Image Background Transparency - OpenCV

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Thanks for the reply, Can you tell me how to pass this parameter to target mat?

In C++ this would be done like this when you declare targetMat:

cv::Mat targetMat(rows, cols, CV_8UC4);

targetSize = new Size(newWidthHeight[0], newWidthHeight[1]);

I'm doing this, but not getting transparency. targetSize = new Size(newWidthHeight[0], newWidthHeight[1]); Scalar colorScalar = new Scalar(125,125,200,0.6); targetMat = new Mat(targetSize, scaledImage.type(),colorScalar);

If i omit the colorScalar from Mat function, default black background is applied. I can see different colors in background if i change Scalar values.

You are setting targetMat with the same type as scaledImage which is probably not CV_8UC4. Try:

targetMat = new Mat(targetSize, CV_8UC4, colorScalar);

After making change as you suggested, i lost my watermark image(above rotated image).

For CV_8UC3 it is working. I think i am missing alpha value, but don't know how to solve this.

You are losing the image because you are defining colorScalar as:

Scalar colorScalar = new Scalar(125,125,200,0.6)

The alpha channel on a CV_8UC4 image is represented by a uchar ([0-255]) and you are giving it a value of 0.6 which will truncate to 0 (which means fully transparent, and hence making the whole image fully trasparent)

Try this instead:

Scalar colorScalar = new Scalar(125, 125,200, 154);

This should make your watermark appear about 60% transparent