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unGamma8() accuracy improvement

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based on upstream changes by @DedeHai
This commit is contained in:
Frank
2025-11-05 22:01:07 +01:00
parent 5122a80f50
commit a956b22a16
1 changed files with 11 additions and 6 deletions
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17
wled00/colors.cpp
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@@ -441,19 +441,20 @@ static void calcInvGammaTable(float gamma)
{
float gammaInv = 1.0f / 2.4f; // surprise surprise: WLED palettes use a fixed gamma of 2.4 !!!
//float gammaInv = 1.0f / gamma; // if we go by the book, 1.0/gamma will revert gamma corrections
for (size_t i = 0; i < 256; i++) {
gammaTinv[i] = (int)(powf((float)i / 255.0f, gammaInv) * 255.0f + 0.5f);
for (size_t i = 1; i < 256; i++) {
gammaTinv[i] = (int)(powf(((float)i - 0.5f) / 255.0f, gammaInv) * 255.0f + 0.5f); // improved by @dedehai
}
gammaTinv[0]=0;
gammaTinv[255]=255;
}
uint8_t __attribute__((hot)) unGamma8(uint8_t value) {
IRAM_ATTR_YN uint8_t __attribute__((hot)) unGamma8(uint8_t value) {
//if (!gammaCorrectCol || (value == 0) || (value == 255)) return value;
if ((value == 0) || (value == 255)) return value;
if ((gammaCorrectVal < 0.999f) || (gammaCorrectVal > 3.0f)) return value;
if (gammaTinv[255] == 0) calcInvGammaTable(gammaCorrectVal);
return gammaTinv[value];
}
uint32_t __attribute__((hot)) unGamma24(uint32_t c) {
IRAM_ATTR_YN uint32_t __attribute__((hot)) unGamma24(uint32_t c) {
if ((gammaCorrectVal < 0.999f) || (gammaCorrectVal > 3.0f)) return c;
if (gammaTinv[255] == 0) calcInvGammaTable(gammaCorrectVal);
return RGBW32(gammaTinv[R(c)], gammaTinv[G(c)], gammaTinv[B(c)], W(c));
@@ -462,6 +463,8 @@ uint32_t __attribute__((hot)) unGamma24(uint32_t c) {
uint8_t gamma8_cal(uint8_t b, float gamma)
{
if (b==0) return 0;
if (b==255) return 255;
return (int)(powf((float)b / 255.0f, gamma) * 255.0f + 0.5f);
}
@@ -469,9 +472,11 @@ uint8_t gamma8_cal(uint8_t b, float gamma)
void calcGammaTable(float gamma)
{
#if !defined(WLED_USE_CIE_BRIGHTNESS_TABLE) // WLEDMM not possible when using the CIE table
for (uint16_t i = 0; i < 256; i++) {
for (uint16_t i = 1; i < 256; i++) {
gammaT[i] = gamma8_cal(i, gamma);
}
gammaT[0]=0;
gammaT[255]=255;
#endif
calcInvGammaTable(gamma); // WLEDMM
}