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A satisfied customer

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• Kerrypng at 2006-05-20 07:02
  On another graphics forum I pointed out that the PNGout plugin for IrfanView has a nice GUI and compresses better than pngcrush. This was the response:
  
  "Oh wow... I tried out the PNGout and... just wow."
  
  On a different point, I noticed something unexpected and did a search of this forum to see if it had been mentioned before. PNGout generates a different palette order if I start with a 24 bit BMP image than if I start with a PNG created by Web Image Guru. Consequently, the two resulting output file sizes are different. The original palette order in Web Image Guru's PNG was different to both PNGout versions. How come?
  Edited at 2006-06-01 04:41
• Awesoken at 2006-05-20 12:42
  Thanks for the free advertising : )
  
  Short answer: If you run pngout by specifying the /c3 option explicitly, the palettes will match. There are actually 3 ways to specify palette order in PNGOUT and PNGOUTWin. Study this chart:
  

  PNGOUTWin:     PNGOUT:        Description:
  
  -----------------------------------------------------------------------------
  
  1. Optimize    pngout ..      Starts with palette from file if paletted; inconsistent output
  
  2. Regenerate  pngout /c3 ..  Regenerates palette from scratch - consistent output
  
  3. Preserve    pngout /kp ..  Doesn't modify palette. Uses method #1 or #2 if no palette

  
  
  The PNG from Web Image Guru must be a paletted image. The default is optimize, where PNGOUT tries to re-order palette entries to save on Huffman table storage.
• Martin at 2007-05-18 01:09

  Re: A satisfied customer

  When using /c3 /kp, /kp takes priority, right?
• Awesoken at 2007-05-18 03:34
  It's easy enough to test with file compare. The answer is yes.