While using the Batch Image Rotate / Flip Images tool, I can specify to perform a lossless rotate on jpeg files by selecting the Options button and checking the Force Lossless JPEG Operations box. This is great.

I want to know if a lossless rotation is also performed when I select a thumbnail in the file list pane and rotate it by using the Rotate Left tool in the Context Sensitive Toolbar.

Can anyone help me with this?

Thanks, Greg

I have a related question. I just tried the rotate and had lossless activated. Even so, the file size is changed. Going from the original orientation at 2,028kb, to rotated once to the right at 1,936 kb, to rotated twice to the right 1,944 kb, to rotated again to the right 1,936 kb, to fourth time (and thereby back to original orientation) at 1,944 kb. Where is the last 100 kb, and why is the size different?

thanks
Niels

As far as I know this is perfectly OK.

JPEG consists of raw image data, lossy processed and losslessly compressed, and a number of headers.
When rotating, compression method and headers can be changed without affecting image data (ie. what you see).
If you want to be 100% sure, take an image, rotate it and then rotate back, load into image editor and perform mathematical subtraction on original and rotated image both ways (original-rotated and rotated-original). If in both cases you get solid black image, that means the rotations don't changed a bit of original.

X.

As I have not tried to make a subtraction before, how do I do that? I have ACDsee 9 and Photoshop 7 available.

thanks
Niels