CS 474/674 Midterm Examination, October, 2001, Prof. Carl G. Looney

[1] (a) Draw a graph of a nonlinear transformation that contracts very dark and very light shades of gray but stretches the middle gray levels out to a wider range. (b) Draw a transformation that outputs the negative of the input image.

(a) (b)

[2] Check which of the following image properties can be determined from a histogram.

(a) ___ gray level range is too small (b) ___ too many pixels are too light (c) ___ too many pixels are too dark

(d) ___ edges are not sharp enough (d) ___ image is too smooth (e) ___ there is a lot of noise

[3] An 8-bit pixel value in a color image file is 10001110. How does this value determine the R, G and B colors for a pixel?

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[4] Images A and B are to be put on a Web site. The first is a medical image whose details are important and the second is a photograph of a mountain scene. It is desired to compress these as much as possible. What type of file should be used for each? (a) The file format for A should be ______________. (b) The file format for B should be ________________. (c) Is there an alternative format for either of these? ___________________________

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[5] Design a 3x3 mask that detects edges in when moving from left to right (horizontally). Design a 3x3 mask that detects edges when moving from top to bottom (vertically). Show the sum of these masks below on the right.

+ =

Clearly and briefly, what does the sum mask do? _________________________________________________

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[6] Consider the mask given below. (a) Describe what it does to an image under mask convolution.__________

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(b) Break this mask into two masks whose sum is the mask shown and the first mask boosts the original image

by a standard amount.