make Mat from buffer byte

2

pocahentez
63 ●1 ●1 ●9

Hi,

I have a Byte buffer and i want to make a Mat.How can i achieve it using a java code?Should i make a bitmap with the byte buffer first then transform it to Mat?

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4

answered Mar 25 '13

Andrey Pavlenko
1808 ●3 ●18 ●39

You need to allocate a Mat of the appropriate size and type and then use Mat.put() method:

byte buf[] = new byte[100];
//...
Mat m = new Mat(1, 100, CvType.CV_8UC1);
m.put(0, 0, buf);

Comments

1

@AndreyPavlenko Is there a way to create a Mat backed by a NIO ByteBuffer allocated by us. Alternatively, is there a way to get the Buffer of a Mat ?

TimeManx (Sep 12 '13)edit

@TimeManx No, it's not possible: Mat reallocates its buffer on native level when needed, so it's hard to share it between native and java without copying...

Andrey Pavlenko (Sep 14 '13)edit

In JavaCV's OpenCV wrapper, the IplImage has a "getDirectByteBuffer" native method that will from JNI create a new ByteBuffer with the address of the data of the Mat. In my tests modifying pixels like that performs much better than copying byte arrays to and from the Mat.