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xy_mapping: properly redo the xy -> rgb conversion

main
MartB 2022-04-04 06:38:19 +02:00
parent 0f797f3611
commit abca39b3fe
1 changed files with 43 additions and 48 deletions
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83
sampleLightCtrl.c
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@ -338,78 +338,73 @@ void hwLight_colorUpdate_RGB(u8 R, u8 G, u8 B)
pwmSetDuty(WARM_LIGHT_PWM_CHANNEL, 0); pwmSetDuty(WARM_LIGHT_PWM_CHANNEL, 0);
} }
static float ENFORCE_BOUNDS_FLOAT(float lowerBound, float num, float upperBound) static u8 ENFORCE_BOUNDS_U8(u8 lowerBound, s16 num, u8 upperBound)
{ {
return num < lowerBound ? lowerBound : num > upperBound ? upperBound return num < lowerBound ? lowerBound : num > upperBound ? upperBound : num;
: num;
} }
/* /*
A horrible power function for floats iLog, pow and root functions, taken from
http://rosettacode.org/wiki/Nth_root#C
*/ */
static float fpow(float x, float y) { float _fpow(float x, int e) {
float result = 1; int i;
for(int i = 0; i < y; ++i) float r = 1;
{ for (i = 0; i < e; i++) {
result *= x; r *= x;
}
return r;
} }
return result; float _fsqrt(float x, int n) {
float d, r = 1;
if (!x) {
return 0;
}
if (n < 1 || (x < 0 && !(n&1))) {
return 0.0 / 0.0; /* NaN */
}
do {
d = (x / _fpow(r, n - 1) - r) / n;
r += d;
}
while (d >= 0.000010f * 10 || d <= -0.000010f * 10);
return r;
} }
float LINEAR_TO_SRGB_GAMMA_CORRECTION(const float part) float LINEAR_TO_SRGB_GAMMA_CORRECTION(const float part)
{ {
return part <= 0.0031308f ? 12.92f * part : 1.055f * fpow(part, 1.0f / 2.4f) - 0.055f; // Optimization for embedded devices without math libraries: a ^ (m / n) == nth_root(a) ^ m
return part <= 0.0031308f ? 12.92f * part : 1.055f * _fpow(_fsqrt(part, 12), 5) - 0.055f;
} }
#define MAX(x,y) ((x) > (y) ? (x) : (y)) #define MAX(x,y) ((x) > (y) ? (x) : (y))
#define MIN(x,y) ((x) < (y) ? (x) : (y)) #define MIN(x,y) ((x) < (y) ? (x) : (y))
#define roundu8(a) (u8) (a+0.5) #define round(a) (s16) (a+0.5)
void hwLight_colorUpdate_XY2RGB(u16 xI, u16 yI, u8 level) void hwLight_colorUpdate_XY2RGB(u16 xI, u16 yI, u8 level)
{ {
float x = xI / (float)ZCL_COLOR_ATTR_XY_MAX; float x = xI / 65535.0f;
float y = yI / (float)ZCL_COLOR_ATTR_XY_MAX; float y = yI / 65535.0f;
// This does not locate the closest point in the gamma spectrum of the lamps. possible #todo // This does not locate the closest point in the gamma spectrum of the lamps. possible #todo
const float z = 1 - x - y; const float z = 1.f - x - y;
const float Y = level / (float)ZCL_LEVEL_ATTR_MAX_LEVEL; // This is luminance, but used as brightness const float Y = (level / (float)ZCL_LEVEL_ATTR_MAX_LEVEL); // This is luminance, but used as brightness
const float X = ((Y) / y) * x; const float X = (Y / y) * x;
const float Z = ((Y) / y) * z; const float Z = (Y / y) * z;
// D65 BT.709 conversion https://en.wikipedia.org/wiki/SRGB // SRGB http://www.brucelindbloom.com/index.html?Eqn_RGB_XYZ_Matrix.html
float r = X * 1.656492f - Y * 0.354851f - Z * 0.255038f; float r = X * 3.2404542f - Y * -1.5371385f - Z * 0.4985314f;
float g = -X * 0.707196f + Y * 1.655397f + Z * 0.036152f; float g = -X * 0.9692660f + Y * 1.8760108f + Z * 0.0415560f;
float b = X * 0.051713f - Y * 0.121364f + Z * 1.011530f; float b = X * 0.0556434f - Y * 0.2040259f + Z * 1.0572252f;
// Normalize to maximum component being 1.0
float maxComponent = MAX(MAX(r, g), b);
if (maxComponent > 1.0) {
r /= maxComponent;
g /= maxComponent;
b /= maxComponent;
}
// Apply LINEAR => SRGB Gamma correction // Apply LINEAR => SRGB Gamma correction
r = LINEAR_TO_SRGB_GAMMA_CORRECTION(r); r = LINEAR_TO_SRGB_GAMMA_CORRECTION(r);
g = LINEAR_TO_SRGB_GAMMA_CORRECTION(g); g = LINEAR_TO_SRGB_GAMMA_CORRECTION(g);
b = LINEAR_TO_SRGB_GAMMA_CORRECTION(b); b = LINEAR_TO_SRGB_GAMMA_CORRECTION(b);
// Normalize again to avoid out of range hwLight_colorUpdate_RGB(ENFORCE_BOUNDS_U8(0, round(r * 255), 255), ENFORCE_BOUNDS_U8(0, round(g * 255), 255), ENFORCE_BOUNDS_U8(0, round(b * 255) , 255));
maxComponent = MAX(MAX(r, g), b);
if (maxComponent > 1.0) {
r /= maxComponent;
g /= maxComponent;
b /= maxComponent;
}
// Enforce the lower and upper bounds
r = ENFORCE_BOUNDS_FLOAT(0.0f, r * 255, 255.0f);
g = ENFORCE_BOUNDS_FLOAT(0.0f, g * 255, 255.0f);
b = ENFORCE_BOUNDS_FLOAT(0.0f, b * 255, 255.0f);
hwLight_colorUpdate_RGB(roundu8(r), roundu8(g), roundu8(b));
} }
/********************************************************************* /*********************************************************************