After coming back from our honeymoon, me and my wife has been going through the photos that we took numerous times. We just miss all the beautiful scenery and building architecture. At first my wife would just go through herself and then I’d join her when I am done checking the forums. I noticed that all the photos were properly rotated even though I’ve taken many photos with the camera in vertical position. She told me that whenever she rotates the photo and then go to the next photo, she will see a small “Saving” message. Then the next time she opens the image, it will stay at the same rotated position.

I immediately stopped her from continue doing that because I remembered when I was using Windows XP, when I rotate and go to the next photo, I get a warning message that says “Because of the dimensions of this picture, rotating it might permanently reduce its quality. Rotating a picture automatically saves it using the original name. To save a backup copy first, see ‘Copy an image’ in Help. Do you want to proceed?”.
JPEG lossless rotation
I wasn’t really sure at first so I did a test to see if rotating pictures with the built-in photo viewer in Windows will cause any quality loss.

I used a photo that is originally 1MB in size. After rotating 90degrees and closing the image, the file size became 957KB. I tried rotating it back to the original position and file size changes to 969KB. To verify if there are any difference, I used ImageMagick’s compare tool and indeed there were quality loss.

After doing more research on JPEG format, I found out that JPEG file format supports compression, which reduces image size while keeping the image acceptable to the human eye. Unfortunately, to compress images well, the algorithm intentionally loses information. What is saved is NOT the same image as what is in memory; the color of a particular pixel or area of an image will generally will NOT be exactly the same color that was saved. This is particularly true near the edges of objects within the image. Normally this lossy nature of JPEG is not very noticeable. However it can become noticeable when you either load and save a JPEG image multiple times or use a very low quality with a diagram showing sharp color changes.

Now, STOP using Windows XP’s Picture and Fax Viewer, Windows Vista’s Photo Gallery Viewer or Windows 7’s Photo Viewer to rotate your precious digital photos! Once the quality is loss, you can NEVER get it back.

For rotating a JPEG picture without quality loss, you can use any of the programs in this list. There are a total of 81 softwares for you to choose from. One of my personal favorite is called JPEG Lossless Rotator. It is constantly being updated and also free for private non-commercial or educational use, including non-profit organization.

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