LR2 Mogrify will do this from Photographers' Toolbox a post processing plug-in for export. You will have to experiment with the settings within Mogrify between canvas size and height and width to get the results you require for the different output versions but can create your export templates once you have them. For example I batch export JPEG files from varied aspects ratio images including mixed landscape and portrait to a single aspect ratio file. This pads borders to maximise the achievable image in one of the dimensions with a free choice of colours (far beyond black and white) using the eye dropper tool.
↧