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// Based on http://kodemongki.blogspot.com/2011/06/kameraku-custom-shader-effects-example.html

uniform float dividerValue;
const float step_w = 0.0015625;
const float step_h = 0.0027778;

uniform sampler2D source;
uniform lowp float qt_Opacity;
varying vec2 qt_TexCoord0;

void main()
{
    vec2 uv = qt_TexCoord0.xy;
    vec3 t1 = texture2D(source, vec2(uv.x - step_w, uv.y - step_h)).rgb;
    vec3 t2 = texture2D(source, vec2(uv.x, uv.y - step_h)).rgb;
    vec3 t3 = texture2D(source, vec2(uv.x + step_w, uv.y - step_h)).rgb;
    vec3 t4 = texture2D(source, vec2(uv.x - step_w, uv.y)).rgb;
    vec3 t5 = texture2D(source, uv).rgb;
    vec3 t6 = texture2D(source, vec2(uv.x + step_w, uv.y)).rgb;
    vec3 t7 = texture2D(source, vec2(uv.x - step_w, uv.y + step_h)).rgb;
    vec3 t8 = texture2D(source, vec2(uv.x, uv.y + step_h)).rgb;
    vec3 t9 = texture2D(source, vec2(uv.x + step_w, uv.y + step_h)).rgb;
    vec3 xx = t1 + 2.0*t2 + t3 - t7 - 2.0*t8 - t9;
    vec3 yy = t1 - t3 + 2.0*t4 - 2.0*t6 + t7 - t9;
    vec3 rr = sqrt(xx * xx + yy * yy);
    vec3 col = rr * 2.0 * t5;
    if (uv.x < dividerValue)
        gl_FragColor = qt_Opacity * vec4(col, 1.0);
    else
        gl_FragColor = qt_Opacity * texture2D(source, uv);
}