uniform float scale_factor;
uniform sampler2D tex;
in vec2 pass_TexCoord;
void main()
{
    float scan_color = 2.0 * abs(mod((gl_FragCoord.y + 0.5) / scale_factor * 2.0, 2.0) - 1.0);
    vec3 pixel = texture2D(tex, pass_TexCoord).rgb;
    pixel = (pixel - 0.5) * 1.035 + 0.5;
    pixel = pixel * (pixel + (scan_color * (1.0 - pixel)));
    pixel = (pixel + 0.5) * 1.035 - 0.5;
    gl_FragColor = vec4(pixel, texture2D(tex, pass_TexCoord).a);
};