This topic describes how to interactively stretch an image in an ENVI Classic display group. See Stretch for the recommended method for applying contrast and interactive stretches to images in ENVI.

An Input and an Output histogram appear in the Interactive Contrast Stretching dialog. They show the current input data and applied stretch respectively. Two vertical dotted lines mark the current minimum and maximum values of the stretch.

For color images, the histogram color matches the color of the selected band (the red band displays by default). The bottom of the Interactive Histogram window shows the stretch type and the histogram source. To view the histogram for the green or blue bands of a color image, select the G or B radio button.

  1. To automatically apply stretching or histogram changes to your image, select Options > Auto Apply. Toggle this option off if you want to apply changes only when you click Apply.
  2. Use the Options menu and interactive mouse functions to set preferences for your stretch and to view details in the Interactive Histogram window.

  3. To view the current pixel value (DN) and the number of pixels, percentage, and cumulative percent of pixels for that specific value, click and drag within the histogram.

For complete details on all the functions you can perform in the interactive stretching dialog, refer to the topic "Using Interactive Stretching" in ENVI Classic Help.