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[英]How to use opencv to acess images to use for alpha blending in java for android
[英]OpenCV java alpha Blending
我正在尝试移植以下代码(从 C++ 到 Java)以在我的图像之间进行良好的 alpha 混合,但它不起作用:
#include opencv2/opencv.hpp
using namespace cv;
using namespace std;
int main(int argc, char** argv)
{
// Read the images
Mat foreground = imread("puppets.png");
Mat background = imread("ocean.png");
Mat alpha = imread("puppets_alpha.png");
// Convert Mat to float data type
foreground.convertTo(foreground, CV_32FC3);
background.convertTo(background, CV_32FC3);
// Normalize the alpha mask to keep intensity between 0 and 1
alpha.convertTo(alpha, CV_32FC3, 1.0/255); //
// Storage for output image
Mat ouImage = Mat::zeros(foreground.size(), foreground.type());
// Multiply the foreground with the alpha matte
multiply(alpha, foreground, foreground);
// Multiply the background with ( 1 - alpha )
multiply(Scalar::all(1.0)-alpha, background, background);
// Add the masked foreground and background.
add(foreground, background, ouImage);
// Display image
imshow("alpha blended image", ouImage/255);
waitKey(0);
return 0;
}
代码可以在这里找到: https : //www.learnopencv.com/alpha-blending-using-opencv-cpp-python/还有我的 Java 版本:
public static Mat alphaBlend(Mat background, Mat foreground) {
Vector<Mat> rgba = new Vector<Mat>();
// split RBGA image for separate channels
Core.split(background, rgba);
// get alpha channel
Mat alpha = rgba.get(3);
// Convert Mat to float data type
foreground.convertTo(foreground, CvType.CV_32FC3);
background.convertTo(background, CvType.CV_32FC3);
// Normalize the alpha mask to keep intensity between 0 and 1
alpha.convertTo(alpha, CvType.CV_32FC3, 1.0/255); //
Imgproc.cvtColor(alpha,alpha, Imgproc.COLOR_GRAY2BGRA,4);
Mat outImage = Mat.zeros(foreground.size(),foreground.type());
// Multiply the foreground with the alpha matte
Core.multiply(alpha, foreground, foreground);
Mat kernel = new MatOfDouble(1.0);
Core.subtract(kernel, alpha, alpha);
// Multiply the background with ( 1 - alpha )
Core.multiply(alpha, background, background);
// Add the masked foreground and background.
Core.add(foreground, background, outImage);
Core.divide(new MatOfDouble(255), outImage,outImage);
return outImage;
}
我认为我的问题是将其移植到 Java 中:
multiply(Scalar::all(1.0)-alpha, background, background);
任何帮助,将不胜感激!
谢谢
编辑:这里是一个工作版本,但边框不混合透明像素,导致图像交点的边框处出现空白像素/线:
private static Mat merge(Mat background, Mat foreground) {
Vector<Mat> rgba = new Vector<Mat>();
// split RBGA image for separate channels
Core.split(background, rgba);
// get alpha channel
Mat alpha = rgba.get(3);
// Convert Mat to float data type
// Normalize the alpha mask to keep intensity between 0 and 1
alpha.convertTo(alpha, CvType.CV_32FC3, 1.0/255); //
Mat dst = new Mat(256,256,CvType.CV_8UC4);
alpha.convertTo(alpha,CvType.CV_8UC1);
Mat alphaInv = new Mat();
// invert the mask
Core.absdiff(new MatOfDouble(1.0), alpha, alphaInv);
foreground.copyTo(dst, alphaInv);
// case where foreground is full JPEG in BGR
if(dst.type() != CvType.CV_8UC4) {
Imgproc.cvtColor(dst, dst, Imgproc.COLOR_BGR2BGRA, 4);
}
background.copyTo(dst, alpha);
return dst;
}
我建议使用 Core 的addWeighted方法进行基本的 alpha 混合。
看起来您想要一个基于掩码的可变 alpha 混合,您需要按照 api 指定的顺序排列参数,以便进行加法/ 减法/ 乘法等基本操作。 对于您的乘法,这意味着标量应该是第二个参数。 对于您的减法,这意味着标量应该再次成为第二个参数(我发现自己将矩阵乘以负 1,然后添加到标量值)。
根据您共享的链接,目标似乎只是使用图像遮罩,我认为有一种更简单的方法,即使用copyTo函数。 尝试将它放在您的主要功能中,并在它运行时移动到您的功能:
// Read the images
Mat foreground = Imgcodecs.imread("puppets.png");
Mat background = Imgcodecs.imread("ocean.png");
Mat mask = Imgcodecs.imread("puppets_alpha.png");
Mat notMask = new Mat();
Core.bitwise_not(mask, notMask);
Mat result = new Mat();
Core.copyTo(background, result, mask);
Core.copyTo(foreground, result, notMask);
Imgcodecs.imwrite("result.png", result);
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