crop and extact to png

[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

[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

[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".

[glennrp]

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.

[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.