[magick-users] is this a bug?

[Anthony Thyssen]

"Amadeus W. M." on  wrote...
| I'm trying to crop a a pgm image like this:
| 
| convert -crop 50x50 lena.pgm tmp.pgm
| 
| The resulting pgm has white value = 65535 rather than 255:
| 
| head -3 tmp.pgm
| P5
| 50 50
| 65535
| 
| even though the original is ok:
| 
| head -3 lena.pgm 
| P5
| 208 222
| 255
| 
| Also, the resulting tmp.pgm image has size 92722 bytes rather than
| 50x50=2500 as I'd expect (without the header). Despite all this, xv
| displays it correctly. I don't understand. What's going on? 
| 
| Thanks!
| 
You are using a Q16 version of IM which premotes all color values to 16
bit quality (-depth 16).

The thrid line just says what the maximum value is for the data
that follows.

If you want it 255 you can set   -depth 8    before saving the PGM file.

At this time there is no use of  -quality    to set an odd quality value
for PGM, PPM, PNM, and PAM  images.

Eg: a Maximum value of 15 should be posible using  -quality 16 but this
has not been implemented.  It is on the 'Future Proposals' page however.
 http://www.cit.gu.edu.au/~anthony/graphics/imagick6/bugs/future/#quality


You can select between  the plain text PGM (P2)  and binary PGM (P5)
by using the  -compress  setting.

For example --- a plain text PGM  (P2)...
  compress pattern:fishscales -compress None  PGM:-

Or a binary PGM image (P5)
       compress pattern:fishscales PGM:-
or     compress pattern:fishscales +compress PGM:-


  Anthony Thyssen ( System Programmer )    <A.Thyssen at griffith.edu.au>
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