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  1: Introduction
  2: Simple example
  3: Invocation
  4: Finer Control
  5: X-Y Plots
  6: Contour Plots
  7: Image Plots
  8: Examples
  9: Gri Commands
  10: Programming
  11: Environment
  12: Emacs Mode
  13: History
  14: Installation
  15: Gri Bugs
  16: Test Suite
  17: Gri in Press
  18: Acknowledgments
  19: License

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9.3.24: `mask'

`mask the image [to {uservalue .u.}|{imagevalue .i.}]'

Examine both the image and the mask pixel by pixel. For any pixels which have a mask value of 1 (which indicates an invalid region of the image), change the image value. If no `to' phrase is present, change the image value to 0 in pixel units. If the `to uservalue .u.' phrase is present, change the pixel to hold the imagevalue that corresponds to this uservalue (see `set image range' command for a discussion of this correspondance). If the `to imagevalue .i.' phrase is present, change the pixel to hold that imagevalue (in range 0 to 255 inclusive for 8-bit images).

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