Rotate an image without re-encoding?

[atamo]

It is possible to rotate an image e.g. jpg without re-encoding?
I know how rotate it but how save it without re-encoding?

[Bhikkhu Pesala]

Look at lossless JPG rotation.

[atamo]

nice plugin but I want to rotate with custom (45 grade) , not with fixed size

[jazzman]

It's in the very nature of the JPEG compression algorithm that this is not possible. Only multiples of 90 degrees will work.

See here if you want to go into the technical details: http://www.impulseadventure.com/phot...mpression.html

PS: Besides, every rotation other than multiples of 90 degrees requires interpolation and therefore a change that even at best will slightly degrade image quality.

[atamo]

thank's for help and the link

I found another way: Exif Orientation Tag

[Jacal]

The exif tag is the most nonintrusive way to rotate a jpeg, all recent software should support it, but, again, only 90 degree steps are supported. (If I'm not very wrong.)