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November 28, 2023 09:12
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Dart ITU-R BT.2446 Conversion Method C, From HDR Toys glsl
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| // --------------------------------------------------------------------------------------------------------------------------------------- | |
| // ITU-R BT.2446 Conversion Method C | |
| // https://www.itu.int/pub/R-REP-BT.2446 | |
| //!HOOK OUTPUT | |
| //!BIND HOOKED | |
| //!DESC tone mapping (bt.2446c) | |
| Vector3 RGB_to_XYZ(Vector3 RGB) { | |
| Matrix3 M = Matrix3( | |
| 0.6369580483012914, | |
| 0.14461690358620832, | |
| 0.1688809751641721, | |
| 0.2627002120112671, | |
| 0.6779980715188708, | |
| 0.05930171646986196, | |
| 0.000000000000000, | |
| 0.028072693049087428, | |
| 1.060985057710791); | |
| return RGB..applyMatrix3(M); | |
| } | |
| Vector3 XYZ_to_RGB(Vector3 XYZ) { | |
| Matrix3 M = Matrix3( | |
| 1.716651187971268, | |
| -0.355670783776392, | |
| -0.253366281373660, | |
| -0.666684351832489, | |
| 1.616481236634939, | |
| 0.0157685458139111, | |
| 0.017639857445311, | |
| -0.042770613257809, | |
| 0.942103121235474); | |
| return XYZ..applyMatrix3(M); | |
| } | |
| Vector3 XYZ_to_xyY(Vector3 XYZ) { | |
| double X = XYZ.x; | |
| double Y = XYZ.y; | |
| double Z = XYZ.z; | |
| double divisor = X + Y + Z; | |
| if (divisor == 0.0) divisor = 1e-6; | |
| double x = X / divisor; | |
| double y = Y / divisor; | |
| return Vector3(x, y, Y); | |
| } | |
| Vector3 xyY_to_XYZ(Vector3 xyY) { | |
| double x = xyY.x; | |
| double y = xyY.y; | |
| double Y = xyY.z; | |
| double multiplo = Y / max(y, 1e-6); | |
| double z = 1.0 - x - y; | |
| double X = x * multiplo; | |
| double Z = z * multiplo; | |
| return Vector3(X, Y, Z); | |
| } | |
| const double ip = 0.58535; // linear length | |
| const double k1 = 0.83802; // linear strength | |
| const double k3 = 0.74204; // shoulder strength | |
| double f2(double Y, double k1, double k3, double ip) { | |
| ip /= k1; | |
| double k2 = (k1 * ip) * (1.0 - k3); | |
| double k4 = (k1 * ip) - (k2 * log(1.0 - k3)); | |
| return Y < ip ? Y * k1 : log((Y / ip) - k3) * k2 + k4; | |
| } | |
| double curve2(double x) { | |
| const double over_white = 1019.0 / 940.0; // 109% range (super-whites) | |
| return f2(x, k1, k3, ip) / over_white; | |
| } | |
| Vector4 hook3(double r, double g, double b) { | |
| Vector4 color = Vector4(r, g, b, 1.0); | |
| color.rgb = RGB_to_XYZ(color.rgb); | |
| color.rgb = XYZ_to_xyY(color.rgb); | |
| // color.z = curve2(color.z); | |
| color.rgb = xyY_to_XYZ(color.rgb); | |
| color.rgb = XYZ_to_RGB(color.rgb); | |
| return color; | |
| } | |
| void applyToneMapping2446c(Float32List hdrImage) { | |
| for (int i = 0; i < hdrImage.length; i += 3) { | |
| final color = hook3(hdrImage[i], hdrImage[i + 1], hdrImage[i + 2]); | |
| hdrImage[i] = color.x; | |
| hdrImage[i + 1] = color.y; | |
| hdrImage[i + 2] = color.z; | |
| } | |
| } |
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