Here I am going to share one of the simplest approach to apply blur. This is not an optimized solution. For an optimized solution you can go for multi-pass rendering and (or) down sampling.

In this approach bluring will be done by taking average color value around a rectangular are of the pixel. Most of this operation will be performed in the fragment shader. This is a single pass algorithm.

In this approach bluring will be done by taking average color value around a rectangular are of the pixel. Most of this operation will be performed in the fragment shader. This is a single pass algorithm.

### Vertex Shader

As we are doing most of the operation in the fragment shader, vertex shader will be very straight forward.

// Vertex coordinate attribute vec4 aPosition; // Texture coordinate attribute vec2 aTexCoordinate; // Texture coordinate to be passed to fragment shader varying vec2 vTexCoordinate; void main() { vTexCoordinate = aTexCoordinate; gl_Position = aPosition; }

### Fragment Shader

precision mediump float; // The sampler object uniform sampler2D uSampler; // Texture coordinate passed from vertex shader varying vec2 vTexCoordinate; // This is the value that needs to be added(subtracted) to a // texture point to get the next(previous) pixel in the X direction // This value can be calculated as 1/texturewidth uniform float uXPixelDistance; // This is the value that needs to be added(subtracted) to a // texture point to get the next(previous) pixel in the Y direction // This value can be calculated as 1/textureheight uniform float uYPixelDistance; // How to jump to next pixel, 1 means the very next pixel, // 2 means the 2th pixel, and so on. const float jump = 2.0f; // Number of points around the current point const float pointRange = 10.0f; void main() { vec4 color = vec4(0, 0, 0, 0); vec2 point; int count = 0; // Calculate the total color intensity around the pixel // In this case we are calculating pixel intensity around 10 pixels for(float u = -pointRange; u < pointRange ; u+=jump) { for(float v = -pointRange ; v < pointRange ; v+=jump) { point.x = vTexCoordinate.x + u * uXPixelDistance; point.y = vTexCoordinate.y + v * uYPixelDistance; // If the point is within the range[0, 1] if (point.y >= 0.0f && point.x >= 0.0f && point.y <= 1.0f && point.x <= 1.0f ) { ++count; color += texture2D(uSampler, point.xy); } } } // Take the average intensity for the region color = color / float(count); gl_FragColor = vec4(color.xyz, 1.0f); }

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