下面的程序代码相当规范,不是我写的,记得好像是在MATLAB网站的交流区下载的。
每个*.img文件对应一个*.hdr的头文件,程序首先从头文件里得到影像的行列和波段数,然后按照二进制方式读取,并按照行列波段数重排为多维矩阵。
function [image,p,t]=freadenvi(fname);
% freadenvi - read envi image (V. Guissard, Apr 29 2004)
%
% Reads an image of ENVI standard type
% to a [col x line x band] MATLAB array
% image=freadenvi(fname)
% [image,p]=freadenvi(fname)
% [image,p,t]=freadenvi(fname)
%
% INPUT :
%
% fname string giving the full pathname of the ENVI image to read.
%
% OUTPUT :
%
% image----------- c by l by b array containing the ENVI image values organised in
% c : cols, l : lines and b : bands.
% p 1 by 3 vector that contains (1) the nb of cols, (2) the number.
% of lines and (3) the number of bands of the opened image.
%
% t string describing the image data type string in MATLAB conventions.
%
% NOTE : freadenvi needs the corresponding image header file generated
% automatically by ENVI. The ENVI header file must have the same name
% as the ENVI image file + the '.hdf' exention.
%
%%%%%%%%%%%%%
% Parameters initialization
elements={'samples ' 'lines ' 'bands ' 'data type '};
d={'bit8' 'int16' 'int32' 'float32' 'float64' 'uint16' 'uint32' 'int64' 'uint64'};
% Check user input
if ~ischar(fname)
error('fname should be a char string');
end
% Open ENVI header file to retreive s, l, b & d variables
rfid = fopen(strcat(fname,'.hdr'),'r');
% Check if the header file is correctely open
if rfid == -1
error('Input header file does not exist');
end;
% Read ENVI image header file and get p(1) : nb samples,
% p(2) : nb lines, p(3) : nb bands and t : data type
while 1
tline = fgetl(rfid);
if ~ischar(tline), break, end
[first,second]=strtok(tline,'=');
switch first
case elements(1)
[f,s]=strtok(second);
p(1)=str2num(s);
case elements(2)
[f,s]=strtok(second);
p(2)=str2num(s);
case elements(3)
[f,s]=strtok(second);
p(3)=str2num(s);
case elements(4)
[f,s]=strtok(second);
t=str2num(s);
switch t
case 1
t=d(1);
case 2
t=d(2);
case 3
t=d(3);
case 4
t=d(4);
case 5
t=d(5);
case 12
t=d(6);
case 13
t=d(7);
case 14
t=d(8);
case 15
t=d(9);
otherwise
error('Unknown image data type');
end
end
end
fclose(rfid);
t=t{1,1};
% Open the ENVI image and store it in the 'image' MATLAB array
disp([('Opening '),(num2str(p(1))),('cols x '),(num2str(p(2))),('lines x '),(num2str(p(3))),('bands')]);
disp([('of type '), (t), (' image...')]);
fid=fopen(fname);
image=fread(fid,t);
image=reshape(image,[p(1),p(2),p(3)]);
fclose(fid);