This is one of the reasons why it is extremely difficult to repair JPEG data streams. The information in the data stream is stored differentially, which means that every point in the data stream has an impact on subsequent points. The data stream in turn contains the actual picture motif. The header is tiny compared to the data stream, usually only about 0.1% of the total image file. That is, the header contains other complete JPEG files with lower resolution. Almost always the JPEG header itself contains smaller versions of the actual image. Usually, the device writes this information as EXIF.

Further, additional information such as camera settings or GPS positions are often included. It contains, so to speak, the blueprint with the help of which the picture can be built point by point. These are Huffman tables, quantization tables, and color channel definitions. The header contains information necessary to generate a valid image from the data stream. Structure of a JPEG fileĪ JPEG file is roughly made up of two parts, the header and the data stream. For this reason, repairing such a file, usually is possible with an arbitrary, undamaged file from the same device. Fortunately, 99% of all cameras and cell phones do not produce optimized JPEG files. Unfortunately, if this optimization was done on the defective file, the header can not simply be replaced by another because it has been customized for the data stream. When creating an image file, there is the option to optimize the information contained in the header. This new header must necessarily come from the same camera or the same phone.

In such a case, however, a repair can succeed if the JPEG header is completely replaced by a new header. If an image no longer contains a JPEG header, then it is not possible to display the image, at first.

Photo repair software