问题
I am trying to blend two images as shown here.
This is my whole code
#include <cv.h>
#include <highgui.h>
#include <iostream>
using namespace cv;
int main( int argc, char** argv )
{
double beta; double input;
Mat src1, src2, dst;
/// Ask the user enter alpha
std::cout<<" Simple Linear Blender "<<std::endl;
std::cout<<"-----------------------"<<std::endl;
src1 = imread("face.jpg");
src2 = imread("necklace1.png");
if( !src1.data ) { printf("Error loading src1 \n"); return -1; }
if( !src2.data ) { printf("Error loading src2 \n"); return -1; }
double alpha = 0.1; // something
int min_x = ( (src1.cols - src2.cols)/2 );
int min_y = ( (src1.rows - src2.rows)/2 );
int width, height;
// min_x, min_y should be valid in src1 and [width height] = size(src2)
cv::Rect roi = cv::Rect(min_x, min_y, src2.cols, src2.rows);
// "out_image" is the output ; i.e. src1 with a part of it blended with src2
cv::Mat out_image = src1.clone();
// Set the ROIs for the selected sections of src1 and out_image (the same at the moment)
cv::Mat src1_roi= src1(roi);
cv::Mat out_image_roi = out_image(roi);
// Blend the ROI of src1 with src2 into the ROI of out_image
cv::addWeighted(src1_roi,alpha,src2,1-alpha,0.0,out_image_roi);
imshow( "Linear Blend", out_image );
waitKey(0);
return 0;
}
My input images are
But the output got is
I want this necklace as transparent as before. How to do it?
I tried cvtColor( out_image_roi,out_image_roi, CV_BGR2BGRA );
before cv::addWeighted(src1_roi,alpha,src2,1-alpha,0.0,out_image_roi);
But then the output is only the face image.
回答1:
You can blend only pixels that have alpha channel greater than 0, with a custom loop. I think that the code is more clear than an explanation:
#include <opencv2\opencv.hpp>
#include <iostream>
using namespace cv;
using namespace std;
int main()
{
Mat3b bkg = imread("path_to_girl_image");
Mat4b fgd = imread("path_to_necklace_image", IMREAD_UNCHANGED);
int x = 150;
int y = 500;
double alpha = 0.5; // alpha in [0,1]
Mat3b roi = bkg(Rect(x, y, fgd.cols, fgd.rows));
for (int r = 0; r < roi.rows; ++r)
{
for (int c = 0; c < roi.cols; ++c)
{
const Vec4b& vf = fgd(r,c);
if (vf[3] > 0) // alpha channel > 0
{
// Blending
Vec3b& vb = roi(r,c);
vb[0] = alpha * vf[0] + (1 - alpha) * vb[0];
vb[1] = alpha * vf[1] + (1 - alpha) * vb[1];
vb[2] = alpha * vf[2] + (1 - alpha) * vb[2];
}
}
}
imshow("Girl with necklace", bkg);
waitKey();
return 0;
}
Result:
来源:https://stackoverflow.com/questions/32478976/want-transparent-image-even-after-blending