#ifdef GL_ES
precision lowp sampler2DRect;
precision mediump float;

varying vec2 vTexCoord;
vec4 fragColor;
#else
in vec2 vTexCoord;
out vec4 fragColor;
#endif
uniform sampler2DRect incoming;

void main()
{
        vec4 b = texture(incoming, vec2(vTexCoord.s - 1, vTexCoord.t))
		+ texture(incoming, vec2(vTexCoord.s + 1, vTexCoord.t));
        vec4 c = texture(incoming, vTexCoord.st);

        fragColor = max(b * 0.5, c);
#ifdef GL_ES
    gl_FragColor = fragColor;
#endif
}