How do I normalize an image?

Question

If I have a series of pixels, which range from say -500 to +1000, how would I normalize all the pixels on the same gradient so that they fall between a specific range, say 0

Answer 1

Create two variables, MinInputValue and MaxInputValue. Initialize MinInputValue to a very large positive number (higher than the largest pixel value you ever expect to see) and MaxInputValue to a very large negative number (lower than the lowest pixel value you ever expect to see).

Loop over every pixel in the image. For each pixel, if the pixel value PixelValue is lower than MinInputValue, set MinInputValue to PixelValue. If the pixel value is higher than MaxInputValue, set MaxInputValue to PixelValue.

Create a new variable, InputValueRange, and set it to MaxInputValue - MinInputValue.

Once this is done, loop over every pixel in the image again. For each pixel PixelValue, calculate the output pixel value as 255.0 * (PixelValue - MinInputValue) / InputValueRange. You can assign this new value back to the original PixelValue, or you can set the corresponding pixel in an output image of the same size.