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\majorheading{ppm2atkimage: convert a PPM file to ATK image format

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\section{Overview

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The \typewriter{ppm2atkimage} program is a filter that converts between the 
various PPM formats that are widely used: portable pixmap (ppm), portable 
graymap (pgm), portable bitmap (pbm), etc.  The output of this filter is an 
ATK image datastream suitable for inclusion in an ATK document or viewing with 
EZ.


\section{Quick Reference}


\typewriter{% xwd2atkimage -gif foo.ppm > foo.img

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\subsection{Arguments:}


\indent{-gif		specifies that the resulting ATK image be saved as GIF

-jpeg		specifies that the resulting ATK image be saved as  JPEG JFIF 

-qN		specifies the save-quality parameter to the JPEG compressor, where N is a 
value between 0 and 100.


Any argument to ppm2atkimage that doesn't begin with the dash character ('-') 
is considered to be the name of the input file.  If multiple files are listed, 
only the last one in the list is used.  If no file is specified, input is read 
from the standard input.

}\section{
Save Formats

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The ATK image class can save image data in one of two different native 
formats: GIF & JPEG JFIF.  


\leftindent{The GIF representation uses a run-length encoding that makes it 
very efficient for storing particular types of images.  Run-length encoding 
(rle) is a compression technique that takes advantage of regions of constant 
color by gathering them together and representing them as a intensity:count 
pairs.  So, rle is best applied to drawings, cartoons, and images with few 
different colors (<= 256).


The JPEG JFIF representation is best suited for another class of images, those 
with many closelt seperated colors as would be generated from a photo of a 
real world scene.  Further, JPEG compression is parameterized on a quality 
value (0-100) that is used to specify a compression/quality tradeoff.  You can 
get significant savings in image file size by lowering the quality value, 
while still retaining a realistic looking image that is often indistingishable 
from the original.

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The image view class allows you to specify which save format to use for a 
particular image or you can employ the \bold{ImageSavedFormat} preference, 
which can have a value of either \bold{gif} or \bold{jpeg}.  Furthermore, when 
the JPEG format is chosen, you can also set the save-quality parameter via the 
image view or employ the \bold{ImageSaveQuality} preference option.


\section{Program Author}

\leftindent{
}\indent{Gary W. Keim (gk5g+@andrew.cmu.edu)

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\section{Related tools}  


Select (highlight) one of the italicized names and choose "Show Help on 
Selected Word" from the pop-up menu to see the help file for:


\leftindent{\helptopic{image}

\helptopic{xwd2atkimage}

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