Several methods of image sharpening

There are two methods, USM filter processing image and SmartSharpen filter.

Smoothing usually blurs the boundaries and contours in an image. In order to reduce this adverse effect, it is necessary to use image sharpening technology to make the edge of the image clear.

In the process of underwater image enhancement, in addition to denoising and expanding contrast, it is sometimes necessary to strengthen the edge and outline of the scene in the image. The edge and contour are often located in the place where the gray level changes suddenly, so we can intuitively think of using the gray level difference to extract the edge and contour.

Extended data:

The essence of sharpening operation is to increase the contrast of image details, which is helpful for our eyes to see the image details clearly, so that the image appears angular and clear, which is a necessary condition for all good quality photographic works.

The image directly copied by the scanner will look monotonous and fuzzy if it is not cropped, so we often need to sharpen the processed image.

Threshold setting is a key parameter to avoid problems such as spots and pits caused by sharpening. After the correct setting, the image can not only maintain the perfection of smooth natural tones (such as pure blue sky in the background), but also emphasize the contrast of changing details.

In general prepress processing, the value is 3 to 4, which should not exceed 10, which will reduce the sharpening effect and make the image look ugly.

Baidu encyclopedia-image sharpening