| Q: How does "TV, bwtable (image)" work? [message #1059] |
Sun, 13 June 1993 20:47 |
mayor
Messages: 9
Registered: May 1993
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Junior Member |
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In the April 1992 issue of IDL News on page 4, I found a "Tech Tip"
on how to make color images into Postscript halftones. It says:
TVLCT, r, g, b, /GET
bwtable = BYTSCL(.3*r + .59*g + .11*b)
SET_PLOT,'PS'
DEVICE,BITS_PER_PIXEL=8
TV, bwtable (image)
DEVICE, /CLOSE
Could someone explain how the TV command in this example works?
Also, now that I have a halftoned image, I need to draw a halftoned legend
using polyfills and I have to draw lines where I control whether they are
done in black or white. Before I switched to halftones, this was easy.
All I had to do was use the color keyword. Now, how do I refer to the
specific shades of the halftone table?
============================================================ ====================
Shane D. Mayor, Lidar Applications Group, NASA Langley Research Center,
Mail Stop 401A, Hampton, Virginia 23681-0001, USA
Internet: MAYOR@VAXINE.LARC.NASA.GOV Phone: 804-864-7598 Fax: 804-864-7790
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