22-10-2012, 04:07 PM
Point Processing
Point Processing .ppt (Size: 2.09 MB / Downloads: 21)
What is point processing
Grey level enhancement
Process one pixel at a time independent of all other pixels
For example used to correct Brightness and Contrast (remote control)
How to set the greylevel mapping
A Histogram is a discrete function ,
is the number of pixels with the k-th gray level
is the total number of pixels
Histogram entry gives the probability of gray value k of appearing in the image.
Improving contrast
Humans cannot tell the difference between greylevel values too close to each other
So: spread out the greylevel values
This is called histogram stretching
Exercises
Questions to the lecture?
What was good about the lecture and what could have been better?
Discuss the PE-questions
Download ImageJ: http://rsb.info.nih.gov/ij/
Use ImageJ to play around with greylevel mapping, histograms and thresholding. Make sure you understand these concepts!
How will the algorithm look like if two threshold values are used instead of just one?
Is it wise to have a binary image consisting of 0s and 1s?
Finish the exercises from last time