Width extraction of JPEG fragment via frequency coefficients scale similarity measuring

The size field in encoded JPEG file header is very important to the image displaying, so it should be designated to avoid the problem of confusedly displaying. The current measure of constructing of a pseudo header does not deal with this issue very well. To address this problem, the paper presents an algorithm which uses luminance-DC-frequency-coefficients-scale differential algorithm to obtain the width of a header-missing JPEG fragment without using any original meta-data. We use both the algorithm and the construction of decipher prerequisites to get the value. The results of experiments have shown that they can obtain the width information and the location of 8*8 blocks sequence of header-missing JPEG fragment with resilience and accuracy.