www.pudn.com > balloonSnake(matlab).rar > rawread.m

function [X,map] = rawread(filename,n,m); 
% RAWREAD Read a Portable Bitmap file, or a raw file. 
%       RAWREAD('imagefile.raw', xsize, ysize) reads a "raw" image file 
%       RAWREAD('imagefile.pgm') reads a "pgm" (portable gray map) image 
%       [X,map] = RAWREAD('imagefile.raw') returns both the image and a 
%       color map, so that 
%               [X,map] = rawread('imagefile.raw',sx,sy); 
%       or      [X,map] = rawread('imagefile.pgm'); 
%               image(X) 
%               colormap(map) 
%       will display the result with the proper colors. 
% 
%       NOTE : map is optional and could be replaced during the display by 
%              the "colormap('gray')" command 
% 
%       See also IMWRITE, IMREAD, IMAGE, COLORMAP. 
 
dot = max(find(filename == '.')); 
suffix = filename(dot+1:dot+3); 
 
if strcmp(suffix,'pgm') | strcmp(suffix,'raw') 
 
   disp(sprintf('\nopens %s file\n',filename)); 
   fp = fopen(filename,'rb','b');  % "Big-endian" byte order. 
    
   if (fp<0) 
      error(['Cannot open ' filename '.']); 
  end 
 
   if strcmp(suffix,'pgm') 
   % Read and crack the header 
    
      head = fread(fp,2,'uchar'); % pgm magic number : P5 
      if ~strcmp(head,'P5'), 
         fprintf(1,'\n Magic Number : %s\n',head); 
      else 
         fprintf(1,'\n Bad Magic Number : %s\n',head); 
         error('cannot continue this way, good bye cruel world'); 
      end 
 
      c = fread(fp,1,'uchar'); %reads the carriage return separating P5 from the creator 
 
      precreator = fread(fp,1,'uchar'); % look for a '#' character preceeding a creator signature 
      if precreator == '#', 
         c = setstr(20);  % any character except carriage return 
         cr = setstr(10); % defines a carriage return 
         while c ~= cr, 
               c = fread(fp,1,'uchar'); 
               creator = [creator,c]; 
         end; 
         fprintf(1,'\n creator : %s\n',creator); 
      else 
         fprintf('\n No creator signature\n'); 
         fseek(fp,-1,'cof'); % return one char before 
      end; 
 
end 
 
   if nargin <2, 
      if strcmp(suffix,'raw') 
      % assume image size is 256x256 
         disp('RAW file without size : assume image size is 256x256'); 
         n = 256; 
         m = 256; 
      else % for PGM files 
      % reads the size and depth 
          disp(' reads sizes'); 
          n = fscanf(fp,'%d',1); 
          tn = num2str(n); 
          disp(['  xsize = ' tn]); 
          m = fscanf(fp,'%d',1); 
          tm = num2str(m); 
          disp(['  ysize = ' tm]); 
          p = fscanf(fp,'%d',1); 
          tp = num2str(p); 
          disp(['  depth = ' tp]); 
          c = fread(fp,1,'uchar'); %reads the last carriage return 
      end; 
   end 
 
 
   % Creates a gray palette and scale it to [0,1]. 
   disp(' create gray palette'); 
   for i=1:256, 
       map(i,[1:3])=[i/256,i/256,i/256]; 
   end; 
    
   
   % Read the image 
   disp(' Reads image data ...'); 
   [X,l] = fread(fp,[n,m],'uchar'); 
   if l ~= m*n, l, error('HSI image file is wrong length'), end 
   % Image elements are colormap indices, so start at 1. 
   X = X'+1; 
    
   fclose(fp); 
   
   disp('end'); 
 
else 
   error('Image file name must end in ''raw'' or ''pgm''.') 
end