I thought I had posted this suggestion several days to a week ago, but I cannot find any reference to it.
I would like the option to place album art in mp3tag without modifying the aspect ratio of the original image. For images that are wider than they are tall, this might require adding equal height white background "bars" above and below the image. This should not have to be done outside of mp3tag before placing the cover art.
This feature would allow images to be placed that retain their original aspect ratio, avoiding the unattractive distortion of the image along the horizontal axis. It would also prevent distorting copyrighted art used in the cover. Note that some on-line retailers such as CDBaby and Amazon appear to require square images in their store presentation. To meet this apparent requirement without distorting the cover art would be a very good feature.
In conjunction with this suggestion, I would like to see an optional setting to limit the maximum pixel dimension along the longest axis, typically the horizontal axis, in order to keep the sizes of the resulting files as small as practicable while maintaining desirable resolution. In my case, I think it wise to limit the image size in the horizontal direction to something like, say, 800 pixels. This would require downsizing the image when it was larger than the desired setting along the longest axis.
Dennis, aka "d2b"