DBImageHistogram

Demonstrates how to compute a histogram of an image.

Remarks

The following example illustrates how to compute a histogram of the image data in channel 1 of irvine.pix, sampling only the pixels under the mask in bitmap segment 9 (lake training area). The histogram has 256 entries from value 0 to 255. If values are outside the range, they will not be included in the histogram. After the histogram is computed, all bins in the histogram with a non-zero pixel count are reported along with the image value corresponding to that bin.

Code

 local int histogram[256], tfid, i, pixelcount

 tfid = DBOpen( GetPCIHOME() + "/demo/irvine.pix", "r" )

 pixelcount =  DBImageHistogram( tfid, 1, 256, histogram, 0.0, 1.0, 0, 9 )

 call DBClose( tfid )

 for i = 1 to 256
   if( histogram[i] <> 0 )then
     printf "%3d - %d\n", i-1, histogram[i]
   endif
 endfor

Output

48 - 1
51 - 1
52 - 5
53 - 22
54 - 53
55 - 86
56 - 132
57 - 79
58 - 56
59 - 16
60 - 7
61 - 3
62 - 6
65 - 1
69 - 1
80 - 1
Total pixels: 470