As far as I know, you can only insert text or another image with Irfan. Click and drag a box about the size of what you want to insert, then under Edit, Insert text into selection (or, Ctrl+T), create an arrow and text if desired. It's a bit tricky at first, but eventually you'll get the hang of it. You can also open another image and draw a box around part of what you would like to insert, then click the scissors to cut it. Go to the original image, draw a box where you would like the segment to be, then click Paste. The cut part will fit into the box no matter what the shape or size you drew.
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