Images that are captured from the digital cameras and mobile cameras etc. contain a wealth of information such as EXIF data, image properties, geo-tagging information etc. JPEGSnoop is a small tool that has been written exclusively to read and extract this plethora of information and bring to the interested person. Digital cameras after taking the snapshots usually save them in the JPEG format, but the type of compression engine/algorithm used varies widely from one manufacturer to another, and even between the different camera models from the same manufacturer. This is also one of the reasons that final image quality of the images can vary widely between the different cameras despite having otherwise similar lens, sensor and other components on the camera. For each of the compression algorithms used by different camera manufacturer introduces certain compression pattern/signature that can be used to identify that a certain image has been captured using a specific camera. JPEGSnoop comes preloaded with a big database of compression signatures for most of the camera models on the market. An interesting use for this technology is that JPEGSnoop can process an image and try to match it’s compression signature against all the signatures in it’s stored database and if it don’t matches any then it can be assumed that the image has been modified or processed in some way. Also, if the compression signature matches Photoshop, then you can be pretty sure that the photo is no longer an original! This type of analysis is sometimes referred to as Digital Image Forensics. This information shown by the JPEGSnoop is not always accurate but in many cases give you a pretty good idea.
JPEGSnoop reports a huge amount of information, including: quantization table matrix (chrominance and luminance), chroma subsampling, estimates JPEG Quality setting, JPEG resolution settings, Huffman tables, EXIF metadata, Makernotes, RGB histograms, etc. Most of the JPEG JFIF markers are reported.
Other potential uses include: determine quality setting used in Photoshop Save As or Save for Web settings, increasing your scanner quality, locating recoverable images / videos, decoding AVI files, examining .THM files, JPEG EXIF thumbnails, extract embedded images in Adobe PDF documents, etc.
JPEGSnoop can also process and hunt for the embedded JPEG images in the following formats:
- .JPG – JPEG Still Photo
- .THM – Thumbnail for RAW Photo / Movie Files
- .AVI* – AVI Movies
- .DNG – Digital Negative RAW Photo
- .CRW, .CR2, .NEF, .ORF, .PEF – RAW Photo
- .MOV* – QuickTime Movies, QTVR (Virtual Reality / 360 Panoramic)
- .PDF – Adobe PDF Documents
JPEGSnoop is now open source and you can download it for free from here. It should work in all major versions of Microsoft Windows including Windows XP, Vista and Windows 7.
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