &mut W, bytes: &[u8]) -> Result<u64, io::Error> { - // Inspired by https://github.com/skirridsystems/packbits - - const MIN_REPT: u8 = 3; // Minimum run to compress between differ blocks - const MAX_BYTES: u8 = 128; // Maximum number of bytes that can be encoded in a header byte - - // Encoding for header byte based on number of bytes represented. - fn encode_diff(n: u8) -> u8 { - n - 1 - } - fn encode_rept(n: u8) -> u8 { - let var = 256 - (n - 1) as u16; - var as u8 - } - - fn write_u8<W: Write>(writer: &mut W, byte: u8) -> Result<u64, Error> { - writer.write(&[byte]).map(|byte_count| byte_count as u64) - } - - let mut bufwriter = BufWriter::new(writer); - let mut bytes_written = 0u64; // The number of bytes written into the writer - let mut offset: Option<u64> = None; // The index of the first byte written into the writer - - let mut src_index: usize = 0; // Index of the current byte - let mut src_count = bytes.len(); //The number of bytes remaining to be compressed - - let mut in_run = false; // Indication whether counting of similar bytes is performed - let mut run_index = 0u8; // Distance into pending bytes that a run starts - - let mut bytes_pending = 0u8; // Bytes looked at but not yet output - let mut pending_index = 0usize; // Index of the first pending byte - - let mut curr_byte: u8; // Byte currently being considered - let mut last_byte: u8; // Previous byte - - // Need at least one byte to compress - if src_count == 0 { - return Err(Error::new(ErrorKind::WriteZero, "write zero")); - } - - // Prime compressor with first character. - last_byte = bytes[src_index]; - src_index += 1; - bytes_pending += 1; - - while src_count - 1 != 0 { - src_count -= 1; - curr_byte = bytes[src_index]; - src_index += 1; - bytes_pending += 1; - - if in_run { - if (curr_byte != last_byte) || (bytes_pending > MAX_BYTES) { - offset.get_or_insert(write_u8(&mut bufwriter, encode_rept(bytes_pending - 1))?); - write_u8(&mut bufwriter, last_byte)?; - bytes_written += 2; - - bytes_pending = 1; - pending_index = src_index - 1; - run_index = 0; - in_run = false; - } - } else { - if bytes_pending > MAX_BYTES { - // We have as much differing data as we can output in one chunk. - // Output MAX_BYTES leaving one byte. - offset.get_or_insert(write_u8(&mut bufwriter, encode_diff(MAX_BYTES))?); - bufwriter.write(&bytes[pending_index..pending_index + MAX_BYTES as usize])?; - bytes_written += 1 + MAX_BYTES as u64; - - pending_index += MAX_BYTES as usize; - bytes_pending -= MAX_BYTES; - run_index = bytes_pending - 1; // A run could start here - } else if curr_byte == last_byte { - if (bytes_pending - run_index >= MIN_REPT) || (run_index == 0) { - // This is a worthwhile run - if run_index != 0 { - // Flush differing data out of input buffer - offset.get_or_insert(write_u8(&mut bufwriter, encode_diff(run_index))?); - bufwriter - .write(&bytes[pending_index..pending_index + run_index as usize])?; - bytes_written += 1 + run_index as u64; - } - bytes_pending -= run_index; // Length of run - in_run = true; - } - } else { - run_index = bytes_pending - 1; // A run could start here - } - } - last_byte = curr_byte; - } - - // Output the remainder - if in_run { - bytes_written += 2; - offset.get_or_insert(write_u8(&mut bufwriter, encode_rept(bytes_pending))?); - write_u8(&mut bufwriter, last_byte)?; - } else { - bytes_written += 1 + bytes_pending as u64; - offset.get_or_insert(write_u8(&mut bufwriter, encode_diff(bytes_pending))?); - bufwriter.write(&bytes[pending_index..pending_index + bytes_pending as usize])?; - } - - bufwriter.flush()?; - Ok(bytes_written) - } -} - -#[cfg(test)] -mod tests { - use super::*; - use crate::encoder::compression::tests::TEST_DATA; - use std::io::Cursor; - - #[test] - fn test_packbits_single_byte() { - // compress single byte - const UNCOMPRESSED_DATA: [u8; 1] = [0x3F]; - const EXPECTED_COMPRESSED_DATA: [u8; 2] = [0x00, 0x3F]; - - let mut compressed_data = Vec::<u8>::new(); - let mut writer = Cursor::new(&mut compressed_data); - Packbits::default() - .write_to(&mut writer, &UNCOMPRESSED_DATA) - .unwrap(); - assert_eq!(compressed_data, EXPECTED_COMPRESSED_DATA); - } - - #[test] - fn test_packbits_rept() { - // compress buffer with repetitive sequence - const UNCOMPRESSED_DATA: &'static [u8] = - b"This strrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrring hangs."; - const EXPECTED_COMPRESSED_DATA: &'static [u8] = b"\x06This st\xD1r\x09ing hangs."; - - let mut compressed_data = Vec::<u8>::new(); - let mut writer = Cursor::new(&mut compressed_data); - Packbits::default() - .write_to(&mut writer, UNCOMPRESSED_DATA) - .unwrap(); - assert_eq!(compressed_data, EXPECTED_COMPRESSED_DATA); - } - - #[test] - fn test_packbits_large_rept_nonrept() { - // compress buffer with large repetitive and non-repetitive sequence - let mut data = b"This st".to_vec(); - for _i in 0..158 { - data.push(b'r'); - } - data.extend_from_slice(b"ing hangs."); - for i in 0..158 { - data.push(i); - } - - const EXPECTED_COMPRESSED_DATA: [u8; 182] = [ - 0x06, 0x54, 0x68, 0x69, 0x73, 0x20, 0x73, 0x74, 0x81, 0x72, 0xE3, 0x72, 0x7F, 0x69, - 0x6E, 0x67, 0x20, 0x68, 0x61, 0x6E, 0x67, 0x73, 0x2E, 0x00, 0x01, 0x02, 0x03, 0x04, - 0x05, 0x06, 0x07, 0x08, 0x09, 0x0A, 0x0B, 0x0C, 0x0D, 0x0E, 0x0F, 0x10, 0x11, 0x12, - 0x13, 0x14, 0x15, 0x16, 0x17, 0x18, 0x19, 0x1A, 0x1B, 0x1C, 0x1D, 0x1E, 0x1F, 0x20, - 0x21, 0x22, 0x23, 0x24, 0x25, 0x26, 0x27, 0x28, 0x29, 0x2A, 0x2B, 0x2C, 0x2D, 0x2E, - 0x2F, 0x30, 0x31, 0x32, 0x33, 0x34, 0x35, 0x36, 0x37, 0x38, 0x39, 0x3A, 0x3B, 0x3C, - 0x3D, 0x3E, 0x3F, 0x40, 0x41, 0x42, 0x43, 0x44, 0x45, 0x46, 0x47, 0x48, 0x49, 0x4A, - 0x4B, 0x4C, 0x4D, 0x4E, 0x4F, 0x50, 0x51, 0x52, 0x53, 0x54, 0x55, 0x56, 0x57, 0x58, - 0x59, 0x5A, 0x5B, 0x5C, 0x5D, 0x5E, 0x5F, 0x60, 0x61, 0x62, 0x63, 0x64, 0x65, 0x66, - 0x67, 0x68, 0x69, 0x6A, 0x6B, 0x6C, 0x6D, 0x6E, 0x6F, 0x70, 0x71, 0x72, 0x73, 0x74, - 0x75, 0x27, 0x76, 0x77, 0x78, 0x79, 0x7A, 0x7B, 0x7C, 0x7D, 0x7E, 0x7F, 0x80, 0x81, - 0x82, 0x83, 0x84, 0x85, 0x86, 0x87, 0x88, 0x89, 0x8A, 0x8B, 0x8C, 0x8D, 0x8E, 0x8F, - 0x90, 0x91, 0x92, 0x93, 0x94, 0x95, 0x96, 0x97, 0x98, 0x99, 0x9A, 0x9B, 0x9C, 0x9D, - ]; - - let mut compressed_data = Vec::<u8>::new(); - let mut writer = Cursor::new(&mut compressed_data); - Packbits::default() - .write_to(&mut writer, data.as_slice()) - .unwrap(); - assert_eq!(compressed_data, EXPECTED_COMPRESSED_DATA); - } - - #[test] - fn test_packbits() { - // compress teststring - const EXPECTED_COMPRESSED_DATA: &'static [u8] = - b"\x3CThis is a string for checking various compression algorithms."; - - let mut compressed_data = Vec::<u8>::new(); - let mut writer = Cursor::new(&mut compressed_data); - Packbits::default() - .write_to(&mut writer, TEST_DATA) - .unwrap(); - assert_eq!(compressed_data, EXPECTED_COMPRESSED_DATA); - } -} |