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COLOR_RANGE_MAP

Syntax | Return Value | Arguments | Keywords | Examples | Version History

The COLOR_RANGE_MAP function maps all the pixels of an image to another set of pixels, using source and target ranges to control the mapping. The mapping is performed on each image channel individually. Channel values falling within the source range are linearly mapped to the target range. The same linear mapping is applied to channel values falling outside the source range, and these values are clipped to the range of the image’s data type.

Syntax

Result = COLOR_RANGE_MAP(Image, FromColor1, FromColor2, ToColor1, ToColor2)

Return Value

Result is an array of the same dimensions and type as Image.

Arguments

Image

A 2D or 3D array of any basic type containing the input image. 2D arrays are treated as one-channel images. 3D arrays must be of the form [N x n x m] where N is the number of image channels.

FromColor1

An N-element vector that specifies the starting color in the source range, where N is the number of channels.

FromColor2

An N-element vector that specifies the ending color in the source range, where N is the number of channels.

ToColor1

An N-element vector that specifies the starting color in the target range, where N is the number of channels.

ToColor2

An N-element vector that specifies the ending color in the target range, where N is the number of channels.

Keywords

None

Examples

In this example, COLOR_RANGE_MAP will tone down the first (red) channel in an image and make a negative of an image:

; Read a TrueColor image:
file = FILEPATH('rose.jpg', SUBDIRECTORY = ['examples', 'data'])
IOPEN, file, rose1

; Tone down the first (red) channel in the image:
rose2 = COLOR_RANGE_MAP(rose1, [0,0,0], [255,255,255], [0,0,0],$
   [200,255,255])

; Make a negative of the rose image:
rose3 = COLOR_RANGE_MAP(rose1, [0,0,0], [255,255,255],$
   [255,255,255], [0,0,0])

IIMAGE, rose1, VIEW_GRID=[3,1], VIEW_TITLE='Original', $
   DIMENSIONS=[900,300], WINDOW_TITLE='COLOR_RANGE_MAP Example', $
   /NO_SAVEPROMPT
IIMAGE, rose2, /VIEW_NEXT, VIEW_TITLE='Less Red'
IIMAGE, rose3, /VIEW_NEXT, VIEW_TITLE='Negative'

; Increase the text size
ISETPROPERTY, 'text*', FONT_SIZE=40

Version History