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Fix issues with 2-bit and 1-bit per pixel interlaced images [ci skip]

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This commit is contained in:
Joshua Holmer 2016-03-30 21:42:33 -04:00
parent 5740867be5
commit 7280ca80ce
1 changed files with 8 additions and 11 deletions
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19
src/png.rs
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@ -157,27 +157,27 @@ impl<'a> Iterator for ScanLines<'a> {
let y_steps; let y_steps;
match self.pass { match self.pass {
Some((1, _)) => { Some((1, _)) => {
bits_per_line >>= 3; bits_per_line = (bits_per_line as f32 / 8f32).ceil() as usize;
y_steps = 8; y_steps = 8;
} }
Some((2, _)) => { Some((2, _)) => {
bits_per_line >>= 3; bits_per_line = (bits_per_line as f32 / 8f32).ceil() as usize;
y_steps = 8; y_steps = 8;
} }
Some((3, _)) => { Some((3, _)) => {
bits_per_line >>= 2; bits_per_line = (bits_per_line as f32 / 4f32).ceil() as usize;
y_steps = 8; y_steps = 8;
} }
Some((4, _)) => { Some((4, _)) => {
bits_per_line >>= 2; bits_per_line = (bits_per_line as f32 / 4f32).ceil() as usize;
y_steps = 4; y_steps = 4;
} }
Some((5, _)) => { Some((5, _)) => {
bits_per_line >>= 1; bits_per_line = (bits_per_line as f32 / 2f32).ceil() as usize;
y_steps = 4; y_steps = 4;
} }
Some((6, _)) => { Some((6, _)) => {
bits_per_line >>= 1; bits_per_line = (bits_per_line as f32 / 2f32).ceil() as usize;
y_steps = 2; y_steps = 2;
} }
Some((7, _)) => { Some((7, _)) => {
@ -201,11 +201,9 @@ impl<'a> Iterator for ScanLines<'a> {
bits_per_line -= gap; bits_per_line -= gap;
} }
} }
// Round up without converting to float let bytes_per_line = (bits_per_line as f32 / 8f32).ceil() as usize;
let bytes_per_line = (bits_per_line + bits_per_line % 8) >> 3;
self.start = self.end; self.start = self.end;
self.end = self.start + bytes_per_line + 1; self.end = self.start + bytes_per_line + 1;
// TODO: Handle 4x4 pixel images
if let Some(pass) = self.pass.as_mut() { if let Some(pass) = self.pass.as_mut() {
if pass.1 + y_steps >= self.png.ihdr_data.height { if pass.1 + y_steps >= self.png.ihdr_data.height {
pass.0 += 1; pass.0 += 1;
@ -228,8 +226,7 @@ impl<'a> Iterator for ScanLines<'a> {
let bits_per_line = self.png.ihdr_data.width as usize * let bits_per_line = self.png.ihdr_data.width as usize *
self.png.ihdr_data.bit_depth.as_u8() as usize * self.png.ihdr_data.bit_depth.as_u8() as usize *
self.png.channels_per_pixel() as usize; self.png.channels_per_pixel() as usize;
// Round up without converting to float let bytes_per_line = (bits_per_line as f32 / 8f32).ceil() as usize;
let bytes_per_line = (bits_per_line + bits_per_line % 8) >> 3;
self.start = self.end; self.start = self.end;
self.end = self.start + bytes_per_line + 1; self.end = self.start + bytes_per_line + 1;
Some(ScanLine { Some(ScanLine {