robert/qoicodec
1
0
Fork 0
Code Issues Pull Requests Actions Packages Projects Releases Wiki Activity

Fix: wrapping, store previous pixel value

Browse Source 
The wrapping wasn't working properly, clearly, but I forgot about the
previous pixel entirely.

I'll add some more explicit tests for the previous pixel behavior. I
think it's still broken for RGB and RGBA, because I'm dumb.
This commit is contained in:
Robert Garrett
2024-05-07 09:48:35 -05:00
parent 62b35b5aba
commit b05daa503e
1 changed files with 22 additions and 18 deletions
Download Patch File Download Diff File Expand all files Collapse all files

40
src/main.rs
View File

@@ -134,29 +134,33 @@ where
return Some(self.back_buffer[idx]); return Some(self.back_buffer[idx]);
} }
QOI_OP_DIFF => { QOI_OP_DIFF => {
let dr = ((byte & 0b0011_0000) >> 4) - 2; let dr = ((byte & 0b0011_0000) >> 4).wrapping_sub(2);
let dg = ((byte & 0b0000_1100) >> 2) - 2; let dg = ((byte & 0b0000_1100) >> 2).wrapping_sub(2);
let db = (byte & 0b0000_0011) - 2; let db = (byte & 0b0000_0011).wrapping_sub(2);
return Some(PixelRGBA { let result = PixelRGBA {
r: self.prev_pixel.r + dr, r: self.prev_pixel.r.wrapping_add(dr),
g: self.prev_pixel.g + dg, g: self.prev_pixel.g.wrapping_add(dg),
b: self.prev_pixel.b + db, b: self.prev_pixel.b.wrapping_add(db),
a: self.prev_pixel.a, a: self.prev_pixel.a,
}); };
self.prev_pixel = result;
return Some(result);
} }
QOI_OP_LUMA => { QOI_OP_LUMA => {
let dg = (byte & !QOI_OP_SMALL_MASK) - 32; let dg = (byte & !QOI_OP_SMALL_MASK).wrapping_sub(32);
let packed = self.bytes.next()?; let packed = self.bytes.next()?;
let drdg = ((packed & 0b1111_0000) >> 4) - 8; let drdg = ((packed & 0b1111_0000) >> 4).wrapping_sub(8);
let dbdg = (packed & 0b0000_1111) - 8; let dbdg = (packed & 0b0000_1111).wrapping_sub(8);
let dr = drdg + dg; let dr = drdg.wrapping_add(dg);
let db = dbdg + dg; let db = dbdg.wrapping_add(dg);
return Some(PixelRGBA { let result = PixelRGBA {
r: self.prev_pixel.r + dr, r: self.prev_pixel.r.wrapping_add(dr),
g: self.prev_pixel.g + dg, g: self.prev_pixel.g.wrapping_add(dg),
b: self.prev_pixel.b + db, b: self.prev_pixel.b.wrapping_add(db),
a: self.prev_pixel.a, a: self.prev_pixel.a,
}); };
self.prev_pixel = result;
return Some(result);
} }
QOI_OP_RUN => { QOI_OP_RUN => {
self.run_len = byte & !QOI_OP_SMALL_MASK; self.run_len = byte & !QOI_OP_SMALL_MASK;