__kernel void diff_generator(__global unsigned char *image_a,
    __global unsigned char *image_b, __global unsigned short *image_c, unsigned int range, unsigned int rangeMax)
{
    size_t gx = get_global_id(0);
    size_t offset = range % rangeMax;
    if (offset % gx != 0) return;

    size_t px32bit = gx * 4;
    size_t px565 = gx;

    if (image_a[px32bit] == image_b[px32bit]) return;

    image_a[px32bit] = image_b[px32bit];
    image_c[px565] = ((image_b[px32bit+2] & 0b11111000) << 8) | ((image_b[px32bit + 1] & 0b11111100) << 3) | (image_b[px32bit + 0] >> 3);
}