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#version 450
layout(local_size_x = 8, local_size_y = 8) in;
layout(binding = 0) uniform sampler2D input_texture;
layout(binding = 1, rgba8) uniform writeonly image2D output_image;
layout(push_constant) uniform PushConstants {
vec2 scale_factor;
vec2 input_size;
} constants;
vec4 cubic(float v) {
vec4 n = vec4(1.0, 2.0, 3.0, 4.0) - v;
vec4 s = n * n * n;
float x = s.x;
float y = s.y - 4.0 * s.x;
float z = s.z - 4.0 * s.y + 6.0 * s.x;
float w = s.w - 4.0 * s.z + 6.0 * s.y - 4.0 * s.x;
return vec4(x, y, z, w) * (1.0/6.0);
}
vec4 bicubic_sample(sampler2D tex, vec2 tex_coord) {
vec2 tex_size = constants.input_size;
vec2 inv_tex_size = 1.0 / tex_size;
tex_coord = tex_coord * tex_size - 0.5;
vec2 fxy = fract(tex_coord);
tex_coord -= fxy;
vec4 xcubic = cubic(fxy.x);
vec4 ycubic = cubic(fxy.y);
vec4 c = tex_coord.xxyy + vec2(-0.5, +1.5).xyxy;
vec4 s = vec4(xcubic.xz + xcubic.yw, ycubic.xz + ycubic.yw);
vec4 offset = c + vec4(xcubic.yw, ycubic.yw) / s;
offset *= inv_tex_size.xxyy;
vec4 sample0 = texture(tex, offset.xz);
vec4 sample1 = texture(tex, offset.yz);
vec4 sample2 = texture(tex, offset.xw);
vec4 sample3 = texture(tex, offset.yw);
float sx = s.x / (s.x + s.y);
float sy = s.z / (s.z + s.w);
return mix(
mix(sample3, sample2, sx),
mix(sample1, sample0, sx),
sy
);
}
void main() {
ivec2 pos = ivec2(gl_GlobalInvocationID.xy);
ivec2 size = imageSize(output_image);
if (pos.x >= size.x || pos.y >= size.y) {
return;
}
vec2 tex_coord = vec2(pos) / vec2(size);
vec4 color = bicubic_sample(input_texture, tex_coord);
imageStore(output_image, pos, color);
}
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