Ron Savage on wrote...
| On Wed, 31 May 2006 16:25:55 +1000, Anthony Thyssen wrote:
|
| Hi Anthony
|
| > You don't specify the logo.jpg source...
|
| My fault. I'm using the one shipped with IM, in the images/ dir.
|
| Generating it via the command line gives a much larger version...
|
Hmmm... Using the latest IM 6.2.7-9 beta (compiled for FC4)...
convert /usr/share/doc/ImageMagick-6.2.7/images/logo.jpg \
-crop 70x70+50+50 out.png
display out.png
Yep I can see the black pixel you refer to...
Lets see what is beyond the cropped region.
convert /usr/share/doc/ImageMagick-6.2.7/images/logo.jpg \
-crop 70x70+49+49 out2.png
display out.png
Hmm more black pixels, thats good, it is not an artifact.
Lets go back to GIF...
convert /usr/share/doc/ImageMagick-6.2.7/images/logo.jpg \
-crop 70x70+50+50 out.gif
display out.gif
I can see one darkish pixel!
Lets try JPEG...
convert /usr/share/doc/ImageMagick-6.2.7/images/logo.jpg \
-crop 70x70+50+50 out.jpg
display out.jpg
Yeap a single dark pixel...
I can find nothing wrong, other than some slight color changes due to
color quantization (GIF) and lossy compressing (reading source, and JPEG
output). Causing some slight color differences, between the formats...
Part of this may be due to the use of a JPEG image source.
That is not a good choice for difinative image tests!
One question I have not had answered was if color changes due to JPEG
lossy compression happens during read, or on write of the image.
Probably on read, in which case images extracted from a JPG file may be
slightly different depending on machine, and library versions used, or
even different on the same machine due to some and ranomization effect.
Anyone know?
Anthony Thyssen ( System Programmer ) <[EMAIL PROTECTED]>
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The law of similarity made any map a magical instrument.
-- Rick Cook, "The Wizardry Compiled"
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Anthony's Home is his Castle http://www.cit.gu.edu.au/~anthony/
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