Claus Cyrny on  wrote...
| > It works fine, but I find that the antialiasing is quite bad.
| > You can look at the result here :
| > http://img513.imageshack.us/img513/7528/convertvs8.png
| 
| Is this image representative for the images you have to convert?
| Why don't you convert them to indexed (palette-based) images,
| say, 64 colors? Thus, the TIFFs will become visibly smaller in file size.
| (I wouldn't recommend '-dither', though; you'll only be getting
| much noise in the images that way.)
| 
[SOAPBOX START]
Yes though if you are using 64 colors, why not use the more unuversally
accepted GIF image format instead!!!!   TIFF is so bloated with features
only photoshop can handle all valid forms of TIFF.  I would steer clear
of that format unless you are specifically working with photoshop, or
the application accepts no other, better defined, image file format.
[SOAPBOX END]


Error Correction Dither (-dither) works well, but falls down when the
number of colors becomes too small, causing the colors to become wildly
different.

For more information on the E-Dither, and its known problems see
IM examples, Error Correction dither
  http://www.imagemagick.org/Usage/quantize/#dither_error


The other practical type of dithering, Ordered Dither will work well
with a low number of colors, producing a tigh hash pattern on images of
two or three colors.

Unfortunatally the form of O-dither that is available in ImageMgaick is
restricted to a mathematically defined color pallete, and not the 'best'
or user defined set of colors.   I should know, I was the one to
re-program the current ordered dither from purely bitmap to the
'posterized' colors version, and allow user defined threshold maps.

See IM Examples
   http://www.imagemagick.org/Usage/quantize/#od_posterize

And my development notes page
   http://www.imagemagick.org/Usage/

I am looking for information on a color palette restricted ordered
dither,  which I know exists because I see its results in minimal color
images (especially the very old PC icons).

If any one know more information on such a dither, or can point me to
such information whether it is on the WWW, or in academic research papers,
then PLEASE let me know.


  Anthony Thyssen ( System Programmer )    <[EMAIL PROTECTED]>
 -----------------------------------------------------------------------------
  At 300 dpi you can tell she's wearing a swimsuit.
  At 600 dpi you can tell it's wet.
  At 1200 dpi you can tell it's painted on.
  I suppose at 2400 dpi you can tell if the paint is giving her a rash.
                                                      -- Joshua R. Poulson
 -----------------------------------------------------------------------------
     Anthony's Home is his Castle     http://www.cit.gu.edu.au/~anthony/

_______________________________________________
Magick-users mailing list
[email protected]
http://studio.imagemagick.org/mailman/listinfo/magick-users

Reply via email to