Grey Scale Manipulation

1
Grey Scale Manipulation

• False contouring
• Apply the sawtooth operator to the image colours
• Change gradual changes into rapid changes from
  dark to bright values
• The sawtooth operator can be implemented easily
  using the modulo function, 128 mod 108.

output
255
0
input
2
Grey Level Manipulation

• False Contouring
• Highlight local intensity variations
• Image divided into regions according to pixels
  intensities

3
Grey Level Manipulation
4
Grey Scale Manipulation

• The program may have the following codes to
  perform the sawtooth operation

For Y 1 To maxY For X 1 To maxX
NewColor (OldColor mod 60)255/60 Next X Next
Y
5
Grey Level Manipulation
Some regions become dark
Local changes are highlighted
6
Grey Level Manipulation
Area split into small regions
Local changes are highlighted
7
Histogram Manipulation

• The program may have the following codes

For Y 1 To maxY For X 1 To maxX
oldColor Pixel(X, Y) newColor
Int(CumulativePixels(oldColor) (maxGrey -
minGrey) / PixelCount) Mod 256 Next X Next Y
Where CumulativePixels(oldColor) is an array
that stores the number of pixels with intensity
less than or equal to the index.
8
Histogram Manipulation
Slightly darker
Equalized image
9
Histogram Manipulation
brighter
Equalized image