precision highp float; varying vec2 vVertexPosition; uniform highp float uWidth; uniform highp float uHeight; highp int GetPixelNum (highp float position, highp float size) { return int (floor (((position + 1.0) * size / 2.0))); } void main (void) { highp int a = GetPixelNum (vVertexPosition.x, uWidth); highp int b = GetPixelNum (vVertexPosition.y, uHeight); gl_FragColor = vec4 (float (a) / 255.0, float (b) / 255.0, 0.0, 1.0); }