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Optimize color cache #89

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Aug 6, 2024
Merged

Optimize color cache #89

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43 changes: 24 additions & 19 deletions src/lossless.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -473,7 +473,6 @@ impl<R: Read> LosslessDecoder<R> {

let huff_index = huffman_info.get_huff_index(0, 0);
let mut tree = &huffman_info.huffman_code_groups[huff_index];
let mut last_cached = 0;
let mut index = 0;

let mut next_block_start = 0;
Expand Down Expand Up @@ -523,15 +522,19 @@ impl<R: Read> LosslessDecoder<R> {
//check code
if code < 256 {
//literal, so just use huffman codes and read as argb
let red = tree[RED].read_symbol(&mut self.bit_reader)?;
let blue = tree[BLUE].read_symbol(&mut self.bit_reader)?;
let alpha = tree[ALPHA].read_symbol(&mut self.bit_reader)?;
let green = code as u8;
let red = tree[RED].read_symbol(&mut self.bit_reader)? as u8;
let blue = tree[BLUE].read_symbol(&mut self.bit_reader)? as u8;
let alpha = tree[ALPHA].read_symbol(&mut self.bit_reader)? as u8;

data[index * 4] = red as u8;
data[index * 4 + 1] = code as u8;
data[index * 4 + 2] = blue as u8;
data[index * 4 + 3] = alpha as u8;
data[index * 4] = red;
data[index * 4 + 1] = green;
data[index * 4 + 2] = blue;
data[index * 4 + 3] = alpha;

if let Some(color_cache) = huffman_info.color_cache.as_mut() {
color_cache.insert([red, green, blue, alpha]);
}
index += 1;
} else if code < 256 + 24 {
//backward reference, so go back and use that to add image data
Expand All @@ -551,26 +554,28 @@ impl<R: Read> LosslessDecoder<R> {
for i in 0..length {
data[index * 4 + i * 4..][..4].copy_from_slice(&value);
}
if let Some(color_cache) = huffman_info.color_cache.as_mut() {
color_cache.insert(value);
}
} else {
for i in 0..length * 4 {
data[index * 4 + i] = data[index * 4 + i - dist * 4];
}
if let Some(color_cache) = huffman_info.color_cache.as_mut() {
for pixel in data[index * 4..][..length * 4].chunks_exact(4) {
color_cache.insert(pixel.try_into().unwrap());
}
}
}
index += length;
} else {
//color cache, so use previously stored pixels to get this pixel
let key = code - 256 - 24;

if let Some(color_cache) = huffman_info.color_cache.as_mut() {
//cache old colors
while last_cached < index {
color_cache.insert(data[last_cached * 4..][..4].try_into().unwrap());
last_cached += 1;
}
data[index * 4..][..4].copy_from_slice(&color_cache.lookup(key.into())?);
} else {
return Err(DecodingError::BitStreamError);
}
let color_cache = huffman_info
.color_cache
.as_mut()
.ok_or(DecodingError::BitStreamError)?;
data[index * 4..][..4].copy_from_slice(&color_cache.lookup(key.into())?);
index += 1;
}
}
Expand Down
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