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Lighting Issues...
Bad lighting can really cause problems with most image analysis techniques (esp. when thresholding). Imagine
if a robot were to suddenly move under a shadow and lose all control! The best vision techniques try
to be more robust to lighting changes.
To
understand some of those issues lets look at two histograms from a straight line image from the previous
slide. Next to each of these images are the images histogram. The histogram of an image is a graphical
representation of the count of different pixel intensities in the image.
As you can see, histograms for lighter images slump towards the right (towards the 255 or highest value)
whereas darker images have histograms with most pixels closer to zero. This is obvious but using the
histogram representation we can better understand how transformations to the image change the underlying
pixels.
 
 
The next step is to see if we can correct these two images so that they look closer to one
another. We do that by normalizing the images ...
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