JPEGsnoop allows for detailed examination of the EXIF and ITPC data contained in digital photos, AVI files, PDF documents and several other file formats. The program reports an extensive amount of information, including quantization table matrix, chroma subsampling, estimated JPEG Quality setting, JPEG resolution settings, Huffman tables, Makernotes, RGB histograms and much more. It can be used to review camera settings, to determine whether an images has been edited or tampered with and also to detect errors in corrupted files and several other advanced uses. Other features include the ability to extract embedded thumbnail images, full AVI file parsing, multi-channel preview, an integrated database of thousands of compression signatures and more.

Every digital photo contains a wealth of hidden information -- JPEGsnoop was written to expose these details to those who are curious.
Not only can one determine the various settings that were used in the digital camera in taking the photo (EXIF metadata, IPTC), but one can also extract information that indicates the quality and nature of the JPEG image compression used by the camera in saving the file. Each digical cameras specifies a compression quality levels, many of them wildly different, leading to the fact that some cameras produce far better JPEG images than others.

One of the latest features in JPEGsnoop is an internal database that compares an image against a large number of compression signatures. JPEGsnoop reports what digital camera or software was likely used to generate the image. This is extremely useful in determining whether or not a photo has been edited / tampered in any way. 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 Ballistics / Forensics.
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. In addition, you can enable a full huffman VLC decode, which will help those who are learning about JPEG compression and those who are writing a JPEG decoder.
Other potential uses: 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 will open and attempt to decode any file that contains an embedded JPEG image, such as:
.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)

Recent Features:
* XMP APP1 & ICC Header display
* GPS EXIF metadata display
* Full detailed Huffman VLC decoding output for those interested in writing a decoder or learning JPEG compression
* Automatic display of YCC DC block values (16-bit)
* MCU Grid overlay and automatic display of mouse MCU position and file offset in image display window.
* Test overlay function enhanced to allow quick apply and binary code readout.
* Image zoom level from 12.5% - 800%.
* Extract embedded JPEGs -- can be used to extract thumbnails, hidden JPEG files, as well as frames from Motion JPEG AVI files.
* Compression detection enhanced to detect rotated signatures, comment field.
* Full AVI file parsing (to identify MotionJPEG)
* DQT table searches in Executables (for "hackers")
* Detect edited images or identify original digital camera that took a photo!
* Integrated database of thousands of compression signatures (image fingerprint) for digital cameras and editing software
* File overlay test function
* Multi-channel preview: RGB, YCC, R/G/B, Y/Cb/Cr
* Pixel position lookup into file offset
* Examine Motion JPEG .AVI or .MOV (Quicktime) files (MJPG or MJPEG) and play through!
* Examine any file fragments that may contain a JPEG image
* YCC to RGB Color correction / clipping statistics reports
* Command-line execution
* Huffman variable-length code statistics
* Expansion of DHT (Huffman Table Expansion into bitstrings)
* Determine IJG JPEG Quality factor

The license of this software is Freeware, you can free download and free use this image utility software.