firefox: saving high resolution images from a html-canvas
There is a recent trend in web-design that is really worrisome. A html canvas is used to load pictures and you
can pan or zoom in/out but you can't save these pictures. This is a very strange trend. Web browsers can display
image files natively.
In some cases the html designers offer a download button but that's rare. The panning and zooming is nice for small
screens but using a local image viewer would still be better.
The firefox "responsive design mode" to the rescue: If you had a really huge screen and the image inside the html-canvas
spans the entire screen then you would be able to take a screenshot with a good resolution.
The "responsive design mode" allows you to set the screen size. You can set it e.g to 5000x4000 pixel and that might be
bigger than your actual screen but the screenshot feature inside the "responsive design mode" will still save the entire
5000x4000 pixel screen even if you don't see everything on your physical screen. This way you can save an entire image in
full resolution.
Take a screenhot of a very large virtual screen
Steps:
Open web page in "responsive design mode"
Set a very large screen size, e.g 5000x4000
Position the image in the html canvas and zoom it the way you want it
Take a screenshot from within firefox
You get a screenshot of the entire screen, a 5000x4000 pixel image
