IS = `#version 300 es
        precision highp float;

        #define PIXEL_AT(_x, _y) (texture(u_image, v_texCoord + onePixel * vec2(_x, _y)))
        #define g1 0.25
        #define g2 0.125
        #define g3 0.0625

        uniform sampler2D u_image;
        uniform vec2 u_dimensions;
        uniform float u_threshold;
        uniform float u_k;
        uniform int u_step;

        in vec2 v_texCoord;
        out vec4 out_color;

        float Harris(float Ixx, float Iyy, float Ixy, float k, float thres