improve color mapping when dithering

cgytrus · cgytrus · commit 6e2bca2a32db · 2023-08-03T20:27:24.000+03:00
diff --git a/src/util/rgba4444.rs b/src/util/rgba4444.rs
@@ -14,9 +14,10 @@ impl ColorMap for RGBA4444 {
 
 	#[inline(always)]
 	fn map_color(&self, color: &mut Rgba<u8>) {
-		color[0] = (color[0] / 15) * 15;
-		color[1] = (color[1] / 15) * 15;
-		color[2] = (color[2] / 15) * 15;
-		color[3] = (color[3] / 15) * 15;
+		let convert = |x: u8| (x as f32 / 255.0 * 15.0) as u8 * (255 / 15);
+		color[0] = convert(color[0]);
+		color[1] = convert(color[1]);
+		color[2] = convert(color[2]);
+		color[3] = convert(color[3]);
 	}
 }

Original file line number	Diff line number	Diff line change
`@@ -14,9 +14,10 @@ impl ColorMap for RGBA4444 {`
`14`	`14`
`15`	`15`	`#[inline(always)]`
`16`	`16`	`fn map_color(&self, color: &mut Rgba<u8>) {`
`17`		`- color[0] = (color[0] / 15) * 15;`
`18`		`- color[1] = (color[1] / 15) * 15;`
`19`		`- color[2] = (color[2] / 15) * 15;`
`20`		`- color[3] = (color[3] / 15) * 15;`
	`17`	`+ let convert = \|x: u8\| (x as f32 / 255.0 * 15.0) as u8 * (255 / 15);`
	`18`	`+ color[0] = convert(color[0]);`
	`19`	`+ color[1] = convert(color[1]);`
	`20`	`+ color[2] = convert(color[2]);`
	`21`	`+ color[3] = convert(color[3]);`
`21`	`22`	`}`
`22`	`23`	`}`