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如何查看ＭＡＴＬＡＢ函数的源代码

大家都知道ＭＡＴＬＡＢ是开源的，所有的函数源代码都是可以查看的。但是，对于初学者来说，可能还不知道如何查看ＭＡＴＬＡＢ函数的源代码。

函数之　　ｔｙｐｅ

假设需要查看ｆｕｎｃｔｉｏｎ＿ｎａｍｅ的源代码，在命令窗口中键入　ｔｙｐｅ　　ｆｕｎｃｔｉｏｎ＿ｎａｍｅ

即：

>> type imread

function [X, map, alpha] = imread(varargin)

%IMREAD Read image from graphics file.

%   A = IMREAD(FILENAME,FMT) reads a grayscale or color image from the file

%   specified by the string FILENAME. If the file is not in the current

%   directory, or in a directory on the MATLAB path, specify the full

%   pathname.

%

%   The text string FMT specifies the format of the file by its standard

%   file extension. For example, specify ‘gif’ for Graphics Interchange

%   Format files. To see a list of supported formats, with their file

%   extensions, use the IMFORMATS function. If IMREAD cannot find a file

%   named FILENAME, it looks for a file named FILENAME.FMT.

%

%   The return value A is an array containing the image data. If the file

%   contains a grayscale image, A is an M-by-N array. If the file contains

%   a truecolor image, A is an M-by-N-by-3 array. For TIFF files containing

%   color images that use the CMYK color space, A is an M-by-N-by-4 array.

%   See TIFF in the Format-Specific Information section for more

%   information.

%

%   The class of A depends on the bits-per-sample of the image data,

%   rounded to the next byte boundary. For example, IMREAD returns 24-bit

%   color data as an array of uint8 data because the sample size for each

%   color component is 8 bits. See the Remarks section for a discussion of

%   bitdepths, and see the Format-Specific Information section for more

%   detail about supported bitdepths and sample sizes for a particular

%   format.

%

%   [X,MAP] = IMREAD(FILENAME,FMT) reads the indexed image in FILENAME into

%   X and its associated colormap into MAP. Colormap values in the image

%   file are automatically rescaled into the range [0,1].

%

%   […] = IMREAD(FILENAME) attempts to infer the format of the file

%   from its content.

%

%   […] = IMREAD(URL,…) reads the image from an Internet URL.

%

%   Remarks

%

%   Bitdepth is the number of bits used to represent each image pixel.

%   Bitdepth is calculated by multiplying the bits-per-sample with the

%   samples-per-pixel. Thus, a format that uses 8-bits for each color

%   component (or sample) and three samples per pixel has a bitdepth of 24.

%   Sometimes the sample size associated with a bitdepth can be ambiguous:

%   does a 48-bit bitdepth represent six 8-bit samples or three 16-bit

%   samples? The following format-specific sections provide sample size

%   information to avoid this ambiguity.

%

%   Format-Specific Information (Listed Alphabetically by Format)

%

%   BMP  —  Windows Bitmap

%

%   Supported  Compression     Output

%   Bitdepths  None    RLE     Class    Notes

%   ———————————————————

%    1-bit      x        –     logical

%    4-bit      x        x     uint8

%    8-bit      x        x     uint8

%   16-bit      x        –     uint8    1 sample/pixel

%   24-bit      x        –     uint8    3 samples/pixel

%   32-bit      x        –     uint8    3 samples/pixel (1 byte padding)

%

%   CUR  — Cursor File

%

%   Supported    Compression      Output

%   Bitdepths   None Compressed   Class

%   ————————————————–

%   1-bit        x      –         logical

%   4-bit        x      –         uint8

%   8-bit        x      –         uint8

%

%   Special syntaxes:

%

%   […] = IMREAD(…,IDX) reads in one image from a multi-image icon or

%   cursor file. IDX is an integer value that specifies the order that the

%   image appears in the file. For example, if IDX is 3, IMREAD reads the

%   third image in the file. If you omit this argument, IMREAD reads the

%   first image in the file.

%

%   [A,MAP,ALPHA] = IMREAD(…) returns the AND mask for the resource,

%   which can be used to determine transparency information.  For cursor

%   files, this mask may contain the only useful data.

%

%   GIF  —  Graphics Interchange Format

%

%   Supported     Compression        Output

%   Bitdepths    None  Compressed    Class

%   ———————————————

%   1-bit         x        –         logical

%   2-to-8 bit    x        –         uint8

%

%   Special syntaxes:

%

%   […] = IMREAD(…,IDX) reads in one or more frames from a multiframe

%   (i.e., animated) GIF file. IDX must be an integer scalar or vector of

%   integer values.  For example, if IDX is 3, IMREAD reads the third image

%   in the file.  If IDX is 1:5, only the first five frames are returned.

%

%   […] = IMREAD(…,’Frames’,IDX) is the same as the syntax above except

%   that IDX can be ‘all’.  In this case, all of the frames are read and

%   returned in the order that they appear in the file.

%

%   Note: Because of the way GIF files are structured, all of the frames

%   must be read when a particular frame is requested. Consequently, it is

%   much faster to specify a vector of frames or ‘all’ for IDX than to call

%   IMREAD in a loop when reading multiple frames from the same GIF file.

%

%   HDF  —  Hierarchical Data Format

%

%   Supported   Raster image   Raster image     Output

%   Bitdepths   with colormap  without colormap Class    Notes

%   ————————————————————

%    8-bit        x               x             uint8

%   24-bit        –               x             uint8   3 samples/pixel

%

%   Special Syntaxes:

%

%   […] = IMREAD(…,REF) reads in one image from a multi-image HDF file.

%   REF is an integer value that specifies the reference number used to

%   identify the image. For example, if REF is 12, IMREAD reads the image

%   whose reference number is 12. (Note that in an HDF file the reference

%   numbers do not necessarily correspond with the order of the images in

%   the file. You can use IMFINFO to match up image order with reference

%   number.) If you omit this argument, IMREAD reads the first image in

%   the file.

%

%   ICO  — Icon File

%

%   See CUR.

%

%   JPEG  —  Joint Photographic Experts Group

%

%   Note: IMREAD can read any baseline JPEG image as well as JPEG images

%   with some commonly used extensions.

%

%   Supported    Compression      Output

%   Bitdepths   Lossy Lossless    Class      Notes

%   ——————————————————–

%    8-bit        x      x        uint8     Grayscale or RGB

%   12-bit        x      x        uint16    Grayscale

%   16-bit        –      x        uint16    Grayscale

%   36-bit        x      x        uint16    RGB(Three 12-bit samples/pixel)

%

%   JPEG 2000 – Joint Photographic Experts Group 2000

%

%   Supported      Compression      Output

%   Bitdepths     Lossy Lossless    Class

%   (per sample)

%   ———————————————————-

%    1-bit          x      x        logical

%    2- to 8-bit    x      x        uint8

%    9- to 16-bit   x      x        uint16

%

%   Note: Indexed JPEG 2000 images are not supported. Only JP2 compatible

%   color spaces are supported for JP2/JPX files. Arbitrary channels are

%   supported for raw codestream J2C files.

%

%   Special Syntaxes

%

%   […] = IMREAD(…, ‘Param1’, value1, ‘Param2’, value2, …) uses

%   parameter-value pairs to control the read operation.

%

%       Parameter name   Value

%       ————–   —–

%       ‘ReductionLevel’ A non-negative integer specifying reduction in

%                        the resolution of the image. For a reduction

%                        level ‘L’, the image resolution is reduced by a

%                        factor of 2^L. Its default value is 0 implying

%                        no reduction. The reduction level is limited by

%                        the total number of decomposition levels as

%                        provided by ‘WaveletDecompositionLevels’ field

%                        in the structure returned from IMFINFO function.

%

%       ‘PixelRegion’    {ROWS, COLS}.  IMREAD returns the sub-image

%                        specified by the boundaries in ROWS and COLS.

%                        ROWS and COLS must both be two-element vectors

%                        that denote the 1-based indices [START STOP]. If

%                        ‘ReductionLevel’ is greater than 0, then ROWS and

%                        COLS are coordinates in the reduced-sized image.

%

%       ‘V79Compatible’  A BOOL value. If true, image returned is color

%                        converted to gray-scale or RGB image as consistent

%                        with previous versions of IMREAD (MATLAB 7.9

%                        [R2009b] and earlier). Otherwise raw color

%                        image is returned. Default is false.

%

%

%   PBM  —  Portable Bitmap

%

%   Supported  Raw     ASCII (Plain)  Output

%   Bitdepths  Binary  Encoded        Class

%   —————————————-

%   1-bit        x        x          logical

%

%   PCX  —  Windows Paintbrush

%

%   Supported     Output

%   Bitdepths     Class       Notes

%   ———————————————-

%    1-bit        logical     Grayscale only

%    8-bit        uint8       Grayscale or indexed

%   24-bit        uint8       RGB (8-bit samples)

%

%   PGM  —  Portable Graymap

%

%   Supported        Raw      ASCII (Plain)  Output

%   Bitdepths        Binary   Encoded        Class

%   ————————————————

%   up to 16-bit      x            –         uint8

%   Arbitrary         –            x

%

%   PNG  —  Portable Network Graphics

%

%   Supported     Output

%   Bitdepths     Class      Notes

%   ——————————————-

%    1-bit        logical    Grayscale only

%    2-bit        uint8      Grayscale only

%    4-bit        uint8      Grayscale only

%    8-bit        uint8      Grayscale or Indexed

%   16-bit        uint16     Grayscale or Indexed

%   24-bit        uint8      RGB (Three 8-bit samples/pixel)

%   48-bit        uint16     RGB (Three 16-bit samples/pixel)

%

%   Special Syntaxes:

%

%   […] = IMREAD(…,’BackgroundColor’,BG) composites any transparent

%   pixels in the input image against the color specified in BG.  If BG is

%   ‘none’, then no compositing is performed. Otherwise, if the input image

%   is indexed, BG should be an integer in the range [1,P] where P is the

%   colormap length. If the input image is grayscale, BG should be an

%   integer in the range [0,1].  If the input image is RGB, BG should be a

%   three-element vector whose values are in the range [0,1]. The string

%   ‘BackgroundColor’ may be abbreviated.

%

%   If the ALPHA output argument is used (see below), then BG defaults to

%   ‘none’ if not specified by the user. Otherwise, if the PNG file

%   ontains a background color chunk, that color is used as the default

%   value for BG. If ALPHA is not used and the file does not contain a

%   background color chunk, then the default value for BG is 1 for indexed

%   images; 0 for grayscale images; and [0 0 0] for RGB images.

%

%   [A,MAP,ALPHA] = IMREAD(…) returns the alpha channel if one is

%   present; otherwise ALPHA is []. If ‘BackgroundColor’ is specified by

%   the user then ALPHA is []. Note that MAP may be empty if the file

%   contains a grayscale or truecolor image.

%

%   PPM  —  Portable Pixmap

%

%   Supported        Raw      ASCII (Plain)  Output

%   Bitdepths        Binary   Encoded        Class

%   ————————————————

%   up to 16-bit      x            –         uint8

%   Arbitrary         –            x

%

%   RAS  —  Sun Raster

%

%   Supported    Output

%   Bitdepths    Class     Notes

%   —————————————————-

%    1-bit       logical   Bitmap

%    8-bit       uint8     Indexed

%   24-bit       uint8     RGB (8-bit samples)

%   32-bit       uint8     RGB with Alpha (8-bit samples)

%

%   TIFF  —  Tagged Image File Format

%

%   Supported     Compression                             Output

%   Bitdepths None Packbits CCITT RGB ICCLAB CIELAB CMYK Class    Notes

%   ———————————————————————–

%    1-bit     x      x       x    –    –      –     –   logical

%    8-bit     x      x       –    –    –      –     –   uint8

%   12-bit     –      –       –    –    –      –     –   uint16  Grayscale

%                                                                or Indexed

%   16-bit     –      –       –    –    –      –     –   uint16  Grayscale

%                                                                or Indexed

%   24-bit     x      x       –    x    x      x     –   uint8   3 samples

%   32-bit     –      –       –    –    –      –     x   uint8   4 samples

%   36-bit     –      –       –    x    –      –     –   uint16  3 samples

%   48-bit     –      –       –    x    x      x     –   uint16  3 samples

%   64-bit     –      –       –    –    –      –     x   double  4 samples

%

%   NOTE: IMREAD supports 8-bit integral and 32-bit floating point tiled

%   TIFF images, with any compression and colorspace combination listed

%   above, and 32-bit IEEE floating point images.

%

%   Special Syntaxes:

%

%   A = IMREAD(…) returns color data that uses the RGB, CIELAB, ICCLAB,

%   or CMYK color spaces.  If the color image uses the CMYK color space, A

%   is an M-by-N-by-4 array.

%

%   […] = IMREAD(…, ‘Param1’, value1, ‘Param2’, value2, …) uses

%   parameter-value pairs to control the read operation.  There are three

%   different parameters you can use:

%

%       Parameter name   Value

%       ————–   —–

%       ‘Index’          A positive integer specifying which image to read in

%                        a multi-image TIFF file.  For example, if ‘Index’ is

%                        3, IMREAD reads the third image in the file.

%

%       ‘Info’           A structure array; the output of IMFINFO.  When

%                        reading images from a multi-image TIFF file, passing

%                        the output of IMFINFO as the ‘Info’ parameter helps

%                        IMREAD locate the images in the file more quickly.

%

%       ‘PixelRegion’    {ROWS, COLS}.  IMREAD returns the sub-image

%                        specified by the boundaries in ROWS and COLS.  ROWS

%                        and COLS must be either two- or three-element

%                        vectors.  If two elements are provided, they denote

%                        the 1-based indices [START STOP].  If three elements

%                        are provided, the indices [START INCREMENT STOP]

%                        allow image downsampling.

%

%   XWD  —  X Window Dump

%

%   Supported                                  Output

%   Bitdepths  ZPixmaps  XYBitmaps  XYPixmaps  Class

%   ————————————————–

%   1-bit        x          –         x        logical

%   8-bit        x          –         –        uint8

%

%   Please read the file libtiffcopyright.txt for more information.

%

%   Example:

%

%       imdata = imread(‘ngc6543a.jpg’);

%

%   See also IMFINFO, IMWRITE, IMFORMATS, FREAD, IMAGE, DOUBLE, UINT8.

%   Copyright 1984-2011 The MathWorks, Inc.

%   $Revision: 1.1.6.22.4.1 $  $Date: 2012/07/02 18:58:54 $

[filename, fmt_s, extraArgs] = parse_inputs(varargin{:});

% Download remote file.

if (strfind(filename, ‘://’))

url = true;

if (~usejava(‘jvm’))

error(message(‘MATLAB:imagesci:imread:noJava’))

end

try

filename = urlwrite(filename, tempname);

catch %#ok

error(message(‘MATLAB:imagesci:imread:readURL’, filename));

end

else

url = false;

end

if (isempty(fmt_s))

% The format was not specified explicitly.

% Verify that the file exists.

fid = fopen(filename, ‘r’);

if (fid == -1)

if ~isempty(dir(filename))

error(message(‘MATLAB:imagesci:imread:fileReadPermission’, filename));

else

error(message(‘MATLAB:imagesci:imread:fileDoesNotExist’, filename));

end

else

% File exists.  Get full filename.

filename = fopen(fid);

fclose(fid);

end

% Try to determine the file type.

[format, fmt_s] = imftype(filename);

if (isempty(format))

error(message(‘MATLAB:imagesci:imread:fileFormat’));

end

else

% The format was specified explicitly.

% Verify that the file exists.

fid = fopen(filename, ‘r’);

if (fid == -1)

% Couldn’t open using the given filename; search for a

% file with an appropriate extension.

for p = 1:length(fmt_s.ext)

fid = fopen([filename ‘.’ fmt_s.ext{p}]);

if (fid ~= -1)

% The file was found.  Don’t continue searching.

break

end

end

end

if (fid == -1)

if ~isempty(dir(filename))

error(message(‘MATLAB:imagesci:imread:fileReadPermission’, filename));

else

error(message(‘MATLAB:imagesci:imread:fileDoesNotExist’, filename));

end

else

filename = fopen(fid);

fclose(fid);

end

end

if isempty(fmt_s)

% Get format details.

fmt_s = imformats(format);

end

% Verify that a read function exists

if (isempty(fmt_s.read))

error(message(‘MATLAB:imagesci:imread:readFunctionRegistration’, fmt_s.ext{ 1 }));

end

if ((fmt_s.alpha) && (nargout == 3))

% Use the alpha channel.

[X, map, alpha] = feval(fmt_s.read, filename, extraArgs{:});

else

% Alpha channel is not requested or is not applicable.

alpha = [];

[X, map] = feval(fmt_s.read, filename, extraArgs{:});

end

% Delete temporary file from Internet download.

if (url)

delete_download(filename);

end

%————————————————————————–

function delete_download(filename)

try

delete(filename);

catch

warning(message(‘MATLAB:imagesci:imread:tempFileDelete’, filename))

end

%————————————————————————–

function [filename, fmt_s, extraArgs] = parse_inputs(varargin)

filename = ”;

fmt_s = struct([]);

extraArgs = {};

% Parse arguments based on their number.

switch(nargin)

case 0

% Not allowed.

error(message(‘MATLAB:imagesci:imread:inputParsing’));

case 1

% Filename only.

filename = varargin{1};

if ~ischar(filename)

error(message(‘MATLAB:imagesci:imread:badImageSourceDatatype’));

end

otherwise

% Filename and format or other arguments.

filename = varargin{1};

% Check whether second argument is a format.

if (ischar(varargin{2}))

fmt_s = imformats(varargin{2});

end

if (~isempty(fmt_s))

% The argument matches a format.

extraArgs = varargin(3:end);

else

% The argument begins the format-specific parameters.

extraArgs = varargin(2:end);

end

end

>>