Function changeContrast

examples/image_processing/image_editing.cpp:20–23

* contrast value should be in the rnage [-1,1] * */

 * contrast value should be in the rnage [-1,1]
 * */
array changeContrast(const array &in, const float contrast) {
    float scale = tan((contrast + 1) * Pi / 4);
    return (((in / 255.0f - 0.5f) * scale + 0.5f) * 255.0f);
}

/**
 * brightness value should be in the rnage [0,1]