JPEG Toolbox
The Matlab’s built-in functions used to handle digital images provide only basic conversion between the given JPEG file and image pixels. Thus, they are not effective in dealing with a DCT-based steganographic method since there is no access to the qDCT coefficients. To overcome this issue, we use a dedicated Matlab JPEG Toolbox developed by Phil Sallee. The Sallee’s Toolbox contains special functions allowing to access and manipulate the qDCT coefficients of a given JPEG file.
The main two functions in the package of Sallee “jpeg_read” and “jpeg_write” perform the steps of the lossless compression applied to the qDCT coefficients, including Huffman coding and decoding. Thus, they provide more functionality, since they give the ability to gain direct access to all the structural elements of a JPEG file from Matlab, including the matrices of qDCT coefficients and the quantization tables.
Downloads of Phil Sallee’s MATLAB JPEG Toolbox:
1 - This package is the original one; jpegtbx_1.4.zip. It includes several functions for handling jpeg matrices, including the two main functions for reading and writing jpeg files. In addition to Matlab functions (m files), the package includes pre-compiled MEX binaries files (.dll) working under a 32-bit system for Windows.
Phil Sallee’s ORIGINAL Toolbox
2 - This package is based on the original one and provided by the Digital Data Embedding Laboratory at Binghamton University in New York. It includes pre-compiled MEX binaries for 32-bit and 64-bit systems for several operating systems.