JPEG's technically limited to 64x64k dimensions per the spec (65500 pixels with libjpeg and libturbojpeg), so if you want arbitrary software to be able to open

JPEG's technically limited to 64x64k dimensions per the spec (65500 pixels with libjpeg and libturbojpeg), so if you want arbitrary software to be able to open images in that format, you'd be limited to that...