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This chapter introduces a number of algorithms that are characterized by changing the value of each pixel in an image completely independent on the values of the surrounding pixels. The key concept in this regards is gray-level mapping. First linear gray-level mapping is discussed and exemplified by changing the brightness and contrast in images. Next non-linear gray-level mapping is covered. Hereafter the chapter turns to one of the fundamental concepts within image processing, namely the image histogram. This is then combined with gray-level resulting in methods for improving the image quality and methods for binarising the image by the use of a threshold approach. Due to the importance of the thresholding approach it is discussed in details and different approaches are presented. The chapter finally presents how to combine two images through logic or arithmetic.