Implementing Vignetting in OpenCV

Now that you know about the type of changes that a Vignette mask brings about in images, we can start to think about devising a strategy for the same and ultimately go about implementing the Vignetting operation. As we have discussed, the Vignette mask leaves the central portion of an image bright and darkens the borders in all directions as we move out of the center. Now, the input image (grayscale) that we will be dealing with will have a fixed intensity value for every pixel. What we essentially need to do is modify the value of every pixel in such a manner that the pixels in the center remain at their original intensity levels while the surrounding pixels get progressively darker as we approach the borders.

How can we bring about such a transformation? Well, one way to do that would be to multiply each pixel value with a scaling constant between 0 and 1. The pixels whose intensities need to be kept as is (the ones near the center of the image) should...