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| Tuesday, July 01, 2008 |
| Activity 4: Image Enhancement by Histogram Manipulation |
The image I used was the controversial Lochness Monster picture that was a huge hit for paranormal enthusiasts worldwide when it was released decades ago - a poor contrast, gray scale photograph.
In this activity, my goal was to enhance the image by either stretching the histogram such that the highest value is 255 and the lowest is zero or by linearizing the image's cumulative distribution factor or CDF. Using the histogram code from the previous experiment: when we normalize the histogram we get the probability density function or PDF:
Evaluating the PDF with respect to the image's parameters we get the cumulative distribution function or CDF:
Using backprojecting which is done by acquiring the pixel value of each pixels and replacing it with the y-axis value of the CDF at that particular pixel value. We therefore obtain a new PDF and consequently a new CDF giving us an enhanced version of the original image:
Notice that the new image has a sharper and more pronounced contrast than the original image.
Using other Non-linear methods besides backprojecting gives a smaller image with good contrast almost similar to the first image. With PDF and CDF given by:
I performed this activity with the help of Jeric and Julie Ting for the codes. Due to the good correspondence that my enhanced images have with the original, I give myself 10/10 neutrinos! Yey!
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posted by poy @ 7:00 AM  |
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