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Internet Message Format  |  1992-09-07  |  1.3 KB
  1. Path: sparky!uunet!charon.amdahl.com!pacbell.com!att-out!rutgers!munnari.oz.au!ariel!ucsvc.ucs.unimelb.edu.au!mits.com.au!alistair
  2. From: alistair@mits.com.au
  3. Newsgroups: comp.graphics
  4. Subject: Summary: Image negative to positive algorithm
  5. Message-ID: <1992Sep5.001852.3555@mits.com.au>
  6. Date: 5 Sep 92 05:18:52 GMT
  7. References: <1992Aug28.143906.3553@mits.com.au> <1992Sep1.093533.3554@mits.com.au>
  8. Lines: 35
  9.  
  10.  
  11.  alistair@mits.com.au (me) writes:
  12. > Does anyone have an algorithm for producing positive images from
  13. > negatives.
  14. > 
  15. > I would like scan in a photo negative and view it (which is much
  16. > faster and cheaper than making test prints, given that the scanner is
  17. > already there).
  18.  
  19. To convert grey scale:
  20.  
  21.     <new pixel value> = <white pixel value> - <old pixel value>
  22.  
  23. To convert colour images:
  24.  
  25.     <new red pixel value> = <max red pixel value> - <old red pixel value>
  26.     <new blue pixel value> = <max blue pixel value> - <old blue pixel value>
  27.     <new green pixel value> = <max green pixel value> - <old green pixel value>
  28.  
  29. The colour version seems to lose contrast and have an unwanted tinge. 
  30. We are currently trying to overcome this.
  31.  
  32. Thanks to everyone who has helped me, including:
  33.     Wade Schuette
  34.     Clifton Liles
  35.     Ken Yap
  36.     Sean Malloy
  37.     Brian Dockter
  38.  
  39. Thanks,
  40.  
  41. Alistair Grant
  42.  
  43. Internet:     alistair@mits.com.au
  44. Alternate:    alistair%mits.com.au@ucsvc.ucs.unimelb.edu.au
  45.