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color-lcms: compare parameters with tolerance

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Comparing floating-point values for identity is fragile. Comparaing with
a small tolerance allows for matches that differ only due to numerical
precision of computations.

The tolerance is taken from
weston_color_tf_info_from_parametric_curve().

Signed-off-by: Pekka Paalanen <pekka.paalanen@collabora.com>
This commit is contained in:
Pekka Paalanen 2025-09-25 16:05:09 +03:00 • committed by Pekka Paalanen
parent d7030571c5
commit be71b5a094
1 changed files with 14 additions and 9 deletions
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23
libweston/color-lcms/color-transform.c
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@ -434,6 +434,11 @@ lcms_curve_matches_any_tf(struct weston_compositor *compositor,
return weston_color_tf_info_from_parametric_curve(&curve);
}
static bool
is_lcms_curve_param_eq(float a, float b)
{
return fabsf(a - b) < 1e-5;
}
static bool
init_curve_from_type_1(struct weston_compositor *compositor,
@ -461,8 +466,8 @@ init_curve_from_type_1(struct weston_compositor *compositor,
/* This is a pure power-law with custom exp. If clamped_input == false
* and all channels behave the same, this matches WESTON_TF_POWER. */
if (!clamped_input &&
type_1_params[0][0] == type_1_params[1][0] &&
type_1_params[0][0] == type_1_params[2][0]) {
is_lcms_curve_param_eq(type_1_params[0][0], type_1_params[1][0]) &&
is_lcms_curve_param_eq(type_1_params[0][0], type_1_params[2][0])) {
tf_info = weston_color_tf_info_from(compositor, WESTON_TF_POWER);
curve->type = WESTON_COLOR_CURVE_TYPE_ENUM;
enumerated->tf = (struct weston_color_tf){
@ -537,9 +542,9 @@ init_curve_from_type_1_inverse(struct weston_compositor *compositor,
* clamped_input == false and all channels behave the same,
* this matches WESTON_TF_POWER. */
if (!clamped_input &&
type_1_params[0][0] == type_1_params[1][0] &&
type_1_params[0][0] == type_1_params[2][0]) {
if (type_1_params[0][0] == 0.0f) {
is_lcms_curve_param_eq(type_1_params[0][0], type_1_params[1][0]) &&
is_lcms_curve_param_eq(type_1_params[0][0], type_1_params[2][0])) {
if (is_lcms_curve_param_eq(type_1_params[0][0], 0.0f)) {
err_msg = "WARNING: xform has a LittleCMS type -1 curve " \
"(inverse of pure power-law) with exponent 1 " \
"divided by 0, which is invalid";
@ -588,7 +593,7 @@ init_curve_from_type_1_inverse(struct weston_compositor *compositor,
for (i = 0; i < 3; i++) {
g = type_1_params[i][0];
if (g == 0.0f) {
if (is_lcms_curve_param_eq(g, 0.0f)) {
err_msg = "WARNING: xform has a LittleCMS type -1 curve " \
"(inverse of pure power-law) with exponent 1 " \
"divided by 0, which is invalid";
@ -777,21 +782,21 @@ init_curve_from_type_4_inverse(struct weston_compositor *compositor,
c = type_4_params[i][3];
d = type_4_params[i][4];
if (g == 0.0f) {
if (is_lcms_curve_param_eq(g, 0.0f)) {
err_msg = "WARNING: xform has a LittleCMS type -4 curve " \
"but the param g of the original type 4 curve " \
"is zero, so the inverse is invalid";
goto err;
}
if (a == 0.0f) {
if (is_lcms_curve_param_eq(a, 0.0f)) {
err_msg = "WARNING: xform has a LittleCMS type -4 curve " \
"but the param a of the original type 4 curve " \
"is zero, so the inverse is invalid";
goto err;
}
if (c == 0.0f) {
if (is_lcms_curve_param_eq(c, 0.0f)) {
err_msg = "WARNING: xform has a LittleCMS type -4 curve " \
"but the param c of the original type 4 curve " \
"is zero, so the inverse is invalid";