cmttoppm: CMT to PPM Converter

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Based on my analysis of CCD used in ES-1000, I have made a converter from CMT (internal image format of ES-1000) to PPM (an image format common on Unix). It is tested only on Linux, but as all it does is to read/write files it should be easy to let it run on other OSs.
Besides CMT, it can also convert IMG files which is the standard file format of LXDC.


C source of cmttoppm is here. It can be compiled as follows:
gcc -O2 -lm cmttoppm.c -o cmttoppm
Currently the only document for cmttoppm is this page; please save this page to a local file. I am going to write a manual later.

Summary of cmttoppm

Following command line converts a CMT file to PPM file:
cmttoppm [options] [CMT_file [PPM_file]]


-s (default: 1.5)
Correction parameter of saturation (make this bigger for louder colours)
-G (default: 0.5)
Gamma parameter (make this smaller to assign more contrast to dim areas)
-r, -g, -b (default: 0.64, 0.58, 1.00 accordingly)
Correction parameters of red, green, and blue (make each colour stronger)
-n (default: 3)
Percentage of pixels to ignore at lower and upper bound (make this bigger for higher contrast)
Specifies lower bound explicitly
Specifies upper bound explicitly

Processing output

PPM files generated with cmttoppm can be used on many image manipulation programs on Unix such as Imagemagick, Netpbm, or xv.

cmttoppm does not change aspect ratio as images are usually magnified or reduced anyhow before being used; please enlarge images vertically by 156% using some image tool.
Adding some sharpness to the picture is a good idea to make it look better.

For example, convert command of Imagemagick can used with following options to produce an output similar to Chinon driver:

convert -geometry 100%x156% -sharpen 80 src.ppm dest.ppm

Known bugs

  1. Pictures taken against sun looks sometimes greenish.
    You can get around this phenomenon by executing cmttoppm again with a smaller value to -h option; 2/3 of the default value can be suggested. Default -h value is shown as "high_i = ".
  2. Does not support 320x240 pixels mode.

Sample output

This CMT file is converted by cmttoppm and Chinon driver to following outputs. They look similar enough to my untrained eyes.

Several pixels on the top/bottom/left/right borders of CCD of ES-1000 have incorrect colours. As opposed to Chinon driver which cut these pixels off, cmttoppm keeps them with their incorrect colour. This makes output of cmttoppm to 500x375 pixels instead of 493x373 of Chinon driver.

Output image of cmttoppm

Command line to generate it:
cmttoppm 960812-2.cmt 960812-2.ppm
convert -quality 85 -sharpen 80 -geometry 100%x156% 960812-2.ppm 960812-2-hideki.jpg

Output image of Chinon driver

Command line to generate it:
(Read 960812-2.cmt on Windows driver and store it to 960812-2.tif)
convert -quality 85 960812-2.tif 960812-2-chinon.jpg

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