Quantizing bitmap images; Re: SX-64 Service manual

From: Marko Mäkelä (msmakela_at_gmail.com)
Date: 2007-06-11 10:58:44

On Mon, Jun 11, 2007 at 04:17:38AM +0000, William Levak wrote:
> I can extract the images to .ppm  with XPDF.
> The first page is 6592 x 5173 x 24 bit, file size 102,301,265.
> I can't find anything to open this file.  I run out of memory.

Would it help to convert the image to grayscale with pnmtopgm
from NetPBM <http://netpbm.sourceforge.net/>?  You might also
want to try ppmquant.  It might also be possible to convert
to PNG and use something like pngcrush, pngnq or pngquant, but
I believe that it would be more efficient to do the quantization
on the uncompressed data.

Some 10 years ago, I noticed the lack of memory-efficient image
processing tools on GNU/Linux.  Back then, it was real trouble to
handle an A4-sized scan, when 128 MiB of RAM was considered huge.
I have the impression that most free image manipulation tools use
a fixed word length, for example, the GIMP might use 8 bits per
component.  I hope that all bitmap tools will some day support a
variable word length, say, 4, 8, 12, or 16 bits per component
(12 to 48 bits per pixel in RGB).


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