[texhax] Transparency or reduced saturation using Graphicx ?

Andree Jacobson andree at unm.edu
Fri Mar 6 07:36:18 CET 2009

Another option is to use ImageMagick from the command line so that it  
can be scripted or put in a make file for processing multiple images.  
For example, the command:

convert +level-colors gray23,white abr-ekklhsias.pdf lighterVersion.pdf

replaces the color black with gray23 (r=59,g=59,b=59) and makes a  
linear transformation to white.
And you can antialias, apply filters, etc.

Convert accepts pretty much any image format you can dream up both as  
inputs and outputs.

More info on the color mapping at:
   (Check for "Level Adjustment by Color" about 1/3 down the page)


On Mar 5, 2009, at 3:34 pm, Pierre MacKay wrote:

> Whatever you do is not going to be easy.  What I would do (and I
> recently had to do it with 149 images) is take a screenshot, using
> import if you have it available, convert the image to TIFF, and  
> operate
> on it either with GIMP or with Adobe Streamline, to get the spines of
> all the heavy lines.  With the right Streamline settings you should be
> able to come to a fairly close approximation of the lighter penstrokes
> on the associated image.
> One other approach, which may be precluded because you seem to be
> dealing with a simple Black-White image rather than any level of
> grayscale, would be to convert it to indexed gray-scale (about 15  
> levels
> should do) in GIMP and then nip away at the outer edges by  
> progressively
> resetting the lighter grays to white.  Then harden up the remaining
> dark-gray to black pixels to simple black. I have found that an
> extremely useful way to fine down slovenly (200DPI) scans of what was
> originally line art, so that the result was an acceptable imitation  
> of a
> 1200DPI scan.  But usually you need to start with some reasonable  
> level
> of gray scale, which doesn't seem to be available in your samples.
> If only a simple graying out is needed, GIMP layers will do it.  The  
> top
> layer can be set as not fully transparent.
> Pierre MacKay
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