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uniform sampler2D tex;
uniform int divider;
uniform float width;
uniform float height;
uniform int downsampling_mode;
uniform float opacity_factor;
#define CORRECTION 2.25
#define SIZE_ADDITION 3.0
vec4 get_texture_at_position(vec2 position) {
vec2 raw_position = position + vec2(CORRECTION, CORRECTION);
vec2 raw_uv = raw_position / vec2(max(1.0, width + SIZE_ADDITION), max(1.0, height + SIZE_ADDITION));
return texture2D(tex, raw_uv);
}
vec2 get_corrected_position() {
vec2 raw_uv = cogl_tex_coord0_in.st;
vec2 raw_position = raw_uv * vec2(width + SIZE_ADDITION, height + SIZE_ADDITION);
return raw_position - vec2(CORRECTION, CORRECTION);
}
void main() {
vec4 source_color = texture2D(tex, cogl_tex_coord0_in.st);
vec4 effect_color = vec4(0.0);
ivec2 corrected_position = ivec2(get_corrected_position());
vec2 multiplied_position = vec2(corrected_position) * float(divider);
if (any(greaterThan(multiplied_position, vec2(width, height)))) {
cogl_color_out = mix(source_color, effect_color, opacity_factor);
return;
}
// mode 0: boxcar downsampling
if (downsampling_mode == 0) {
vec4 color = vec4(0.);
int count = 0;
for (int i = 0; i < divider; i++) {
for (int j = 0; j < divider; j++) {
vec2 lookup_position = multiplied_position + vec2(float(i), float(j));
if (all(greaterThanEqual(lookup_position, vec2(0.0, 0.0))) &&
all(lessThan(lookup_position, vec2(width, height)))) {
color += get_texture_at_position(lookup_position);
count += 1;
}
}
}
effect_color = color / max(1.0, float(count));
} else
// mode 1: triangular downsampling
if (downsampling_mode == 1) {
vec4 color = vec4(0.);
int count = 0;
int force = 1;
for (int i = 0; i < divider; i++) {
for (int j = 0; j < divider; j++) {
vec2 lookup_position = multiplied_position + vec2(float(i), float(j));
if (all(greaterThanEqual(lookup_position, vec2(0.0, 0.0))) &&
all(lessThan(lookup_position, vec2(width, height)))) {
force = 1 + divider - int(abs(float(divider - i - j)));
color += get_texture_at_position(lookup_position) * float(force);
count += force;
}
}
}
effect_color = color / max(1.0, float(count));
} else
// mode 2: Dirac downsampling
if (downsampling_mode == 2) {
vec2 lookup_position = min(multiplied_position + vec2(float(divider)) * 0.5, vec2(width - 1.0, height - 1.0));
effect_color = get_texture_at_position(lookup_position);
}
cogl_color_out = mix(source_color, effect_color, opacity_factor);
}
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