jpegtbx1.4

This distribution contains routines for manipulating files formatted according to the Joint Photographic Experts Group (JPEG) standard. Matlab's built-in IMREAD and IMWRITE functions provide basic conversion between JPEG files and image arrays. The routines in this package provide additional functionality for directly accessing the contents of JPEG files from Matlab, including the Discrete Cosine Transform (DCT) coefficients, quantization tables, Huffman coding tables, color space information, and comment markers. It is assumed that the user of this software has a good understanding of both the JPEG compression standard and Matlab data structures. This software is based in part on the work of the Independent JPEG Group (IJG), as it makes use of IJG's free JPEG code library. If the MEX file binaries provided in this distribution are not the ones you need for your system, you will need to download IJG's code library and install it on your system before compiling the source code. See "Installing" for more details. ---- Phil Sallee 9/2003

% BDCT Blocked discrete cosine transform
%
%    B = BDCT（A） computes DCT2 transform of A in 8x8 blocks.  B is
%    the same size as A and contains the cosine transform coefficients for
%    each block.  This transform can be inverted using IBDCT.
%
%    B = BDCT（AN） computes DCT2 transform of A in blocks of size NxN.

% Phil Sallee 9/03

function b = bdct（an）

if （nargin < 2）
  n = 8;
end

% generate the matrix for the full 2D DCT transform （both directions）
dctm = bdctmtx（n）;

% reshape image into blocks multiply and reshape back
[vrc] = im2vec（an）;
b = vec2im（dctm*v0nrc）;

 属性            大小     日期    时间   名称
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     文件      65536  2003-10-30 18:44  jpeg_read.dll

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                65536                    1