2.2 Pixel Operations
- Thresholding -
change to zero if pixel value beyond one or more threshold value(s)
- Adaptive Thresholding - thresholding using local values near pixel
- Contrast and Brightness Stretching - uses linear functions to
generate histogram (or brightness-contrast) transform, see:
1.3.3.1 to
1.3.3.5
- Histogram Equalization - uses non linear functions to generate histogram (or brightness-contrast) transform
- reduce contrast of brighter regions: log, root, etc.
A common use for the log transform is for viewing Fourier
transformed images where the brightest pixel is 10 time brighter than the
second brightest pixel. Another common use is when the main focus in an
image is relatively dark and the background is relatively bright.
- increase contrast of brighter regions: exp, power, etc.
- middle region changes: use arbitrary monotonic functions or use non monotonic
functions and generate cummulative histogram
- Invert -
Each pixel value is subtracted from the maximum pixel value.
For greyscale images this reverses light and dark. For color images this changes to
color negative.
