WTF is wrong with rotating a JPG from a camera?!?
I open an image in preview, rotate it 90 degrees, save it back.
Upload it.
Its not rotated at all! Did I mess up? A quick check verifies that the image is, in fact, apparently rotated on the mac. But, yet, somehow, it is not rotated.
What the fuck is going on here?!?
UPDATE: The problem:
"Preview" merely changes the EXIF data JPEG header to indicate that the image should be rotated by whatever opens the image next.
I discovered this when opening one of the "rotated" images using GIMP.
This would be commendable if "Preview" were using this method to perform a totally lossless rotation, however, it is not. A 2592x1944 JPG from a Sony T33 camera that once took 1,574,595 bytes on disk takes only 758,550 bytes on disk after "rotation".
My question is, if the JPEG is going to be recompressed anyways, why not just perform the actual rotation? The method used would have been a clever, quality preserving idea if it altered only the EXIF data, but thats not whats going on here.
Upload it.
Its not rotated at all! Did I mess up? A quick check verifies that the image is, in fact, apparently rotated on the mac. But, yet, somehow, it is not rotated.
What the fuck is going on here?!?
UPDATE: The problem:
"Preview" merely changes the EXIF data JPEG header to indicate that the image should be rotated by whatever opens the image next.
I discovered this when opening one of the "rotated" images using GIMP.
This would be commendable if "Preview" were using this method to perform a totally lossless rotation, however, it is not. A 2592x1944 JPG from a Sony T33 camera that once took 1,574,595 bytes on disk takes only 758,550 bytes on disk after "rotation".
My question is, if the JPEG is going to be recompressed anyways, why not just perform the actual rotation? The method used would have been a clever, quality preserving idea if it altered only the EXIF data, but thats not whats going on here.