Improve preview overlay usability

Add small rectangles at the corners of the preview overlay. This makes it
easier to place the edges of the cropping area on black borders or lines.

diff --git a/pdfstitch b/pdfstitch
index 2fec2272ea3135b2baa00c97486596e9b832d699..a754d0ad60ff02c7eeb7659f51ccc8b067e13c82 100755 (executable)
--- a/pdfstitch
+++ b/pdfstitch
@@ -160,6 +160,10 @@ else
                 my $previewcontent = $previewpage->gfx();
                 $previewcontent->egstate($transparency);
                 $previewcontent->rect($llx, $lly, $urx, $ury);
+                $previewcontent->rect($llx - 20, $lly + $ury, 20, 20); # upper left
+                $previewcontent->rect($llx + $urx, $lly + $ury, 20, 20); # upper right
+                $previewcontent->rect($llx - 20, $lly - 20, 20, 20); # lower left
+                $previewcontent->rect($llx + $urx, $lly - 20, 20, 20); # lower right
                 $previewcontent->fillcolor('%F000');
                 $previewcontent->fill();
             }