slang-shaders/dithering/shaders/gendither.slang

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#version 450
// Gendither
//
// Copyright (C) 2013-2014 leilei
// adapted for slang format by hunterk
//
// This program is free software; you can redistribute it and/or modify it
// under the terms of the GNU General Public License as published by the Free
// Software Foundation; either version 2 of the License, or (at your option)
// any later version.
layout(push_constant) uniform Push
{
vec4 SourceSize;
vec4 OriginalSize;
vec4 OutputSize;
uint FrameCount;
} params;
layout(std140, set = 0, binding = 0) uniform UBO
{
mat4 MVP;
} global;
// This table is a lazy jailbar pattern
int erroredtable[16] = {
0,1,0,1,
16,15,16,15,
0,1,0,1,
16,15,16,15
};
#pragma stage vertex
layout(location = 0) in vec4 Position;
layout(location = 1) in vec2 TexCoord;
layout(location = 0) out vec2 vTexCoord;
void main()
{
gl_Position = global.MVP * Position;
vTexCoord = TexCoord;
}
#pragma stage fragment
layout(location = 0) in vec2 vTexCoord;
layout(location = 0) out vec4 FragColor;
layout(set = 0, binding = 2) uniform sampler2D Source;
void main()
{
vec3 final = texture(Source, vTexCoord).rgb;
vec2 ditheu = vTexCoord.xy * params.SourceSize.xy;
// Dither
int ditdex = int(mod(ditheu.x, 4.0)) * 4 + int(mod(ditheu.y, 4.0)); // 4x4!
ivec3 color;
ivec3 colord;
color.r = int(final.r) * 224;
color.g = int(final.g) * 224;
color.b = int(final.b) * 224;
int yeh = 0;
int ohyes = 0;
// looping through a lookup table matrix
for (yeh=ditdex; yeh<(ditdex+16); yeh++) ohyes = erroredtable[yeh-15];
colord.r = color.r + ohyes;
colord.g = color.g + ohyes;
colord.b = color.b + ohyes;
final.rgb += colord.rgb * 0.003921568627451; // divide by 255, i don't trust em
// Reduce color depth
float why = 1.0;
vec3 reduceme = vec3(1.0);
float radooct = 4.4; // 32 is usually the proper value // 4.4 was eyeballed
reduceme.r = pow(final.r, why);
reduceme.r *= radooct;
reduceme.r = int(floor(reduceme.r));
reduceme.r /= radooct;
reduceme.r = pow(reduceme.r, why);
reduceme.g = pow(final.g, why);
reduceme.g *= radooct;
reduceme.g = int(floor(reduceme.g));
reduceme.g /= radooct;
reduceme.g = pow(reduceme.g, why);
reduceme.b = pow(final.b, why);
reduceme.b *= radooct;
reduceme.b = int(floor(reduceme.b));
reduceme.b /= radooct;
reduceme.b = pow(reduceme.b, why);
// Brightness cap
reduceme.rgb = clamp(reduceme.rgb, vec3(0.0), vec3(0.875));
FragColor = vec4(reduceme.rgb, 1.0);
}