[magick-users] Best ways to decrease size of image

[Anthony Thyssen]

Mikolaj Machowski on  wrote...
| Hello,
| 
| Anthony on his incomparable pages writes very much about increasing size
| of image and how to get the best results but relatively little about
| decreasing size.
| 
| What is the best way(s) to achieve that?
| 
Actually I write about both on the resize page.

However for heavy resizing smaller, there is a seperate page.
IM Examples, thumbnails
   http://imagemagick.org/Usage/thumbnails/


| To get decent results when doing transition from 4000x4000 tiff to
| 1000x1000 jpg I am doing something like that:
| 
| convert pic.tiff -depth 8 -density 72 -resize 1000x1000 -filter lanczos
| -unsharp 1x1+0.6 -sampling-factor 1x1 -quality 90 pic.jpg
| 
| If I want better result I can make it in two or three steps and
| manipulation unsharp mask. Any ideas how to do it better?
| 
The -depth would do nothing in the above command.
while -density only sets the image density for the output image,
so probably should be given at the end with -sampling-factor.

The -filter setting however must be specified BEFORE the -resize
command!!!  It is also the default for image shrinking when no
transparency is involved, so it is not even needed!!!

  Anthony Thyssen ( System Programmer )    <A.Thyssen at griffith.edu.au>
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    "Mr. Worf, scan that ship."     "Aye, Captain... 300 DPI?"
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     Anthony's Home is his Castle     http://www.cit.gu.edu.au/~anthony/