====== Histogram ======
Histogram plots the histogram of the input image: the number of pixels that have each value. The higher the curve, the more pixels have that value. If you enter a "window", only the pixels inside it are counted.

The input can have any number of bands, with byte or integer data. A curve is plotted for each band, with its own color for the first 6 bands; any further bands are black. The plots appear in a separate window:
  * The window can be resized.
  * Turn the scroll wheel to magnify the plots, and drag them with the left mouse button.
  * Hold down **Shift** to show the x and y values at the cursor.

If another module is connected after Histogram, the image is passed on unchanged. For a quick histogram of a region, you can also right-click a window in Show and choose **Histogram**; see [[basic_level:show:display_window|Show – The Display Window]].

===== Example =====
<WRAP group>
<WRAP half column>{{ :basic_level:enhancement:image1.png?nolink&400 |A 50 × 50 pixel, 8-bit image of writing}}</WRAP>
<WRAP half column>{{ :advanced_level:image1_histogram.png?nolink&400 |The histogram of that image}}</WRAP>
</WRAP>

This 50 × 50 pixel image has 8-bit values from 0 to 255. The histogram shows that most of the pixels are light gray, with some mid-gray or darker pixels. This makes sense: most of the pixels are the brighter background, and only a few are the writing. Of the 2,500 pixels in the image, 81 have the value 203.