slang-shaders/nes_raw_palette/shaders/cgwg-famicom-geom/lowpass-chroma.slang

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#version 450
layout(push_constant) uniform Push
{
vec4 SourceSize;
vec4 OriginalSize;
vec4 OutputSize;
uint FrameCount;
float postfilter_taps, postfilter_chromacutoff;
} params;
// after mixing with the adaptive comb filter
#pragma parameter postfilter_taps "Post-filter Taps" 15.0 1.0 30.0 1.0
#define postfiltertaps int(params.postfilter_taps)
#pragma parameter postfilter_chromacutoff "Post-filter Chroma Cutoff" 0.3 0.1 1.0 0.05
#define postfilterchromacutoff params.postfilter_chromacutoff
layout(std140, set = 0, binding = 0) uniform UBO
{
mat4 MVP;
} global;
#pragma stage vertex
layout(location = 0) in vec4 Position;
layout(location = 1) in vec2 TexCoord;
layout(location = 0) out vec2 texCoord;
void main()
{
gl_Position = global.MVP * Position;
texCoord = TexCoord;
}
#pragma stage fragment
layout(location = 0) in vec2 texCoord;
layout(location = 0) out vec4 FragColor;
layout(set = 0, binding = 2) uniform sampler2D Source;
vec3 chroma_sample(vec2 shift) {
vec2 coord = texCoord + params.SourceSize.zw*shift;
if (coord.x < 0.0 || coord.x > 1.0) return vec3(0.0);
return texture(Source, texCoord + params.SourceSize.zw*shift).xyz-vec3(0,0.5,0.5);
}
float sinc(float x) {
x = max(abs(x),0.0001);
return sin(x)/x;
}
void main()
{
const int width = postfiltertaps;
const float bw_c = postfilterchromacutoff/3.0;
const vec4 one = vec4(1.0);
const float PI = 3.14159265359;
const vec4 PI_6 = vec4(PI/6.0);
float norm_c = 0.0;
vec3 yiq = vec3(0.0);
yiq.x = chroma_sample(vec2(0,0)).x;
for (int i = -width/2; i <= width/2; i++) {
// Hamming window
const float alpha = 0.54;
const float beta = 0.46;
float window = alpha - beta * cos(2.0*PI/(width-1)*(width/2+i));
float chromafilt = 2.0*bw_c*sinc(2.0*PI*bw_c*i);
vec3 samp = chroma_sample(vec2(i,0));
float filt = window*chromafilt;
yiq.yz += samp.yz*vec2(filt);
norm_c += filt;
}
yiq *= vec3(1.0, 1.0/norm_c, 1.0/norm_c);
FragColor = vec4(dot(yiq, vec3(1.0, 0.946882, 0.623557)),
dot(yiq, vec3(1.0,-0.274788,-0.635691)),
dot(yiq, vec3(1.0,-1.108545, 1.709007)),
0.0);
}