I wat to open two transparent images inside opencv in C++

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C++

OpenCV

I have 2 transparent images which I want them to be opened in one window in opencv. The code below opens two images but with out alpha channel because it's using (CV_8UC3) and those images which are transparent we should use (CV_8UC4) to show the transparency but when I change the code to (CV_8UC4) the program gives me an error.

I'll put a # on the line of (CV_8UC4);

I'll put a * on the line of error;

//the code turned to 3 parts because of * and #.

microsoft visual studio error dialog shows this error : Unhandled exception at 0x00007FFA48633FB8 in openCV.exe: Microsoft C++ exception: cv::Exception at memory location 0x0000007563FDEA00.
and the console application window shows this one : OpenCV Error: Assertion failed (channels() == CV_MAT_CN(dtype)) in cv::Mat::copyTo, file C:\build\master_winpack-build-win64-vc14\opencv\modules\core\src\copy.cpp, line 272

Is this code suitable for what I want to do?

This code opens multiple images but i've use it for two.

code is:

What I have tried:

void ShowManyImages(string title, int nArgs, ...) {
		int size;
		int i;
		int m, n;
		int x, y;

		// w - Maximum number of images in a row
		// h - Maximum number of images in a column
		int w, h;

		// scale - How much we have to resize the image
		float scale;
		int max;

		// If the number of arguments is lesser than 0 or greater than 12
		// return without displaying
		if (nArgs <= 0) {
			printf("Number of arguments too small....\n");
			return;
		}
		else if (nArgs > 14) {
			printf("Number of arguments too large, can only handle maximally 12 images at a time ...\n");
			return;
		}
		// Determine the size of the image,
		// and the number of rows/cols
		// from number of arguments
		else if (nArgs == 1) {
			w = h = 1;
			size = 300;
		}
		else if (nArgs == 2) {
			w = 2; h = 1;
			size = 1000;
		}
		else if (nArgs == 3 || nArgs == 4) {
			w = 2; h = 2;
			size = 300;
		}
		else if (nArgs == 5 || nArgs == 6) {
			w = 3; h = 2;
			size = 200;
		}
		else if (nArgs == 7 || nArgs == 8) {
			w = 4; h = 2;
			size = 200;
		}
		else {
			w = 4; h = 3;
			size = 150;
		}

		// Create a new 3 channel image
#		Mat DispImage = Mat::zeros(Size(100 + size*w, 60 + size*h), CV_8UC4);

		// Used to get the arguments passed
		va_list args;
		va_start(args, nArgs);

		// Loop for nArgs number of arguments
		for (i = 0, m = 20, n = 20; i < nArgs; i++, m += (0)) {
			// Get the Pointer to the IplImage
			Mat img = va_arg(args, Mat);

			// Check whether it is NULL or not
			// If it is NULL, release the image, and return
			if (img.empty()) {
				printf("Invalid arguments");
				return;
			}

			// Find the width and height of the image
			x = img.cols;
			y = img.rows;

			// Find whether height or width is greater in order to resize the image
			max = (x > y) ? x : y;

			// Find the scaling factor to resize the image
			scale = (float)((float)max / size);

			// Used to Align the images
			if (i % w == 0 && m != 20) {
				m = 20;
				n += 20 + size;
			}

			// Set the image ROI to display the current image
			// Resize the input image and copy the it to the Single Big Image
			Rect ROI(m, n, (int)(x / scale), (int)(y / scale));
			Mat temp; resize(img, temp, Size(ROI.width, ROI.height));
*			temp.copyTo(DispImage(ROI));
		}

		// Create a new window, and show the Single Big Image
		namedWindow(title, 1);
		imshow(title, DispImage);
		waitKey();

		// End the number of arguments
		va_end(args);
	}

	int main(int argc, char** argv)
	{
		Mat img1 = imread("c:\\1.png");
		Mat img2 = imread("c:\\2.png");
		ShowManyImages("Image", 2, img1, img2);

		return 0;
	}