在MATLAB中读取.img文件并

Question

I am quite new to MATLAB. I want to read a .img file in MATLAB and want to export it is any generic image format. I don't have any information about the file (ie image resolution) I tried reading the file using fread command.

fid=fopen('image.img');
A=fread(fid,256*378,'unit8=>unit8');
fclose(fid);
b=reshape(A,256,378);
imshow(A);

I'm able to open it only if I know the resolution of my .img file. Please help me do the same without knowing the resolution to start with or if anyone can suggest a better way to do it.

Download the .img file here .

Answer 1

It is not clear what kind of .img file you are dealing with. .img files are normally disk image files. There are different file formats for Mac, Windows and ISO. However, it sounds like you are asking about a graphic image file format, which might be proprietary. If you know what program was used to create the .img file, you may be able to learn more about its internal format.

The dir function can be used to determine the total number of bytes in the file, which will allow you to read the file using fread. However, you would still need to know the dimensions to reshape the image.

Answer 2

If you want to process images, Matlab has a nice Image Processing Toolbox and I strongly suggest you to read the help/manual. You'll find several built-in functions ready-to-use that can sort you out.

imageinfo() is one of that: will show a structure with several infos regarding the image, imread() will import your image in a matrix form, mat2grey() will convert your RGB image in a greyscale image...and the list goes on.

Do not use fopen() / fread() / fclose() with images: such functions are mainly used to deal with text files.

PS: the link you provided contains a disk image (of course, given that extension, as @Herb correctly pointed out).

Answer 3

The sintax of fread() function in your code is wrong.

First, the datatype is uint8 not unit8 .

• U is unsigned, which means: All values are positive (no negative "sign" allowed)

• INT is integers, which means: All values are whole numbers, 0,1,2,3...

• 8 is Only 8 bits of information, which means: the max value is 255 and the min value is 0.

Second, the 256*378 argument in the function fread() will create an another dimension of this image. Thus the correct way of this is using [] .

f = fopen('image.img')
image = fread(f, [256 378], '*uint8');
imshow(image,[])

imwrite(image, 'davinci.jpg', 'jpg')
whos image
Variables in the current scope:

   Attr Name          Size                     Bytes  Class
   ==== ====          ====                     =====  =====
        image         256x378                  96768  uint8

Total is 96768 elements using 96768 bytes

This question may be a little bit equally with this question

• references 1