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# Image Visualization

[Laboratory]

Sometimes a single display of an image is not enough to show its details. There are several complementary tools that allow exploration of the image data.

Below is a graphical representation of the image of a gull using the Display operator available in Khoros.

Original image

An image normally has a large number of pixels, that is, it is a large matrix. Sometimes one is only interested in a particular section of the image known as region of interest (ROI). Depicted below is a small image of size 10x10 extracted from around the eye of the seagull.

Extracted 10x10 region around the seagulls eye'

Clearly, a 10x10 image is very small to make good observations. The user can zoom or "expand" the region for better visualization.

Same image, but zoomed by a factor of 10

The user can also display or "print" the values of the 10x10 ROI image:

    142 174 164 218 250 255 250 252 255 255
    107 107 102  80 127 174 237 218 252 255
     90  34  24  34  34  24  51  88 127 164
     80  26  19  53  34  19  24  85 117 137
     78  76  34  44  26  26  34  24  71  90
     85  85  90  26  26  26  26  34  76  83
     88 102  90  53  26  26  34  73  85  78
    102 110 105  90  98 105 105 110 107  93
    107 115 110 110 110 117 115 110 107 102
    105 110 110 117 110 132 115 110 107 105

The user can also visualize this small image as a surface plot where the pixel intensity values are the height information. This surface can be seen below

Surface image

The user may want to plot the intensity profile of a central vertical line of the original image. The extracted line can be seen as a 1D signal. We normally visualize a 1D signal by plotting it. In the plot below we can observe the variation of the pixel values along that vertical line. Explain the three peaks in this 1D intensity profile, i. e., what do they represent in the `gull` image?

a)Original image with a vertical line; b)Intensity profile of the depicted vertical line
a) | b)

- Lab: Image Visualization