Reported v4.23: Obscure Error Msg JPEG Lossless image Crop

[pixperson]

JPEG Lossless Image Crop

Obscure / uninformative error message
when
* option Properties/Settings for JPG/PCD/GIF
is set to "AutoRotate images according to EXIF"
and
* attempt to use the JPG Lossless Crop plugin
* image has been auto-rotated

produces error message
"JPG Crop Error -1"

because the crop window is based on the rotated image

Since there is a JPG Lossless Rotation plugin,
the software should automatically handle this situation, by
first doing a Lossless Rotation
then doing the Lossless crop.

But if it can't, at least provide an informative error
message that tells users what is the problem

Overall, IRFANVIEW is a GREAT program, very helpful!

Thank you

[Mij]

Yes, what you report is correct and some action should be taken to prevent users experiencing this problem. I do not like your suggested solution though. It should not be necessary to force a user to perform a lossless rotation just to be able to use lossless crop.

There is more than one issue here. First is an unfortunate but unavoidable result of having an Auto-rotate feature. If the image has been rotated upright by Auto-rotate, then the picture you see is not as it is stored in the file. Lossless operations are performed directly on the file contents without regard to how it is being shown on screen. That already catches out many using the lossless rotate feature. They request a 90 deg rotation and are taken aback when the displayed image either rotates 180 deg or does not change at all. That needs to be addressed at the very least by a warning, if lossless operations are selected, that Auto-rotate is On and may cause unexpected results.

I doubt that a warning is enough for lossless crop though. There is a further issue in that the selection box coordinates are (apparently) held internally relative to the window, not relative to the image itself. What you see displayed are calculated coordinates dependent on the displayed zoom and scroll position of the image within the window. One consequence is what you have discovered, that the figures passed to Lossless crop can be complete nonsense, but again there are other consequences that affect other users who have posted on this forum. MItaly reports that he does use true image coordinates in the IrfanPaint plugin, and if Irfan could be persuaded to do the same in the core program then I suspect it would prove easier to pass correct coordinates to Lossless crop when Auto rotate is On.

One "solution" is to gray out the Lossless features in the menu when Auto-rotate is On. I would not vote for that. IMHO these issues badly need to be addressed and solved once and for all.