no bug Thumbnails / Lossless operations

[flatman]

Irfanview 4.60 32bit with Jpg_trans.dll 4.59.0.0 on a Win 10.
When using in "Irfan View Thumbnails" the feature "JPG Lossless Operations" / "Rotate" (either direction, left or right), the selected pictures (a single or multiple selected) is/are rotated by 180°, or not at all, and not only (as intended) by 90°. This happens also when I apply this operation on to a single opened picture (Options / JPG Lossless Rotation (Plug-In).
Only on the second attempt with the same (still selected) pictures to the other direction brings then the intended rotation by 90°.

This strange behaviour can only be observed for the first operation Irfanview does to the file (e.g. Rotation to in specified direction, or Auto-Rotation according to EXIF-information of the picture) - after that, the feature works as it should. So I guess that there is something wrong with the pictures, and not necessarily with the program. Nevertheless, Unfortunately, I cannot include one of the pictures I received where I noticed this behaviour due to upload restrictions (the picture is 3864 x 5152).

Best regards
Wolfgang

[Bhikkhu Pesala]

What is checked in Settings, JPG, Autorotate image according to EXIF info (if available)?

Upload the file to filebin.net (see my forum signature).

[flatman]

Thank you for your reply!
In Options -> Properties/Settings -> JPG/PCD/GIF -> JPEG - Load, there is only "Auto-rotate image according to EXIIF info (if available)" checked.

These pictures were taken with very high resolution (20Mpixel), resulting in a 4,2MB file. Uploading was not possible, resulted in a "Insufficient storage (4.2MB)"-error form filebin.net.

Another thing I think is strange is the fact that after the first JPG lossless operation, the file size on my hard disc decreases from 4,17MB (for one particular file) down to 3,82MB - but even without saving the file! Seems like Irfanview automatically rewrites the file without being asked to do so...
At least this observation explains to my why I was not able to reproduce the behaviour by "File -> Reopen" (Shift + R), after I had applied a Lossless JPG operation: The file I reloaded was not the "original" file I loaded the first time...

Best regards
Wolfgang

[Bhikkhu Pesala]

Look at the dialog. You agreed to rewrite the file.

If Filebin is busy, you could use other resources, or Dropbox. I recommend Filebin because no registration is required. I guess that being free and no hassle means it is going to be popular. I don't know how they make their money.

[JendaLinda]

You don't need to worry about the decreasing file size. It has no effect on the image quality. Lossless operations can optionally remove metadata (see the bottom of the dialog). They also rearrange the contents of JPG files and save them more efficiently.

[flatman]

Pesala: Thank you so much, you opened my eyes ;-) ! Today I was able to upload to filebin.net, the file can be found at https://filebin.net/cnqlhyv3i2nav202.

Pesala and @Linda: So do I understand correctly that the camera does a bad job by adding unnessesary data to the file? And maybe writes (parts?) of the file in an incorrect way that is corrected the first time Irfanview does a lossless operation and rewrites the file?
That would explain the strange behaviour.

To solve this, I'd have to select all the pictures I received that were taken with that particular camera (in the thumbnail view), apply a lossless operation (for instance, "None" combined with "Rebuild EXIF thumb" and "Optimize JPG file", and then apply the desired transformation afterwards.
Did I understand correctly?

Best regards
Wolfgang

[Bhikkhu Pesala]

If I disable Autorotate image according to EXIF info (if available) the image is rotated by 90° as expected.

If I enable the setting, the image is not rotated on screen, as it is already in the correct orientation (Top Left).