SLAMorris Final Thesis After Corrections.pdf - Cranfield University

Figure 9-7: Reassembling an image by trying every permutation
The production of all syntactically valid image fragment sequences provides an
analyst with the opportunity to decide how to proceed. Therefore unless a valid
image fragment sequence directly follows a subrecord header fragment the
method will produce and store the visual thumbnails for any valid JPEG
sequence which can be formed from the remaining fragments. In order to
validate the images each set of fragments was passed to a python program
which ran an Image module and attempted to verify and open the images. If the
entire image appeared to be a valid sequence the image was exported and put
in the same directory as the rest of the reassembled file. If multiple fragment
sequences were valid for a subrecord the image only sections of the subrecord
were left blank and the valid image sequences were stored in a sub-directory
named with the reassembled files name and relative offset of the subrecord.
The log for reassembling images shows the original name of each image only
fragment and its position in the completed sequence.
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