image editingpreview
When I use Preview.app to rotate a .TIFF image file 90 degrees, the resulting file is about 10% to 20% larger. All I do is open, rotate, save; there is no exporting or "save as" changes. I've tried this on multiple TIFF files and the behavior is constant.
It's the same file with the same data, so why the size increase?
(2013 rMBP) — (OS X 10.11.4)
This works for me on Mountain Lion:
Open all the JPG's in Preview so that the files are selectable within the one window, i.e. thumbnails of the JPG's are viewable in the selection pane located the window's left side.
Click in the selection pane and select all the thumbnails with Cmd-A.
Select File > Print... from the menu bar.
Select PDF > (from the drop down) Save as PDF... from within the Print Dialog.
Take it from there...
This seems to be a bug in Preview. There's a related thread about this topic in which many people say they are experiencing the same problem. I too have just tested it out and see the same results.
There are 2 workarounds I can think of. The 1st is to select all the annotations and set their color manually:
The 2nd workaround is to use the Python script from the same thread previously mentioned.
Best Answer
So when you make any changes to a file and 'save' it in Preview, the file is re-encoded. It must be using different settings that the program that originally created it.
It has nothing to do with rotating. If it did you could try rotating it back and the file size would drop, but that's not the case.
I just tried saving a TIF and I can see that Preview seems to be adding an Alpha channel to the image. Not sure if that would be the reason for the increase, but it is something that is different.