 {
            vec2 onePixel = vec2(1.0, 1.0) / u_dimensions;
            float value = texture(u_image, v_texCoord).r;

            value = localMaximum(v_texCoord, onePixel, value, u_radius);

            out_color = vec4(value,value,value,1);
        }`;

    const FRAG_SOURCE_MARKER = `#version 300 es
        precision highp float;

        #define PIXEL_AT(_x, _y) (texture(u_image, v_texCoord + onePixel * vec2(_x, _y)))

        uniform sampler2D u_image;
        uniform vec2 u_dimensions;
        unif