Chapter 4
Operations in Intensity Space
Wolfgang Birkfellner
4.1 The Intensity Transform Function and The Dynamic Range
We have already seen that not all types of gray values are suitable for direct display. For instance, in the case of the MR or CT images decoded in Example 3.7.2, the easiest way to get a suitable range of gray scales for display is a linear transform of the gray values ρ so that the maximum and the minimum of the image fit with the data range of the pixels to be displayed. If we look at the BRAIN_CT DICOM file, it turns out that the minimum data value of this CT slice is -1057, and the maximum value is 1440, whereas a conventional gray scale image format like PGM usually expects a range ρ ∈ {0 ... 255}; the colormap(gray)
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