slang-shaders/retro/shaders/pixellate.slang

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#version 450
layout(std140, set = 0, binding = 0) uniform UBO
{
mat4 MVP;
vec4 OutputSize;
vec4 OriginalSize;
vec4 SourceSize;
} global;
#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()
{
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vec2 texelSize = global.SourceSize.zw;
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vec2 range = vec2(abs(global.SourceSize.x / (global.OutputSize.x * global.SourceSize.x)), abs(global.SourceSize.y / (global.OutputSize.y * global.SourceSize.y)));
range = range / 2.0 * 0.999;
float left = vTexCoord.x - range.x;
float top = vTexCoord.y + range.y;
float right = vTexCoord.x + range.x;
float bottom = vTexCoord.y - range.y;
vec3 topLeftColor = texture(Source, (floor(vec2(left, top) / texelSize) + 0.5) * texelSize).rgb;
vec3 bottomRightColor = texture(Source, (floor(vec2(right, bottom) / texelSize) + 0.5) * texelSize).rgb;
vec3 bottomLeftColor = texture(Source, (floor(vec2(left, bottom) / texelSize) + 0.5) * texelSize).rgb;
vec3 topRightColor = texture(Source, (floor(vec2(right, top) / texelSize) + 0.5) * texelSize).rgb;
vec2 border = clamp(round(vTexCoord / texelSize) * texelSize, vec2(left, bottom), vec2(right, top));
float totalArea = 4.0 * range.x * range.y;
vec3 averageColor;
averageColor = ((border.x - left) * (top - border.y) / totalArea) * topLeftColor;
averageColor += ((right - border.x) * (border.y - bottom) / totalArea) * bottomRightColor;
averageColor += ((border.x - left) * (border.y - bottom) / totalArea) * bottomLeftColor;
averageColor += ((right - border.x) * (top - border.y) / totalArea) * topRightColor;
FragColor = vec4(averageColor, 1.0);
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}