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I need an image that is 8640 pixels wide:

http://i.stack.imgur.com/uoS28.png

Whenever I add something to the 8640 pixel wide image (e.g. in Preview or pixelmator) and save it, it gets cleared and when I re-open the image, I get an empty image.

My question is how I can edit images like this on the Mac (without a Photoshop license)

Example:

  1. First I paste a black graphic into the image and save it enter image description here

  2. When I then re-open it, the black line is gone again enter image description here

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Did you try pasting something much larger than a line? Or, making sure that Preview is viewing the image at its actual size? I suspect that the line is getting hidden, as it is too small to be seen when the entire image is fit into the window like that. –  Kent May 28 '13 at 23:51
    
@Kent I did see the black line when I pasted the image into this. Believe me I have tried in various ways. The 1 pixel high image is just as an example for this question. –  Besi May 29 '13 at 13:04
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1 Answer 1

up vote 1 down vote accepted

I could reproduce it with PNG or JPG files where one side was 8193 (2^13+1) pixels or longer and the other side was 64 pixels or shorter. When I saved the files in Preview, PNG files became transparent and JPG files became solid white.

As a workaround, you could make an image 65 pixels or taller in Preview and then crop it with ImageMagick:

convert 1.png -extent 8640x10 2.png
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