Hello, so here's my question. Say I have a 2000x3000 pixel photo and I want to add a white border all the way around the image that is 5% of the smallest dimension (so, 5% of 2000 = 100 pixels). I want the original image to be completely preserved without resampling or cropping.
In Lightroom, there is the Scale feature under Geometry. If I slide it to 90%, the image shrinks 5% from each edge, leaving a white border. However, since the long end of the photo is 3000 pixels, the white border ends up being 150 pixels on 2 sides and 100 pixels on the other 2 sides. I just want 100 pixels all the way around. I also wonder what is actually happening to the shrunken image - is it being resampled? If so, what is the algorithm that is being used - eg bicubic, bilinear?
In Photoshop, I can instead add to the canvas size - it's simple enough to expand the canvas by 100 pixels in all directions. However, the image must then be resampled upon export, which degrades the original image quality.
Another alternative that I've seen is using the Print module of Lightroom Classic, which is quite tedious for batches of photos with varying dimensions, and as far as I can tell there is no analogous Print module in the new Lightroom (CC).
Is there a simple way to do what I want that I'm missing? If not in the Adobe ecosystem, does anyone know of a 3rd party software that does this without altering the original image?