fopen gives -1. How to open??

Question

Brenden 2012-6-28

0
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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/42271-fopen-gives-1-how-to-open

My current work involves image processing. Just recently I have been looking at archived files from the early 2000's. The problem is that these images are stored as *.FILT, *.filt or *.im.... To my knowledge these filetypes where created by a past colleague inorder to save the image data with a text header (information about the image). My problem now is that these images cannot be opened as the software is far out of date.

I have written a small code to convert these files into *.bmp as follows:

clear all 
close all
% Prompt for image file 
[image_file image_file_path image_file_filterindex] = uigetfile({'*.FILT;*.filt;*.im;*'}, 'Select image for conversion to *.bmp','MultiSelect','On');
if iscell(image_file) ==1
    for n=1:length(image_file)
        [pathstr, name, ext] = fileparts(image_file{n});
        file_id = fopen(image_file{n})
        if file_id ~= -1
            header = fread(file_id,8192,'char');
            image = fread(file_id,[1024,1024],'uint16',0,'b');
            % image = fread(file_id,[1024,1024],'int16',0,'n');
            image = image./max(image(:));
            fclose('all');
            imwrite(image, [image_file_path name '_2_uint16_b' '.bmp'], 'bmp');    
    end
    end
elseif iscell(image_file) ==0
    [pathstr, name, ext] = fileparts(image_file);
    file_id = fopen(image_file)
    if file_id ~= -1
        header = fread(file_id,8192,'char');
        image = fread(file_id,[1024,1024],'uint16',0,'b');
        % image = fread(file_id,[1024,1024],'int16',0,'n');
        image = image./max(image(:));
        fclose('all');
        imwrite(image, [image_file_path name '_2_uint16_b' '.bmp'],'bmp');
    end
end

My problem is that fopen gives -1 most of the time and so I cannot even open the file. However I have just recently found by running the program a few times on the same file that sometimes fopen gives -1 and sometimes it gives a valid id and the conversion goes through... Is there something wrong with fopen?? Any ideas??

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Answer 1

Jan 2012-6-28

2
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/42271-fopen-gives-1-how-to-open#answer_52062

在 MATLAB Online 中打开

fopen replies -1 when it does not find the file. You can test this:

file_id = fopen(image_file{n});
if file_id == -1
  if exist(image_file{n}, 'file')
    error('Cannot open existing file: %s', image_file{n});
  else
    error('Missing file: %s', image_file{n});
  end
end

Unfortunately this does not give the correct warning, the you try to open a folder, because exist(S, 'file') checks for folders also. Anyhow, it should help to find the problem.