www.pudn.com > ofdm_matlab.rar > bmpread.m

function [X,map,out3]=bmpread(filename);  
%BMPREAD Read a BMP (Microsoft Windows Bitmap) file from disk.  
%	[X,MAP]=BMPREAD('filename') reads the file 'filename' and  
%	returns the indexed image X and associated colormap  
%	MAP. If no extension is given for the filename, the  
%	extension '.bmp' is assumed.  
%	[R,G,B]=BMPREAD('filename') reads the 24-bit BMP file  
%	from the file 'filename'.  
%	BPP=BMPREAD('filename') returns the number of bits per  
%	pixel in the BMP file.  
%  
%	BMPREAD does not read 1-bit or compressed BMP files.  
%  
%	See also: BMPWRITE, GIFREAD, HDFREAD, PCXREAD, TIFFREAD,  
%	          XWDREAD.  
  
%	Mounil Patel 3/10/94  
%	Revised Steve Eddins February 9, 1995  
%	Copyright (c) 1994 by The MathWorks, Inc.  
%	$Revision: 1.14 $  $Date: 1996/06/14 12:39:07 $  
  
  
if (nargin~=1)  
	error('Requires a filename as an argument.');  
end;  
  
if (isstr(filename)~=1)  
	error('Requires a string filename as an argument.');  
end;  
  
if (isempty(findstr(filename,'.'))==1)  
	filename=[filename,'.bmp'];  
end;  
  
fid=fopen(filename,'rb','l');  
if (fid==-1)  
	error(['Error opening ',filename,' for input.']);  
end;  
  
bfType=fread(fid,2,'uchar');  
if (bfType~=[66;77])  
	fclose(fid);  
	error('Not a BMP file.');  
end;  
  
bfSize=fread(fid,1,'uint');  
bfReserved1=fread(fid,1,'ushort');  
bfReserved2=fread(fid,1,'ushort');  
bfOffBytes=fread(fid,1,'uint');  
  
biSize=fread(fid,1,'uint');  
if (biSize~=40)  
	fclose(fid);  
	error('Not a MS Windows Device Independent Bitmap BMP file.');  
end;  
  
biWidth=fread(fid,1,'uint');  
biHeight=fread(fid,1,'uint');  
biPlanes=fread(fid,1,'ushort');  
biBitCount=fread(fid,1,'ushort');  
if (biBitCount == 1)  
  error('BMPREAD does not read 1-bit BMP files.');  
end  
biCompression=fread(fid,1,'uint');  
if biCompression~=0   
	error('Can''t load compressed format bitmaps.');  
end;  
biSizeImage=fread(fid,1,'uint');  
biXPels=fread(fid,1,'uint');  
biYPels=fread(fid,1,'uint');  
biClrUsed=fread(fid,1,'uint');  
biClrImportant=fread(fid,1,'uint');  
  
if (nargout <= 1)  
  X = biBitCount;  
  map = [];  
  fclose(fid);  
  return;  
end  
  
if ((nargout == 2) & (biBitCount == 24))  
  error('Three output arguments required for 24-bit BMP file.');  
end  
  
if ((nargout == 3) & (biBitCount < 24))  
  error('Only two arguments needed for 4- and 8-bit BMP files.');  
end  
  
if (biBitCount == 24)  
  if (rem(biWidth,4)~=0)  
    XSize=biWidth+(4-rem(biWidth,4));  
  else  
    XSize=biWidth;  
  end  
  YSize=biHeight;  
  Size=XSize*YSize;  
  
  fseek(fid, bfOffBytes, 'bof');  
  X=fread(fid,Size*3,'uchar');  
  out3 = rot90(reshape(X(1:3:length(X)), XSize, YSize)) * (1/255);  
  map = rot90(reshape(X(2:3:length(X)), XSize, YSize)) * (1/255);  
  X = rot90(reshape(X(3:3:length(X)), XSize, YSize)) * (1/255);  
  if (rem(biWidth,4)~=0)  
    X=X(:,1:biWidth);  
    map = map(:,1:biWidth);  
    out3 = out3(:,1:biWidth);  
  end;  
    
  fclose(fid);  
  return;  
end    
  
if (biClrUsed==0)  
	nColors=2.^biBitCount;  
else  
	nColors=biClrUsed;  
end;  
  
% load color map now  
if (biClrUsed>256)  
	map=[];	% 24-bit images have no colormap  
else  
	map=fread(fid,4*nColors,'uchar');  
	map=reshape(map,4,nColors);  
	map=map';  
	map=map(:,1:3);  
	map=fliplr(map);  
end;  
  
map=map./255;  
  
% read in 8-bit image data  
if (biBitCount==8)  
	if (rem(biWidth,4)~=0)  
		XSize=biWidth+(4-rem(biWidth,4));  
	else  
		XSize=biWidth;  
	end  
	YSize=biHeight;  
	Size=XSize*YSize;  
  
	fseek(fid, bfOffBytes, 'bof');  
	X=fread(fid,Size,'uchar');  
	X=reshape(X,XSize,YSize);  
	X=rot90(X);  
	X=X+1;  
	if (rem(biWidth,4)~=0)  
		X=X(:,1:biWidth);  
	end;  
end;  
  
if (biBitCount==4)  
	XSize=ceil(biWidth/2);  
	if (rem(XSize,4)~=0)  
		XSize=XSize+rem(XSize,4);  
	end;  
	YSize=biHeight;  
	Size=XSize*YSize;  
	fseek(fid, bfOffBytes, 'bof');  
	X=fread(fid,Size,'uchar');  
	X=reshape(X,XSize,YSize);  
	X=X';  
	loX=X;  
  
	index=loX>127;  
	loX(index)=loX(index)-128;  
	index=loX>63;  
	loX(index)=loX(index)-64;  
	index=loX>31;  
	loX(index)=loX(index)-32;  
	index=loX>15;  
	loX(index)=loX(index)-16;  
  
	X=X-loX;  
	X=X./16;  
	[m,n]=size(X);  
	X(:,1:2:(n*2))=X;  
	X(:,2:2:(n*2))=loX;  
	X=flipud(X);  
	X=X+1;  
end;  
  
cmax=max(max(X));  
map=map(1:cmax,:);  
  
fclose(fid);