Image Statistics; Histogram - Smartek Vision Giganetix GC Series User Manual

7.1 Image Statistics

7.1.1 Histogram

A histogram is a graphical representation of the distribution of all intensity values that can be found in an
image. The histogram graph is plotted using the Cartesian coordinate system. The x-coordinates are in
n
a range from 0 to 2
to an intensity value that exists in the image. The y-coordinates are in a range from 0 to image_width x
image_height, describing the total numbers of pixels for each pixel value found in the image.
Figure 126 illustrates a histogram of an 8-bit monochrome image (1):
The horizontal x-axis of the graph (2) contains the intensity values with a range from 0 to 2
to 255. The vertical y-axis shows the count of pixels with the corresponding intensity. There are 5774
pixels that have the value 80 in the image (1) for example.
While the graph (2) allows a quick visual interpretation of the distribution of pixels in the image, the
histogram table (3) gives more exact information about the count of specific intensities. For the pixel
value 80 there are exact 5774 pixels located in the image while other intensity levels, are not even
present, like 1 and 2.
Pixel Count
value
0 768
1 0
2 0
... ...
80 5774
81 4535
... ...
255 1191
Histogram table
- 1, where n is the bit depth of a pixel value. Each x-coordinate can correspond
Number of pixels with
value 80 = 5774
Figure 126: Source image with histogram graph and table
7 Image Processing in GigEVisionSDK
Pixel value = 80
160
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SMARTEK Vision Giganetix User Manual Version 2.1.4
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