MATLAB: Reading both Bytes of a Unsigned 16-bit binary file

Question

I have a binary Band Sequential (1-band, BSQ file), which is an unsigned 16-bit (2-byte) integer.

Currently I'm reading the whole (image) through multibandread:

img=multibandread('IMAGE.bsq',[400 400 1],'uint16',0,'bsq','n');

What process in MATLAB would allow me to read both bytes individually? i.e. I would like to read the file into 2 new arrays in MATLAB e.g. byte1 (400x400x1) and byte2 (400x400x1).

Can this be achieved through fread? I note in the 'precision' section it is possible to skip source values (e.g. 'N*source=>output'), but I'm unsure of the exact process.

Did you try specifying `'uint8'` instead of `'uint16'`, obtaining the result and then dividing it into two images? Or alternatively splitting your current result into two images using bitwise operations? — Eitan T, Jan 17 '13 at 16:32
I need to extract both bytes from the `uint16` array - would reading as `uint8` achieve this? (I'm more interested in the data contained in the second byte though) — MBL, Jan 17 '13 at 16:34

Eitan T · Accepted Answer · 2013-01-17T17:20:59.760

4

One way would be splitting your current img with bitwise operations. The LSB image would be:

img1 = bitand(img, 255);   %// 0x00FF

and the MSB image would be:

img2 = bitsra(img, 8);

Not mandatory, but maybe you'll also want to convert these into uint8s:

img1 = uint8(img1);
img2 = uint8(img2);

edited Jan 17 '13 at 17:20

answered Jan 17 '13 at 16:37

Eitan T

32,660
14
72
109

2

`img2 = bitsra(img, 8);` would be better. – Ben Voigt Jan 17 '13 at 16:48
2

That seems to have done it. I'm only really interested in the MSB which looks like it comes with reasonable values using `img1 = bitand(A, 255); %// 0x00FF`. Cheers – MBL Jan 17 '13 at 16:51
@MBL I think the `img1` is LSB, not MSB. The `img2` is MSB. – Léo Léopold Hertz 준영 Mar 20 '16 at 08:06
@Masi That is what I stated in the answer, no? – Eitan T Mar 20 '16 at 09:24
1

@EitanT Yes, your answer is correct. MBL comments different in the second comment: *MSB --- img1*. – Léo Léopold Hertz 준영 Mar 20 '16 at 10:54
@EitanT: For people without the Fixed-Point Designer toolbox you might want to include your first answer with `bitand` as well. – Gelliant Mar 27 '18 at 11:28

MATLAB: Reading both Bytes of a Unsigned 16-bit binary file

1 Answers1