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crop and extact to png
Posted: 2012-01-03T11:08:20-07:00
by imaggie
The above was created by the following command:
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convert -gravity NorthEast -crop "600x600+0+0" biche.jpg biche.png
It seems IM is producing something that has a different meaning to GIMP.
IM bug, GIMP bug or png spec abiguity?
thx
Re: crop and extact to png
Posted: 2012-01-03T11:26:02-07:00
by glennrp
Use the +repage option to get rid of the offset information left over from the cropping operation. Also it's best to put the processing options after reading the input image:
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convert biche.jpg -gravity NorthEast -crop "600x600+0+0" +repage biche.png
Re: crop and extact to png
Posted: 2012-01-03T13:20:19-07:00
by imaggie
many thanks for clearing that up.
How should I have know to do this? I have gone over the doc for -extract and crop many times now and see no indication that there is some residual information nor of the need to "repage".
Re: crop and extact to png
Posted: 2012-01-03T14:30:42-07:00
by glennrp
imaggie wrote:many thanks for clearing that up.
How should I have know to do this? I have gone over the doc for -extract and crop many times now and see no indication that there is some residual information nor of the need to "repage".
I suppose it's easy to miss, but the last paragraph under the -crop section of the command-line options says
- It might be necessary to +repage the image prior to cropping the image to ensure
the crop coordinate frame is relocated to the upper-left corner of the visible image.
I don't know if it will help much, but I'm adding
- This is especially true when you are going to write to an image format such
as PNG that supports an image offset.
to that paragraph.
Re: crop and extact to png
Posted: 2012-01-03T14:39:42-07:00
by imaggie
It does indeed.
IM has a learning curve like the foothills of the Himalayas , looks like I'm getting out of breath !
Many thanks.