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render/color: add wlr_color_transform_eval()

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Makes it so the Vulkan renderer can handle arbitrary color
transforms, and doesn't need to be updated each time a new one is
added.
This commit is contained in:
Simon Ser 2025-06-15 15:00:21 +02:00
parent d786e07899
commit 3d36ab9211
4 changed files with 82 additions and 25 deletions
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76
render/color.c
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@ -108,6 +108,65 @@ struct wlr_color_transform_lut_3x1d *color_transform_lut_3x1d_from_base(
return lut_3x1d;
}
static float srgb_eval_inverse_eotf(float x) {
// See https://www.w3.org/Graphics/Color/srgb
if (x <= 0.0031308) {
return 12.92 * x;
} else {
return 1.055 * powf(x, 1.0 / 2.4) - 0.055;
}
}
static float st2084_pq_eval_inverse_eotf(float x) {
// H.273 TransferCharacteristics code point 16
float c1 = 0.8359375;
float c2 = 18.8515625;
float c3 = 18.6875;
float m = 78.84375;
float n = 0.1593017578125;
if (x < 0) {
x = 0;
}
if (x > 1) {
x = 1;
}
float pow_n = powf(x, n);
return powf((c1 + c2 * pow_n) / (1 + c3 * pow_n), m);
}
static float bt1886_eval_inverse_eotf(float x) {
float lb = powf(0.0001, 1.0 / 2.4);
float lw = powf(1.0, 1.0 / 2.4);
float a = powf(lw - lb, 2.4);
float b = lb / (lw - lb);
return powf(x / a, 1.0 / 2.4) - b;
}
static float transfer_function_eval_inverse_eotf(
enum wlr_color_transfer_function tf, float x) {
switch (tf) {
case WLR_COLOR_TRANSFER_FUNCTION_SRGB:
return srgb_eval_inverse_eotf(x);
case WLR_COLOR_TRANSFER_FUNCTION_ST2084_PQ:
return st2084_pq_eval_inverse_eotf(x);
case WLR_COLOR_TRANSFER_FUNCTION_EXT_LINEAR:
return x;
case WLR_COLOR_TRANSFER_FUNCTION_GAMMA22:
return powf(x, 1.0 / 2.2);
case WLR_COLOR_TRANSFER_FUNCTION_BT1886:
return bt1886_eval_inverse_eotf(x);
}
abort(); // unreachable
}
static void color_transform_inverse_eotf_eval(
struct wlr_color_transform_inverse_eotf *tr,
float out[static 3], const float in[static 3]) {
for (size_t i = 0; i < 3; i++) {
out[i] = transfer_function_eval_inverse_eotf(tr->tf, in[i]);
}
}
static float lut_1d_get(const uint16_t *lut, size_t len, size_t i) {
if (i >= len) {
i = len - 1;
@ -125,13 +184,28 @@ static float lut_1d_eval(const uint16_t *lut, size_t len, float x) {
return a * (1 - frac_part) + b * frac_part;
}
void color_transform_lut_3x1d_eval(struct wlr_color_transform_lut_3x1d *tr,
static void color_transform_lut_3x1d_eval(struct wlr_color_transform_lut_3x1d *tr,
float out[static 3], const float in[static 3]) {
for (size_t i = 0; i < 3; i++) {
out[i] = lut_1d_eval(&tr->lut_3x1d[tr->dim * i], tr->dim, in[i]);
}
}
void wlr_color_transform_eval(struct wlr_color_transform *tr,
float out[static 3], const float in[static 3]) {
switch (tr->type) {
case COLOR_TRANSFORM_INVERSE_EOTF:
color_transform_inverse_eotf_eval(wlr_color_transform_inverse_eotf_from_base(tr), out, in);
break;
case COLOR_TRANSFORM_LCMS2:
color_transform_lcms2_eval(color_transform_lcms2_from_base(tr), out, in);
break;
case COLOR_TRANSFORM_LUT_3X1D:
color_transform_lut_3x1d_eval(color_transform_lut_3x1d_from_base(tr), out, in);
break;
}
}
void wlr_color_primaries_from_named(struct wlr_color_primaries *out,
enum wlr_color_named_primaries named) {
switch (named) {