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Improve palette downgrading

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This commit is contained in:
Joshua Holmer 2016-02-19 14:48:52 -05:00
parent 5c0bbbe2bb
commit 677ce14b96
1 changed files with 9 additions and 3 deletions
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12
src/png.rs
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@ -708,7 +708,7 @@ fn reduce_bit_depth_8_or_less(png: &PngData) -> Option<(Vec<u8>, u8)> {
}
for line in png.scan_lines() {
// I hate having to iterate twice...
// FIXME: I hate having to iterate twice...
reduced.extend(BitVec::from_bytes(&[line.filter]));
let bit_vec = BitVec::from_bytes(&line.data);
for (i, bit) in bit_vec.iter().enumerate() {
@ -862,6 +862,7 @@ fn reduce_palette_to_grayscale(png: &PngData) -> Option<Vec<u8>> {
let mut reduced = BitVec::with_capacity(png.raw_data.len() * 8);
let mut cur_pixel = Vec::with_capacity(3);
let palette = png.palette.clone().unwrap();
// Iterate through palette and determine if all colors are grayscale
for byte in &palette {
cur_pixel.push(*byte);
if cur_pixel.len() == 3 {
@ -874,21 +875,26 @@ fn reduce_palette_to_grayscale(png: &PngData) -> Option<Vec<u8>> {
}
}
// Iterate through scanlines and assign grayscale value to each pixel
let bit_depth: usize = png.ihdr_data.bit_depth.as_u8() as usize;
for line in png.scan_lines() {
reduced.extend(BitVec::from_bytes(&[line.filter]));
let bit_vec = BitVec::from_bytes(&line.data);
let mut cur_pixel = BitVec::with_capacity(bit_depth);
for bit in bit_vec {
// Handle bit depths less than 8-bits
// At the end of each pixel, push its grayscale value onto the reduced image
cur_pixel.push(bit);
if cur_pixel.len() == bit_depth {
let palette_idx: usize = ((cur_pixel.to_bytes()[0] - 1) * 3) as usize;
let palette_idx: usize = ((cur_pixel.to_bytes()[0]) * 3) as usize;
reduced.extend(BitVec::from_bytes(&[palette[palette_idx]]));
// BitVec's clear function doesn't set len to 0
cur_pixel = BitVec::with_capacity(bit_depth);
}
}
}
None
Some(reduced.to_bytes())
}
fn reduce_grayscale_alpha_to_grayscale(png: &PngData) -> Option<Vec<u8>> {