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authorpommicket <pommicket@gmail.com>2023-09-07 15:18:45 -0400
committerpommicket <pommicket@gmail.com>2023-09-07 22:49:53 -0400
commit5cad1bee9b72610d9d97b5f97e7f1a245a2d2ba5 (patch)
tree5ee6f155f6900be4eeec07ad33417d2d9992a80f /colors.c
parent815d652b570f53c989f62d0c7db847d7d6dfd940 (diff)
more diagnostics
Diffstat (limited to 'colors.c')
-rw-r--r--colors.c30
1 files changed, 30 insertions, 0 deletions
diff --git a/colors.c b/colors.c
index 3e704e9..d9ef7aa 100644
--- a/colors.c
+++ b/colors.c
@@ -169,3 +169,33 @@ u32 color_apply_opacity(u32 color, float opacity) {
opacity = clampf(opacity, 0.0f, 1.0f);
return (color & 0xffffff00) | (u32)((color & 0xff) * opacity);
}
+
+
+static float color_relative_luminance(const float rgb[3]) {
+ // see https://www.w3.org/TR/2008/REC-WCAG20-20081211/#relativeluminancedef
+ float c[3];
+ for (int i = 0; i < 3; ++i) {
+ const float x = rgb[i];
+ c[i] = x <= 0.03928f ? x * (1.0f / 12.92f) : powf((x + 0.055f) * (1.0f / 1.055f), 2.4f);
+ }
+ return 0.2126f * c[0] + 0.7152f * c[1] + 0.0722f * c[2];
+}
+
+float color_contrast_ratio(const float rgb1[3], const float rgb2[3]) {
+ // see https://www.w3.org/TR/2008/REC-WCAG20-20081211/#contrast-ratiodef
+ float l1 = color_relative_luminance(rgb1);
+ float l2 = color_relative_luminance(rgb2);
+ if (l1 < l2) {
+ float temp = l1;
+ l1 = l2;
+ l2 = temp;
+ }
+ return (l1 + 0.05f) / (l2 + 0.05f);
+}
+
+float color_contrast_ratio_u32(u32 color1, u32 color2) {
+ float rgb1[4], rgb2[4];
+ rgba_u32_to_floats(color1, rgb1);
+ rgba_u32_to_floats(color2, rgb2);
+ return color_contrast_ratio(rgb1, rgb2);
+}