Raster Properties Dialog:Histogram Tab
Histogram Tab
The Histogram tab allows you to view the distribution of the bands or colors in your raster. You must first generate the raster statistics by clicking the Refresh button. You can choose which bands to display by selecting them in the list box at the bottom left of the tab. Two different chart types are allowed:
- Bar chart
- Line graph
You can define the number of chart columns to use and decide whether you want
to 
Allow approximation or display out of range values
Once you view the histogram, you'll notice that the band statistics have been
populated on the metadata tab.
Tip 24 Gathering Raster Statistics
To gather statistics for a layer, select pseudocolor rendering and click the Apply button. Gathering statistics for a layer can be time consuming. Please be patient while QGIS examines your data!
