Configurable Box Blur

I could not find a good blur shader and just ended with learning the shader language. I used the post from Schorsch as a template He linked to a created shadertoy by him; so it might be that the license has to be changed?

I’m not very familiar with the shading language but I thought I read that GLES2 does not support for loops. So I gues this will work in Vulkan and GLES3.

Do note that this shader also blurs the alpha channel; something that is easily changed.

Bugfix, edge blur was incorrect. Looked at Exuin’s Blur.

Shader code
shader_type canvas_item;

uniform int strength: hint_range(1, 512) = 2;

vec4 blur_size(sampler2D tex,vec2 fragCoord, vec2 pixelSize) {
    vec4 color = vec4(0.,0.,0.,0.);
    float strengthFloat = float(strength);	

    vec2 pixel = fragCoord/pixelSize;
    int x_min = max(int(pixel.x-strengthFloat), 0);
    int x_max = min(int(pixel.x+strengthFloat), int(1./pixelSize.x));
    int y_min = max(int(pixel.y-strengthFloat), 0);
    int y_max = min(int(pixel.y+strengthFloat), int(1./pixelSize.y));

    int count =0;

    // Sum the pixels colors
    for(int x=x_min; x <= x_max; x++) {
        for(int y = y_min; y <= y_max; y++) {           
            color += texture(tex, vec2(float(x), float(y)) * pixelSize);
    // Divide the color by the number of colors you summed up
    color /= float(count);
    return color;

void fragment() {	
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Related shaders

Box Blur

Artsy Circle blur type thingy

Gaussian Blur


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