Palette Shader Quick Fix

testPos = vec2(corner.x + u_pixelSize.x * floor(u_paletteId + 1.0), i);
return mix(texture2D(u_palTexture, vec2(testPos.x - u_pixelSize.x, testPos.y)), texture2D(u_palTexture, testPos), fract(u_paletteId));