diff options
Diffstat (limited to 'system/shaders/yuv2rgb_basic.glsl')
| -rw-r--r-- | system/shaders/yuv2rgb_basic.glsl | 5 |
1 files changed, 4 insertions, 1 deletions
diff --git a/system/shaders/yuv2rgb_basic.glsl b/system/shaders/yuv2rgb_basic.glsl index 6841d5f0f8..1527a7a4d1 100644 --- a/system/shaders/yuv2rgb_basic.glsl +++ b/system/shaders/yuv2rgb_basic.glsl @@ -19,8 +19,11 @@ uniform float m_stretch; #define POSITION(pos) stretch(pos) vec2 stretch(vec2 pos) { + // our transform should map [0..1] to itself, with f(0) = 0, f(1) = 1, f(0.5) = 0.5, and f'(0.5) = b. + // a simple curve to do this is g(x) = b(x-0.5) + (1-b)2^(n-1)(x-0.5)^n + 0.5 + // where the power preserves sign. n = 2 is the simplest non-linear case (required when b != 1) float x = pos.x - 0.5; - return vec2(mix(x, x * abs(x) * 2.0, m_stretch) + 0.5, pos.y); + return vec2(mix(2.0 * x * abs(x), x, m_stretch) + 0.5, pos.y); } #else #define POSITION(pos) (pos) |