Image read in MATLAB and C

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Pravitha A 2020-2-20

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评论： Pravitha A 2020-2-25

I have program to read an image in MATLAB

% open image file
  fd = fopen("i00.dng");
  % read order
  order = fread(fd, 1, 'uint16');
  

I converted this to C as follows:

int order[1234];
FILE *fd=fopen("i00.dng","wb");
fread(order,2,1,fd);
printf("%d",order);	

But the value of order in both cases is different. Did I convert it wrong?What is the exact replica of this code in C?

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James Tursa 2020-2-20

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编辑：James Tursa 2020-2-20

在 MATLAB Online 中打开

An int is likely 4 bytes on your machine, not 2 bytes. Also the expression "order" by itself evaluates as a pointer to the first element, not the first element itself. And you should be opening the file for reading, not writing. So,

unsigned short order[1234];
FILE *fd = fopen("i00.dng","rb"); /* you should check that this result is not NULL */
fread(order,2,1,fd);
printf("%u\n",order[0]);

This is almost a replica of the MATLAB code. Your MATLAB code converts the input to double. If you don't want that, then use an asterisk on the class name:

order = fread(fd, 1, '*uint16');

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Walter Roberson 2020-2-25

If you want big endian then you need to pass in the third parameter to fopen as 'b' or 'ieee-be'. Or you can instead pass that information as the fifth parameter to fread(). Or you can swapbytes() the value that you fread.

Pravitha A 2020-2-25