More accurate 8-bit <=> 5-bit RGB color conversion (#1827)

2025-11-20 10:12:06 +00:00 · 2025-09-08 15:13:25 -04:00
parent 65d408eb5d
commit 223b3d1921
20 changed files with 31 additions and 15 deletions
--- a/test/gfx/alpha_embedded.err
+++ b/test/gfx/alpha_embedded.err
@@ -1,4 +1,4 @@
-error: Failed to fit tile colors [$1527, $15cc, $1ab4] in specified palettes
+error: Failed to fit tile colors [$1527, $15cc, $1a93] in specified palettes
 note: The following palette was specified:
-        [$1ab4, $15cc]
+        [$1a93, $15cc]
 Conversion aborted after 1 error
--- a/test/gfx/at-file-ref.err
+++ b/test/gfx/at-file-ref.err
@@ -1,4 +1,4 @@
-error: Failed to fit tile colors [$6c8a, $7f55, $7fff] in specified palettes
+error: Failed to fit tile colors [$688b, $7f55, $7fff] in specified palettes
 note: The following palettes were specified:
        [$5f77, $213d, $41a6, $40ee]
        [$3f65, $36b3, $262a, $50b0]
--- a/test/gfx/bad_manual_pals.err
+++ b/test/gfx/bad_manual_pals.err
@@ -1,5 +1,5 @@
-error: Failed to fit tile colors [$6c8a, $7f55, $7fff] in specified palettes
+error: Failed to fit tile colors [$688b, $7f55, $7fff] in specified palettes
 note: The following palettes were specified:
        [$7fff, $7f55]
-        [$7fff, $6c8a]
+        [$7fff, $688b]
 Conversion aborted after 1 error
--- a/test/gfx/base_ids.out.pal
+++ b/test/gfx/base_ids.out.pal
--- a/test/gfx/bg_fuse.err
+++ b/test/gfx/bg_fuse.err
@@ -1,3 +1,3 @@
-warning: Fusing colors #a9b9c9ff and #aabbccff into Game Boy color $66f5 [first seen at x: 1, y: 1]
+warning: Fusing colors #a9bacbff and #aabbccff into Game Boy color $66f5 [first seen at x: 1, y: 1]
 FATAL: Tile (0, 0) contains the background color (#aabbccff)!
 Conversion aborted after 1 error
--- a/test/gfx/bg_fuse.png
+++ b/test/gfx/bg_fuse.png
--- a/test/gfx/empty_lines.out.pal
+++ b/test/gfx/empty_lines.out.pal
@@ -1 +1 @@
-妉U<EFBFBD><EFBFBD><EFBFBD>
+媓U<EFBFBD><EFBFBD><EFBFBD>
--- a/test/gfx/full_aco.out.pal
+++ b/test/gfx/full_aco.out.pal
--- a/test/gfx/full_aco.png
+++ b/test/gfx/full_aco.png
--- a/test/gfx/full_act.out.pal
+++ b/test/gfx/full_act.out.pal
--- a/test/gfx/full_act.png
+++ b/test/gfx/full_act.png
--- a/test/gfx/full_gpl.out.pal
+++ b/test/gfx/full_gpl.out.pal
--- a/test/gfx/full_gpl.png
+++ b/test/gfx/full_gpl.png
--- a/test/gfx/full_psp.out.pal
+++ b/test/gfx/full_psp.out.pal
--- a/test/gfx/full_psp.png
+++ b/test/gfx/full_psp.png
--- a/test/gfx/interlaced.out.pal
+++ b/test/gfx/interlaced.out.pal
--- a/test/gfx/randtilegen.cpp
+++ b/test/gfx/randtilegen.cpp
@@ -144,7 +144,7 @@ static void generate_palettes(uint16_t palettes[/* 60 */][4]) {
 * Expand a 5-bit color component to 8 bits with minimal bias
 */
 static uint8_t _5to8(uint8_t five) {
-	return five << 3 | five >> 2;
+	return (five * 255 + 15) / 31;
 }

 // Can't mark as `const`, as the array type is otherwise not compatible (augh)