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#version 330 core
in vec2 TexCoords;
uniform sampler2D TexId;
out vec4 FragColor;
vec4 filter_color_invert(vec4 color)
{
vec4 res = vec4(vec3(1.0) - vec3(color), 1.0);
return res;
}
vec4 filter_color_grayscale(vec4 color)
{
// we will need to average the colors
// float average = (color.x + color.y + color.z) / 3.0f;
// in reality, human our most sensitive towards green and least to blue, so will need to weight those
float average = 0.2126 * color.r + 0.7152 * color.g + 0.0722 * color.b;
vec4 res = vec4(vec3(average), 1.0);
return res;
}
// @note: different kernels for experimentation
const float kernel_sharpen[9] = float[](
-1, -1, -1,
-1, 9, -1,
-1, -1, -1
);
const float kernel_blur[9] = float[](
1.0/16.0, 2.0/16.0, 1.0/16.0,
2.0/16.0, 4.0/16.0, 2.0/16.0,
1.0/16.0, 2.0/16.0, 1.0/16.0
);
const float kernel_edge_detection[9] = float[](
1, 1, 1,
1, -8, 1,
1, 1, 1
);
vec4 filter_kernal_effects()
{
const float offset = 1.0/300.0;
vec2 offsets[9] = vec2[](
vec2(-offset, offset), // top left
vec2( 0, offset), // top center
vec2( offset, offset), // top right
vec2(-offset, 0), // center left
vec2( 0, 0), // center center
vec2( offset, 0), // center right
vec2(-offset, -offset), // bot left
vec2( 0, -offset), // bot center
vec2( offset, -offset) // bot right
);
float kernal[9] = kernel_edge_detection;
vec3 kernalValue = vec3(0.0);
vec3 sampleTex[9];
for (int i=0; i<9; i++) {
sampleTex[i] = vec3(texture(TexId, TexCoords + offsets[i]));
kernalValue += (kernal[i] * sampleTex[i]);
}
vec4 res = vec4(kernalValue, 1.0);
return res;
}
void main() {
FragColor = filter_kernal_effects();
}
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