Need to copy one image to another image ROI - c++

Question

I am trying to copy one image layer to another image ROI. My code is given below.
Mat4b src= imread("path");
Mat3b dest = imread("path");
Rect roi = Rect(179,539,src.cols,src.rows); //src.cols = 1186 and src.rows= 1134 after scaling.
Mat destinationROI = dest(roi);
src.copyTo(destinationROI);
imwrite("destinationROI.png", destinationROI);
The input src is
The input dest is
But the output got is the same dest image.
Then I tried to save destinationROI befre copying. The output I got is Which is correct one. Copying the src is also working. But it does not make any effect in the dest image.

Answer 1

This is to confirm that #ypnos educated guess was right (nice call, btw).
Take a look at this code, that performs the same operations as yours:
#include <opencv2\opencv.hpp>
#include <iostream>
using namespace cv;
using namespace std;
int main()
{
Mat4b m4b(50, 50, Vec4b(0, 255, 0, 255)); // blue image, 4 channels
Mat3b m3b(100, 100, Vec3b(255, 0, 0)); // green image, 3 channels
cout << "After init:" << endl;
cout << "m4b channels: " << m4b.channels() << endl;
cout << "m3b channels: " << m3b.channels() << endl << endl;
Rect roi(0, 0, 50, 50); // roi
// Create a new header for the data inside the roi in m3b
// No data copied, just a new header.
// So destRoi has same number of channels of m3b
Mat destRoi = m3b(roi);
cout << "After roi:" << endl;
cout << "m4b channels : " << m4b.channels() << endl;
cout << "m3b channels : " << m3b.channels() << endl;
cout << "destRoi channels: " << destRoi.channels() << endl << endl;
// destination type != source type
// destRoi is newly created with the destination type
// destRoi doesn't point anymore to the data in m3b and has 4 channels now
m4b.copyTo(destRoi);
cout << "After copyTo:" << endl;
cout << "m4b channels : " << m4b.channels() << endl;
cout << "m3b channels : " << m3b.channels() << endl;
cout << "destRoi channels: " << destRoi.channels() << endl << endl;
return 0;
}
Output:
After init:
m4b channels: 4
m3b channels: 3
After roi:
m4b channels : 4
m3b channels : 3
destRoi channels: 3
After copyTo:
m4b channels : 4
m3b channels : 3
destRoi channels: 4
Solution
Use both matrices with same number of channels, either by:
Load both images as 3 channels matrices CV_8UC3. In fact the images you posted are both 3 channels
use cvtColor to convert to the same number of channels, before performing roi and copy operations.

Answer 2

Your matrix types do not match. One has four channels, the other one three.
Obviously, copying the content of a 4-channel matrix into a 3-channel matrix can not work.
Unfortunately in some circumstances OpenCV silently falls back to creating a new matrix when it cannot work on the old memory. Most probably, this is such a case. As soon as you perform the copy, destinationROI starts pointing to new memory.
Note that you might be able to prevent this behavior by declaring destinationROI as Mat3b. To make your code work however, both source and destination need to carry the same number of channels.
Both assumptions I make here are only educated guesses though, I did not test the code in question.

Answer 3

your code is too initial. also your images not suit to a perfect result.guess you performed true code on the images you will get an image of who weared to shirt.
Mat4b src= imread("path");// to load 4 channel image : imread("path",IMREAD_UNCHANGED);
Mat3b dest = imread("path");
Rect roi = Rect(179,539,src.cols,src.rows); //src.cols = 1186 and src.rows= 1134 after scaling.
Mat destinationROI = dest(roi);
src.copyTo(destinationROI);
imwrite("destinationROI.png", destinationROI);
i can write a code to get following image ( it is photoshopped just to show result) but it is meaningless with your images.
EDIT 1 :
i edited your code a bit here. take a look //edit 1,2,3 inside the code.
#include <opencv2/imgproc/imgproc.hpp>
#include <opencv2/opencv.hpp>
#include <opencv2/highgui/highgui.hpp>
#include <stdio.h>
using namespace cv;
using namespace std;
float sx, sy;
int tx, ty;
struct TaggingPoint{
int rshx, rshy;
int lshx, lshy;
int topx, topy;
int botx, boty;
}body_points, garment_points;
int main(int argc, char** argv)
{
Mat shirt;
Mat body;
shirt = imread(argv[1], IMREAD_COLOR);
if (shirt.empty())
return -1;
body = imread(argv[2], IMREAD_COLOR);
if (body.empty())
return -1;
body_points.rshx = 418;
body_points.rshy = 706;
body_points.lshx = 1234;
body_points.lshy = 706;
body_points.topx = 838;
body_points.topy = 510;
body_points.botx = 838;
body_points.boty = 1534;
garment_points.rshx = 239;
garment_points.rshy = 147;
garment_points.lshx = 755;
garment_points.lshy = 147;
garment_points.topx = 505;
garment_points.topy = 50;
garment_points.botx = 505;
garment_points.boty = 953;
// edit 1 : when you calculate by this values your shirt image's width will be greater that body image's width
// so to reduce it
sx = (float)(body_points.lshx - body_points.rshx) / (garment_points.lshx - garment_points.rshx)*0.995;
sy = (float)(body_points.boty - body_points.topy) / (garment_points.boty - garment_points.topy);
//scale the image
resize(shirt, shirt, Size(), sx, sy, INTER_LINEAR);
imwrite("shirt.png", shirt);
//translation happened
// tx = body_points.rshx - (sx * garment_points.rshx);
tx = body_points.rshx - (garment_points.rshx);
ty = body_points.rshy - (sy * garment_points.rshy);
//draw one image over another image
//src.copyTo(dst.rowRange(1, 6).colRange(3, 10));
// shirt.copyTo(body.rowRange(tx, shirt.rows).colRange(ty, shirt.cols));
// shirt.copyTo(body.rowRange(100, 1000).colRange(100, 500));
// cvtColor(shirt, shirt, CV_BGRA2BGR);
// cvtColor(body, body, CV_BGRA2BGR);
namedWindow("body");
//Rect roi(cv::Point(tx, ty), Size(shirt.size()));
// Edit 2 : Rect.x = 0
Rect roi = Rect(0,ty,shirt.cols,shirt.rows);
Mat destinationROI = body(roi);
// cvtColor(destinationROI, destinationROI, CV_BGRA2BGR);
// Edit 3 : Create a mask ( it is show purpose only, need improvement )
Mat mask;
cvtColor( shirt, mask, COLOR_BGR2GRAY );
mask = mask < 250;
shirt.copyTo(destinationROI,mask);
imwrite("destinationROI.png", destinationROI);
imshow("body", body);
imwrite("body.png", body);
waitKey();
return 0;
}