Javacv: How to convert between Mat and byte[]

[blackredscarf]

This is different from opencv's API. I'm not familiar with it.

[saudet]

new Mat(byte[]) works

[blackredscarf]

@saudet And Mat to byte[] ?

[saudet]

Mat.data().get(byte[]), pretty much the same as the C++ API.

[blackredscarf]

@saudet But new Mat(byte[]) not available

[saudet]

Yes it is:
http://bytedeco.org/javacpp-presets/opencv/apidocs/org/bytedeco/javacpp/opencv_core.Mat.html#Mat-byte...-

[blackredscarf]

@saudet I mean, the image of new Mat(byte[]) is not the same as the original image. It's a long gray picture.

this is my test code:

    public static byte[] Mat2Bytes(Mat mat){
        byte[] b = new byte[mat.channels() * mat.cols() * mat.rows()];
        mat.data().get(b);
        return b;
    }

    public static Mat Bytes2Mat(byte[] b){
        return new Mat(b);
    }
    public static void main(String[] args) throws IOException {
        Mat img = imread(getPath("test4.jpg"));

        byte[] b = Mat2Bytes(img);
        Mat img2 = Bytes2Mat(b);
        opencv_highgui.imshow("FacesOfImage", img2);
        opencv_highgui.waitKey(0);
    }

[saudet]

You never mentioned anything about an image. You'll need to clarify what
you want to do if you expect someone to help you.

[saudet]

An image has width, height, depth, and type so you'll also need to specify that, for example:

Mat img2 = new Mat(rows, cols, CV_8UC(channels), new BytePointer(b));

[blackredscarf]

@saudet thanks very much

[tzolov]

@saudet, can i use a similar approach to initialize a Mat from a long[][] array ?
Or do i need to use the indexer and put it pixel by pixel?

[saudet]

There's currently no helper for arrays of arrays, so yes, we need to do it manually.

[tzolov]

Btw, the Mat.data().get(byte[]) seems to be skewing the image! So for the moment i'm using this workaround:

byte[] data = ((DataBufferByte) Java2DFrameUtils.toBufferedImage(mat).getRaster().getDataBuffer()).getData();

Maybe there are some additional image parameters i need to consider before transforming to bytes?

[saudet]

We need to consider the "step" or "stride", but just use an indexer, it will do that for you.

[tzolov]

Ok, got it