將水印圖像添​​加到大圖像opencv4android

Question

我一直在嘗試將圖像添加到所需位置的大圖像。我發現了一種通過添加加權（src，alpha，water， - ，dst， - ）在opencv中添加水印的方法，但問題是水印和表面圖像應該具有我不想要的相同大小。

找到另一種方式（我猜）

Mat srcMat = cvCanvasImage.submat(top/2, (top + height)/2, left/2, (left + width)/2); 
Imgproc.cvtColor(mat, srcMat, Imgproc.COLOR_GRAY2BGR,4); 

但我不知道如何做到這一點？

謝謝..

UPDATE

 Mat cvCanvasImage = Highgui.imread(Environment.getExternalStorageDirectory() + "/wallpapers/castle.jpg"); 

// Small watermark image 
Mat cvWaterImage = Highgui.imread(Environment.getExternalStorageDirectory() +"/square.png"); 

Size canvasSize = cvWaterImage.size(); 

    int rows = (int) canvasSize.height; 
    int cols = (int) canvasSize.width;  
    int left = 0; 
    int top = 0;   
    int width = rows; 
    int height = cols; 

    Rect ROI = new Rect(left, top, width, height); 
    Core.addWeighted(cvCanvasImage.submat(ROI), alpha, cvWaterImage, beta, 0, cvCanvasImage.submat(ROI)); 

    //now it throws me this error 

          "error: (-209) The operation is neither 'array op array' (where arrays have the same size and the same number of channels), nor 'array op scalar', nor 'scalar op array' in function void cv::arithm_op(const cv::_InputArray&, const cv::_InputArray&, const cv::_OutputArray&, const cv::_InputArray&, int, void (**)(const uchar*, size_t, const uchar*, size_t, uchar*, size_t, cv::Size, void*), bool, void*)" 

Answer 1

我找到了一種方法做是正確的。

Mat b = Highgui.imread(Environment.getExternalStorageDirectory() + "/castle.jpg"); 

// Small watermark image 
Mat a = Highgui.imread(Environment.getExternalStorageDirectory() +"/square.png"); 

Mat bSubmat = b.submat(a.rows(), a.rows()*2, a.cols(), a.cols()*2);   
a.copyTo(bSubmat); 

Highgui.imwrite("mnt/sdcard/SubmatCopyToTest.png", b); 

Answer 2

像這樣的東西應該工作：

Mat waterMark = new Mat(width, height); //assumed as a smaller image than your source mat, with size (width, height). 

Rect ROI = new Rect(x, y, width, height); // Position and size of your watermark; 

Core.addWeighted(source.submat(ROI), alpha, waterMark, beta, gamma, source.submat(ROI));