4.3.3 Piecewise Linear

The piecewise linear mapping function allows the user to build a mapping with a piecewise linear fit from a set of mapping pairs (or break points). The mapping pairs are entered as a list of from values and a list of to values (see below). The from values are a list of image values specifying the input values at the break points, while to values indicate the output values at the break points. Values are then calculated between each mapping pair entered. The values are determined by the nearest integer to the line drawn between each mapping pair. An explanation of the sample break point values shown here is given directly below the image.

*The RED break point values will map the red colormap values in the range 30 to 90 to the new range of 0 to 200. It will also map the red colormap values in the range 90 to 120 to the new range of 200 to 255. Original red colormap values below 30 and above 120 will not be incorporated into the resulting PWL mapping.

*The GREEN break point values will map the green colormap values in the range 0 to 60 to the new range of 0 to 150. It will also map the green colormap values in the range 60 to 255 to the new range of 150 to 255.

*The BLUE break point values will map the blue colormap values in the range 0 to 60 to the new range of 0 to 200. Original blue colormap values above 60 will not be incorporated into the resulting PWL mapping.

The red, green, blue, and all radio buttons allow the user to select which of the mapping components to modify. Each displayed image has three separate mapping components: one for the red, one for the green, and one for the blue portion of the mapping.

Red:
When selected, the red component of the mapping will be modified according to the break point values entered in the RED from and to fields. The green and blue components will not be changed.

Green:
When selected, the green component of the mapping will be modified according to the break point values entered in the GREEN from and to fields. The red and blue components will not be changed.

Blue:
When selected, the blue component of the mapping will be modified according to the break point values entered in the BLUE from and to fields. The red and green components will not be changed.

All:
When selected, if viewing a multi-band image each component of the mapping will be adjusted according to its respective break point values entered in the from and to fields. If viewing a single band image the left-most band with values entered in the from and to fields will be appied equally to all bands. This is the default option selected. A mutli-band image that has had its viewable bands modified so that only a single band is being viewed will be treated the same as a single band image.

From:: The left of the two columns under each band heading (RED, GREEN, & BLUE), which allows the user to enter the input mapping values. These values must be in increasing order between 0 and 255 and may be separated by either spaces or commas.
To:: The right of the two columns under each band heading (RED, GREEN, & BLUE), which allows the user to enter the output mapping values. There must be the same number of to values as from values. These values must also be in increasing order between 0 to 255 and may be separated by either spaces or commas.
Apply:: Verify the mapping pairs are valid, calculate the new mapping based on the mapping pairs entered, and apply the mapping to the displayed image.
Restore:: Reload the mapping that was applied to the image when the piecewise linear mapping function was initiated.
Linear:: Load a linear or identity mapping.
Cancel:: Reload the mapping that was applied to the image when the piecewise linear mapping function was initiated and close the piecewise linear mapping panel.
Dismiss:: Close the piecewise linear mapping panel and save the current piecewise linear mapping.