A fragment shader for glsl v1.0 that create a pixellation effect.

fs_pixellation.glsl

#version 100

precision mediump float;

uniform sampler2D u_texId;
// render target width
uniform float u_rt_w;
// render target height
uniform float u_rt_h;
// width of a low resolution pixel
uniform float u_pixel_w;
// height of a low resolution pixel
uniform float u_pixel_h;
varying vec2 vTexCoords;


void main(){
    float dx = u_pixel_w*(1.0/u_rt_w);
    float dy = u_pixel_h*(1.0/u_rt_h);
    vec2 coord = vec2(dx*floor(vTexCoords.x/dx), dy*floor(vTexCoords.y/dy));
    vec3 tc = texture2D(u_texId, coord).rgb;
    gl_FragColor = vec4(tc, 1.0);
}