Pixelate GLSL

[HEADER]
    VERSION     01.00.00.00
    DESCRIPTION Post-processing examples
    COPYRIGHT   2013-2014, The Brenwill Workshop Ltd. All rights reserved.
[/HEADER]

// Using a texture attached to a rendering surface
[TEXTURES]
[/TEXTURES]

///////////////////////////////////////////////
// In post-processing, draw a single texture in clip-space.
// after converting the texture to grayscale.
///////////////////////////////////////////////
[EFFECT]
    NAME            Grayscale

    VERTEXSHADER    ClipSpace_vsh
    FRAGMENTSHADER  Grayscale_fsh
[/EFFECT]

///////////////////////////////////////////////
// Draws a single texture in clip-space.
// In clip-space, we need no transform matrices, because all locations
// are taken to be between +/-1.0 in all three dimensions.
///////////////////////////////////////////////
[VERTEXSHADER]
    NAME        ClipSpace_vsh
    FILE        CC3ClipSpaceTexturable.vsh
[/VERTEXSHADER]

///////////////////////////////////////////////
// Draws a single texture as grayscale.
// Grayscale rendering is processed via the ITU-R BT.709 conversion used for
// high-definition television (HDTV) signals. The alpha component is unchanged.
///////////////////////////////////////////////
[FRAGMENTSHADER]
    NAME        Grayscale_fsh

    [GLSL_CODE]

        uniform sampler2D s_cc3Texture; // 0
        uniform float vx_offset;
        uniform float rt_w; // GeeXLab built-in
        uniform float rt_h; // GeeXLab built-in
        uniform float pixel_w; // 15.0
        uniform float pixel_h; // 10.0
        void main()
        {
            vec2 uv = gl_TexCoord[0].xy;

            vec3 tc = vec3(1.0, 0.0, 0.0);
            if (uv.x < (vx_offset-0.005))
             {
                    float dx = pixel_w*(1./rt_w);
                    float dy = pixel_h*(1./rt_h);
                    vec2 coord = vec2(dx*floor(uv.x/dx), dy*floor(uv.y/dy));
                    tc = texture2D(sceneTex, coord).rgb;
             }
            else if (uv.x>=(vx_offset+0.005))
            {
                    tc = texture2D(s_cc3Texture, uv).rgb;
            }
            gl_FragColor = vec4(tc, 1.0);
    }

    [/GLSL_CODE]
[/FRAGMENTSHADER]