I need an image that is 8640 pixels wide:
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)
First I paste a black graphic into the image and save it
When I then re-open it, the black line is gone again