[gentoo-user] resizing multiple images with adding a frame as needed

[hw]

Hi,

suppose I have a number of images that need to be displayed side by side 
in a nice layout.  The images are of different sizes and have different 
aspect ratios.

To fit the images into the layout, I can scale the images either by 
height or width or by percantage, and they will look messy in the layout 
because I need to keep their aspect ratio when scaling them.

So what I need to do is put a frame around each image just as needed 
when scaling it so that I will end up with all the images having the 
same size while maintaining their aspect ratio.

I guess 'convert' (from imagemagick) or 'ffmpeg' can do this, yet I 
couldn't find out how.


(In this particular case, I would set a default size to scale all images 
to rather than doing something more complicated like examine all images 
in advance to compute a good size to use from the largest or smallest 
one or from their average dimensions.)


Any ideas how to do this?