Why do histogram equalisation programs usually not produce images with flat histograms?
Thanks
Histogram equalisation
Histogram equalisation
Hello,
Why do histogram equalisation programs usually not produce images with flat histograms?
Thanks
Why do histogram equalisation programs usually not produce images with flat histograms?
Thanks
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snibgo
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Re: Histogram equalisation
It is flat, in the sense that the range 0-50 has the same number of pixels as the range 50-100, and 100-150, etc. In addition, the mean is at about 50%.
Although the peak counts are higher at the low end, you'll also see that they are very sparse: there only 6 values in the range 0-50. In contrast to this, there are nearly 50 values in the range 200-250.
This is a typical situation when the input is JPEG, at 8 bits/channel/pixel, and most pixels are at one end of the value range. When they are spread evenly ("equalised") we get a comb-shaped histogram at that end.
Although the peak counts are higher at the low end, you'll also see that they are very sparse: there only 6 values in the range 0-50. In contrast to this, there are nearly 50 values in the range 200-250.
This is a typical situation when the input is JPEG, at 8 bits/channel/pixel, and most pixels are at one end of the value range. When they are spread evenly ("equalised") we get a comb-shaped histogram at that end.
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