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Unsharp masking (USM) is an image sharpening technique, first implemented in darkroom photography, but now commonly used in digital image processing software. Its name derives from the fact that the technique uses a blurred , or "unsharp", negative image to create a mask of the original image.
Edge enhancement is an image processing filter that enhances the edge contrast of an image or video in an attempt to improve its acutance (apparent sharpness).. The filter works by identifying sharp edge boundaries in the image, such as the edge between a subject and a background of a contrasting color, and increasing the image contrast in the area immediately around the edge.
In image processing, a kernel, convolution matrix, or mask is a small matrix used for blurring, sharpening, embossing, edge detection, and more. This is accomplished by doing a convolution between the kernel and an image. Or more simply, when each pixel in the output image is a function of the nearby pixels (including itself) in the input image ...
In digital photography, onboard camera software and image postprocessing tools such as Photoshop or GIMP offer various sharpening facilities, the most widely used of which is known as "unsharp mask" because the algorithm is derived from the eponymous analog processing method. In the example image, two light gray lines were drawn on a gray ...
Overshoot (bottom of image), caused by using unsharp masking to sharpen an image The sine integral, which is the step response of an ideal low-pass filter. The sinc function, which is the impulse response of an ideal low-pass filter.
Graphics programs can be used to both sharpen and blur images in a number of ways, such as unsharp masking or deconvolution. [16] Portraits often appear more pleasing when selectively softened (particularly the skin and the background) to better make the subject stand out.
An image of the Notre Dame cathedral as seen from the Eiffel Tower The same image, with added global contrast, and local contrast increased through unsharp masking. There are many possible definitions of contrast. Some include color; others do not.
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