Export JPEG of variable resolution

Starting with full frame 45 Mpixel raw images, I crop some images, but not all. How to export to JPEG the processed images all at once, with a resolution equal to that of the cropped image ? (all my JPEG images end up with the same resolution)

Welcome to the forum, Pierre-Alain

Output is determined in the export dialog:

Resolution can be set where the pink arrow points to,
Exported image size, where the green arrows point.

Please note that PhotoLab will not enlarge an image, e.g. if the specified output pixel width (or hight) exceeds what is in the cropped file.

Read more about export here: Exporter les photos - TuTo DxO