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What is Loss-less Rotation

After downloading images from your digital camera it is nice to rotate the images that are in portrait layout so that the top is at the top of the screen. Be careful to select software that offers 'JPEG loss-less rotation' such as Photo Explorer. If you rotate using most image editors and many other products there will be a loss of image quality after the JPEG is re-saved after the rotation. It is also possible that Exif camera information may be lost from the JPG file. Photo Explorer contains special functions that avoid loss of image quality by rotating the picture within the file and thus avoiding any loss of data.

If you open a JPEG file in a conventional image editor, rotate it, and then save it again there will some loss of image quality. This occurs when the image is re-saved to the JPEG file. No matter what setting you use to re-save the image, there will be some loss, although difficult to see and may not be visible until you open the file again. Each time you save the image will degrade a little.

The loss-less JPEG rotation used in Photo Explorer can avoid this problem as long as the rotation is 90, 180 or 270 degrees. The program re-arranges the compressed JPEG file so that the image is rotated. It does this without recompressing the data.

Note that although this works fine for digital camera pictures you may notice slight changes to the image for other JPEG files if the width and height are not a multiple of 8. A few pixels may be lost from the edge of the image. Very advanced users may also notice some rearrangement of the internal tag information in the JPEG file and other minor issues. In almost all applications this does not matter.

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