How to convert 2 byte data to integer?

452 ビュー (過去 30 日間)
Tharindu Weerakoon 2015 年 1 月 26 日
コメント済み: mohd akmal masud 2018 年 2 月 20 日
I have a two byte data (unsigned) as array.
e.g. x=[255 67]
I read the data from a sensor giving a stream of byte data (unsigned 0 to 255). From them I select corresponding two-byte of data set for necessary parameter calculation.
I want to convert this into an Integer value or a double value to do real mathematic calculations.
I tried with.
x=uint8([1 0]) y=typecast(x,'uint32') % but this gives an error.
if I use: x=uint16([255 67]) y=typecast(x,'uint32')
4391167
I don't how to check the answer is correct or not. Or the conversion syntax is correct?
Can anyone give me the code for correct 2-byte data conversion to integer..!

サインインしてコメントする。

採用された回答

Guillaume 2015 年 1 月 26 日

You were nearly there. combining two bytes (uint8) does not make a 32-bit number (uint32), but a 16-bit numbers (uint16), so:
x = [255 67];
y = typecast(uint8(x), 'uint16');
You haven't specified the endianness of your data, nor that of your machine. If the two don't match, you'll have to swapbytes afterward:
truey = swapbytes(y); %if one is big-endian and the other litte-endian
1 件のコメント表示非表示 なし
Tharindu Weerakoon 2015 年 1 月 27 日
Hi Guillaume,
Actually I have the byte array in my C# program like: (simply, not the real commands) byte[] x; x={20, 0, 1, 255, 178, 0, 35, 255, 138}
Y1: convert the byte value 20 (lower byte from right side) to integer (int in C#) and answer should equal to 20.
Y2: two byte array [0 1] (1: lower byte) should be converted to int16 and then the answer should be equal to 1
Y3: for the two byte array [255 178] (lower byte is 178)should be converted to the int16 and then the answer divided by 32767.0f/360.0f in C# should give the answer looks like -0.93387.
Y4: for the two byte array [0 35] (lower byte is 35) should be converted to the int16 and then dividing by 32767.0f/360.0f should give the answer looks like 0.56032
Y5: for the two byte array [255 138] (lower byte is 138) should be converted to int16 and then it is divided by 32767.0f/3.0f should give the answer looks like -0.01053.
For your reference I have put my C# code here to get more clear understanding about my problem.
/// <summary>
/// Constructor
/// </summary>
/// <param name="X"></param>
public DataConversion(byte[] X)
{
//Decoding
int index = 0;
Y1= (int)X[index++];
Y2 = (Decode2byte(X[index++], X[index++]) == 1);
double bias = 0;
bias = 32767.0f / 360.0f;
Y3 = Decode2byte(X[index++], X[index++]) / bias;
Y4 = Decode2byte(X[index++], X[index++]) / bias;
bias = 32767.0f / 3.0f;
Y5= Decode2byte(X[index++], X[index++]) / bias;
}
/// <summary>
/// Two byte data conversion to int16
/// </summary>
/// <param name="data1"></param>
/// <param name="data2"></param>
/// <returns></returns>
private Int16 Decode2byte(byte data1, byte data2)
{
return (Int16)(data1 << 8 | data2);
}
Could you please tell me how can I do this in matlab

サインインしてコメントする。

その他の回答 (2 件)

Image Analyst 2015 年 1 月 26 日

I don't know which element of x is the upper or lower byte, so I did it both ways. Try this:
x=[255 67]
% Display bytes in binary.
dec2bin(x(1))
dec2bin(x(2))
% If x(1) is the most significant byte:
x_uint16 = uint16(256*x(1) + x(2))
dec2bin(x_uint16)
% If x(1) is the least significant byte:
x_uint16 = uint16(256*x(2) + x(1))
dec2bin(x_uint16)
Note that x must be a double or a uint16 variable, not a char or uint8 variable or else you can't multiply by 256.
In the command window, you'll see:
x =
255 67
ans =
11111111
ans =
1000011
x_uint16 =
65347
ans =
1111111101000011
x_uint16 =
17407
ans =
100001111111111
You can replace uint16 by double if you want the data type to be double instead of uint16.
1 件のコメント表示非表示 なし
Tharindu Weerakoon 2015 年 1 月 27 日
Hi,
Actually I get the data as unsigned byte data (uint8) (0 to 255 ) and I want then to convert into signed int16 (-2^15 to 2^15-1)data.
I have the byte array in my C# program like: (simply, not the real commands) byte[] x; x={20, 0, 1, 255, 178, 0, 35, 255, 138}
Y1: convert the byte value 20 (lower byte from right side) to integer (int in C#) and answer should equal to 20.
Y2: two byte array [0 1] (1: lower byte) should be converted to int16 and then the answer should be equal to 1
Y3: for the two byte array [255 178] (lower byte is 178)should be converted to the int16 and then the answer divided by 32767.0f/360.0f in C# should give the answer looks like -0.93387.
Y4: for the two byte array [0 35] (lower byte is 35) should be converted to the int16 and then dividing by 32767.0f/360.0f should give the answer looks like 0.56032
Y5: for the two byte array [255 138] (lower byte is 138) should be converted to int16 and then it is divided by 32767.0f/3.0f should give the answer looks like -0.01053.
For your reference I have put my C# code here to get more clear understanding about my problem.
/// <summary>
/// Constructor
/// </summary>
/// <param name="X"></param>
public DataConversion(byte[] X)
{
//Decoding
int index = 0;
Y1= (int)X[index++];
Y2 = (Decode2byte(X[index++], X[index++]) == 1);
double bias = 0;
bias = 32767.0f / 360.0f;
Y3 = Decode2byte(X[index++], X[index++]) / bias;
Y4 = Decode2byte(X[index++], X[index++]) / bias;
bias = 32767.0f / 3.0f;
Y5= Decode2byte(X[index++], X[index++]) / bias;
}
/// <summary>
/// Two byte data conversion to int16
/// </summary>
/// <param name="data1"></param>
/// <param name="data2"></param>
/// <returns></returns>
private Int16 Decode2byte(byte data1, byte data2)
{
return (Int16)(data1 << 8 | data2);
}
Could you please tell me how can I do this in matlab

サインインしてコメントする。

Tharindu Weerakoon 2015 年 1 月 27 日

Hello everyone,
Thanks a lot for the help. Finally I could do it.
% Two byte array [lower bit , higher bit] x=uint8[178 255]
% convert to signed int16 y=typecast(x,'int16')
% if want to use this for other mathematical calculations, it should be converted to the double. z=double(y)
% simple math operation. int16 range value is -32768 ~32767 Out=(z/32767)*250
Result will be x = 178 255
y = -78
z = -78
out = -0.595110934781945
Thanks again all
1 件のコメント表示非表示 なし
mohd akmal masud 2018 年 2 月 20 日
hi all,
i have image dicom 16 bit. Like below my image:
>> whos P
Name Size Bytes Class Attributes
P 256x256 131072 int16
My problem is, 16 bit image can stored pixel value till 32767 only. Now i want change it to 32 bit or 64 bit so that the pixel value can stored more than that, and corresponding how much activity radionuclides i used to diagnosed patient.
can you help to convert that using matlab? or anyway to solve it?

サインインしてコメントする。

Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!

Translated by