Lossless rotate?

[YourMum]

A very simple question - is the rotate option in the XPE lossless?

I ask because I think XP's "Windows Picture and Fax Viewer" rotate option is lossy, and I want a way to rotate my digital photos properly...

[YourMum]

A very simple question - is the rotate option in the XPE lossless?

I ask because I think XP's "Windows Picture and Fax Viewer" rotate option is lossy, and I want a way to rotate my digital photos properly...

[John Rayner]

Hi YourMum,

Here is the original on the left and a bitmap copy on the right tilted a couple degrees. What do you think?

[Grafixman]

Go to this site:

http://www.impulseadventure.com/phot...-rotation.html

[John Rayner]

i can not see any difference between 0, 360 or XPE 360.

[BobInce]

All operations in XPE are lossless aren't they? They're just stored as transformations to do on-the-fly when drawing the image AFAIK. Of course if you then export as bitmap you'll be doing another encode stage so if you choose a lossy compressed format you'll lose quality then.

If you're specifically talking about rotating JPEGs at a DCT block level (avoiding recompression loss), the only program I've heard of so far that does this is betterjpeg.com.

[mckinney]

There are many programs that provide lossless rotation of JPEGs. The Independent JPEG Group keeps a list of applications that use it's code to do so at http://www.jpegclub.org/losslessapps.html. Many are free for personal use.

I believe that XPE doesn't actually save a transformed bitmap, but rather keeps the original and a list of transforms to perform. In that sense, it's lossless, but when exporting to a new JPEG losses will take place.

- Pete

[John Rayner]

I took a bitmap, rotated it 90 degrees, saved as a 100% jpg, imported it and did it again and again until I had 360 degrees (4 output/inputs)

Compared 360 created with XPE rotated and couldn;t see one difference with my vision. if interested I think I could dig up the bitmaps for you to compare...

[BobInce]

Well, okay, if you're prepared to save at 100%, losses due to recompression will be quite small! Still, it'd be nicer to be assured of no losses without making the file bigger.

Thanks for the additional apps, Peter! Now I just need to find a simple general image editor that doesn't completely suck...

[RTK]

John, it depends on the image a lot. Both in terms of content (fine detail and subtle graditations(sp?) as shadows). Physical size also matters... Resampling any image over and over again will degrade the quality. Many silly artifacts will also only show up when you print an image.

Andrew also has a point with his 100%...