Create a histogram plot of the input image. A histogram is a plot of the number of occurrences of individual pixel values. The higher the curve, the more pixels have that value. If a window is specified, only the pixels within the window are included in the calculation of the histogram.

The input image may have any number of bands. A histogram curve is plotted for each band, with an individual color for the first 6 bands. Any further bands are rendered in black. The histograms are plotted in a separate window.

This window may be adjusted in size. The mouse wheel will magnify the plots and they can be dragged with the left mouse button. If the “shift” key is held down, the cursor will show the x- and y-values of the plot.

If another module is attached on the output, then the image is passed through.

input image: multiband, Byte, or Integer output image: same as input

Example: the following 50×50 image has a range of 8 bit with values ranging from 0 to 255. The histogram displays that the most of the pixels have light gray values. there are some pixels which are neutral gray or darker gray. This makes sense as most of the pixels represent the brighter background and only a small amount of pixels represent the writing. Form the total of 2500 pixels in the image (50×50) 81 have the same pixel value of 203.