Working with the histogram when displaying raster data

You can work with the histogram when displaying raster data with the RGB Composite or Stretched renderers. The histogram displays the pixel values on the x-axis and the count on the y-axis. The input pixel values are displayed in gray, and the output pixel values are displayed with a color. When there is no histogram stretch, the input pixel values equal the output stretched pixel values. The greater the stretch, the larger the difference between the input pixel values and the output pixel values.

There are a few different methods you can use to apply stretches to the histogram:

You can also click within the histogram to place breakpoints. Drag these breakpoints to the appropriate location to apply a stretch to certain values. If you know which values you want to stretch, place the pointer over the histogram and locate the input values along the x-axis of the graph line. Place breakpoints at these points, then move the graph line up to the required output value on the y-axis. To delete breakpoints, hold the pointer over one, then click and drag the breakpoint off the graph line.

Click the Information button Histogram Information button to see information about several columns of the histogram. By clicking and dragging within the histogram, columns are highlighted and the information is shown in the Info section of the dialog box.

By clicking the Smooth button Smooth histogram button, you can smooth out the stretch that has been applied to the point stretch. The result will be a smooth curve rather than jagged transitions. You can continue to click this button until you reach the desired smoothness.

By clicking the Cumulative button Cumulative button, the histogram will be displayed with a cumulative output (y) along the input (x) axis.

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