Analyze JPEG Error Level using Image Forensics Techniques
February 28, 2010 | Filed under Imaging;
Whenever you resave a JPEG image, it actually loses quality. For example, if you have a JPG image that has 90% quality and you resave it again at 90% quality, you will end up with an image at 81% quality. The quality doesn’t gets maintained except it kept on dropping. Logically to know if the image has been resaved multiple times or tampered with is nearly impossible. Thanks to Error level analysis, it can help you work out if a photo has been digitally altered. Error level analysis allows you see to see the difference in quality level, represented by brightness. Things which are very bright have been edited most recently, whilst duller parts have been resaved multiple times. This allows you to see not just which parts of the image have been changed, but in what order the changes occurred.
It is easy to use Error Level Analysis. You will only need to specify a direct link to the image, click a button and the JPEG image will be processed. The only con about this free service is the quality of the JPEG image to be processed has to be really good. If a picture has been resaved many times, or if a picture is of a very low jpeg quality, it is quite difficult to determine accurately whether it has been digitally altered. Likewise, if all parts of a picture have been saved the same amount of times, it will not pick up either. It did not mention if there is a size restriction on the image it can process.
Click HERE to visit Error Level Analysis official website to have your JPEG image analyzed if it has been tampered with.