How can I limit size to a maximum rectangle (rather than just a square) when exporting in DXO OpticsPro?

Here's what the DxO Optics Pro manual has to say on this subject:

If you activate the Resize image option, you will have to choose among the following parameters:

• The maximum dimension of the output image (whether by height or width) in pixels, centimeters, or inches. One single dimension is enough for the program to maintain the aspect ratio (the proportions) of the image.

If you want to maintain the aspect ratio of your exported images, this is where you would make the adjustment. If instead you would like to change the aspect ratio, you would need to crop the images to taste before exporting them. AFAIK the Optics Pro software doesn't let you do this automatically for all the images in a given folder.

Let's say you need photo size 30,1 cm (or inch) width and 21 cm (or inch) hight in DxO PhotoLab.

1. Firstly you need to crop the image to correct aspect ratio.

• Select crop tool.
• Type to aspect ratio selection box "301:210" It's in lower left corner of editing area. That's right, you can type there as well, not just select 16:9, 2:1 etc. You can't use comma or dot for fractions, but you don't need to.
• Press enter. Now your aspect ratio is correct.
• Crop the image the way you like. Note that resizing the cropped section (crop rectangular) by dragging it from side or corners will keep the desired aspect radio in place, like expected.

2. On Export specify correct dimensions

• Select "Export to Disk" If some other export was selected then from the icon besides the Export button you can change it to "Export to Disk".
• Check "Enable resizing" checkbox
• Select "Resizing mode" to "Longest side"
• Type to "Size" the longest side, in my example "30.1"
• Select appropriate measurement unit, in my example "cm"