You can already do that with a cutout/frame.  There are some included with Qimage but you can create your own that have any style including drop shadows, wooden frames, etc.

https://www.ddisoftware.com/qimage-u/help/function.htm#cutouts

Regards,
Mike

I've created a cutout frame template in tiff format (length/height = 3/2) and it works. But this solution has probably a drawback with the stretching of the frame. If the image isn't exactly proportional to the cutout template in the length/height ratio, the frame will be stretched dis-proportionally, i.e. the distances of the outside lines from the image are not the same on the top and bottom as on the left and right hand side. For example: the cutout with a 3/2 ratio applied on an image with a 2/1 ratio results in a distance of 2mm on the left/right, as defined in the cutout template, but is reduced to less than 1.5mm on the top and bottom. Depending on the amount of stretching this can be quite visible.

I could create a series of cutouts which fit the most common image ratios to avoid very visible distortions but since I print for many other people, images come often with freehand cropping. So I cannot accommodate all ratios. Wouldn't a photo mat solution not have this problem? It stretches the mat out of the image according to the settings in the dialog box, right?