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March 2005
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2005.03.03 16:30 "Re: Tiff G4", by Bob Friesenhahn
On Thu, 3 Mar 2005, Beppe Costagliola wrote: > I though that I could use "tiffcp -c none" and then "tiffcp -c jpeg" but > unfortunately I don't have a tiffcp working and I could not see if it is > possible. JPEG is designed to compress "natural scene" images. Typically these are 8-bit gray or RGB images. It is *terrible* at compressing one bit images and does very poorly with line drawings. > About "re-sampling/filtering" do you know any open source (in C) that does > the job ? Any image processing package which supports filtering algorithms and thresholding will do. One such package is GraphicsMagick (http://www.GraphicsMagick.org/). I hear good things about a package called VIPS (http://www.vips.ecs.soton.ac.uk/). You can use a filter to "blur" the image or remove "speckles" and then apply thresholding in order to obtain a smoothed monochrome image with less detail, but which compresses better. If your image is based on some sort of a drawing, you may find a tool like autotrace (http://sourceforge.net/projects/autotrace/) to be valuable. It will take lots of trial and error and lots of CPU time to use autotrace. Autotrace would convert your image to a high level vector format which can be re-rendered in a "smoother" fashion so that it compresses better. The SWF file displayed via http://www.springcreekcommunity.org/map/body.html was accomplished using autotrace. Bob ====================================== Bob Friesenhahn bfriesen@simple.dallas.tx.us, http://www.simplesystems.org/users/bfriesen/ GraphicsMagick Maintainer, http://www.GraphicsMagick.org/