What is masking (mask) in an image

In image processing, the word mask is often encountered. So what does this word mean? Here's a quick explanation. 1. What is masking

First of all, we look at what is the process of mask from a physical point of view.
In semiconductor manufacturing, many chip process steps use lithography, a graphic "negative" for these steps called a mask (also known as a "mask"), which is used to cover an opaque graphic template in a selected area of the wafer, and the following corrosion or diffusion will only affect areas outside the selected area.
Image masks are similar in that they use selected images, graphics, or objects to mask the processed images (all or part) to control the area or process of image processing. 2. Use of Masks

2.1 Extract the area of interest: Using pre-made area of interest mask and the image to be processed, to get the image of the area of interest, the image value in the area of interest remains unchanged, and the image value of the region is 0;
2.2 Shielding Effect: Mask the image on some areas of the screen, so that it does not participate in processing or not participate in the calculation of processing parameters, or only the shielding area for processing or statistics;
2.3 Structural feature Extraction: the similarity variable or image matching method is used to detect and extract the structure characteristics similar to the mask in the image.
2.4 Production of special shape images. 3. A small example of masking operations

Take graphs and masks and operations as an example:
Each pixel in the original image and each corresponding pixel in the mask are performed with the operation. such as 1 & 1 = 1;1 & 0 = 0;
For example, a 3 * 3 image with 3 * 3 of the Mask to operate, the resulting image is:
4. Summary

1. In the image, a variety of bit operations, such as and, or, non-operation and ordinary bit operation is similar.
2. If summed up in a sentence, the mask is the operation of various bits between the two images.