Pixelation shader in Ray

pixelation.rb

# Pixelation post-processing effect
# http://www.geeks3d.com/20101029/shader-library-pixelation-post-processing-effect-glsl/

# Shaders -------------------

PIXEL_SHADER =<<END
uniform sampler2D sceneTex; // 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(sceneTex, uv).rgb;
  }
	gl_FragColor = vec4(tc, 1.0);
}
END

# Code ----------------------------

$:.unshift File.expand_path(File.dirname(__FILE__) + "/../../lib")
$:.unshift File.expand_path(File.dirname(__FILE__) + "/../../ext")

require 'ray'

def path_of(res)
  File.expand_path File.join(File.dirname(__FILE__), '../../test/res', res)
end

Ray.game "Pixelization shader" do
  register { add_hook :quit, method(:exit!) }

  scene :pixelization do
    @sprites = []
    @sprites << sprite(path_of("sprite.png"))
    @sprites << sprite(path_of("sprite.png"), at: [400, 200])
    
    window.shader.compile(:frag => StringIO.new(PIXEL_SHADER))
    window.shader[:sceneTex] = 0
    window.shader[:rt_w] = 640
    window.shader[:rt_h] = 480
    window.shader[:vx_offset] = 0.45 # How much of screen to pixelize (0: none, 0.5: left side, 1: all )
    window.shader[:pixel_w] = 1.0 # Width of meta-pixel in pixels.
    window.shader[:pixel_h] = 1.0 # Height of meta-pixel in pixels.
    
    # Animate so that processed pixels grow from 1 to 100 normal pixels.
    @animation = block_animation :duration => 5, :block => proc { |target, progression|
      target[:pixel_w] = progression
      target[:pixel_h] = progression
    }

    @animation.start window.shader

    always do
      @animation.update
    end
    
    render do |win|
      @sprites.each {|s| win.draw s }
    end
  end
  
  scenes << :pixelization
end