getRegion and copyTo issues about opencv4nodejs HOT 7 CLOSED

i know what's wrong. my png image has problem.
Thank you again.

from opencv4nodejs.

It is not really clear to me what you are trying to achieve and what you expect the output to be. Could you please give some more details?

from opencv4nodejs.

getRegion will return a Mat pointing to the subregion, meaning if you change the data of the "region" Mat, the changes will reflect on the original Mat "mat".

i just want to know copyTo function can be change orignal Mat?.

in opencv3 C++

cv::Mat image = cv::imread("D:/imagewarping/testresult/hansome.jpg");
cv::Mat logo = cv::imread("D:/imagewarping/testresult/trans.jpg");
cv::Mat mask = cv::imread("D:/imagewarping/testresult/trans.jpg", 0);
cv::Mat imageROI;
imageROI = image(cv::Rect(182, 63, 215, 235));
logo.copyTo(imageROI, mask);
cv::namedWindow("result");
cv::imshow("result", image);

now i want to do something like C++ Code can do.

my english is so poor. sorry

from opencv4nodejs.

I see. CopyTo should work as expected. I think the problem here is that newFrame.cvtColor returns a new Mat (e.g. a new copy) as well.

In order to copy it into the "newFrame" try the following:

let newFrame = frame.getRegion(new cv.Rect(400, 0, 480, 720)).cvtColor(cv.COLOR_BGR2RGBA);
let imageROI = newFrame.getRegion(new cv.Rect(0, 0, addMat.cols, addMat.rows));
let cpTo = addMat.copyTo(imageROI, mask);

from opencv4nodejs.

ok this is work .
thank you very much.
the last quesiotn.
my '/assets/images/1_4.png' has Transparent part。
but when i do addMat.copyTo. Transparent part change to white color.

from opencv4nodejs.

Hmm actually I am not sure how to process images with transparency in OpenCV. How do you know the transparent part is changed to white, isn't the transparency expressed by the alpha channel in RGBA? Maybe imshow can not display RGBA images properly, is it also white when saving the output with imsave?

from opencv4nodejs.

OK. i use canvas to display image.
ctx.putImageData(imgData, 0, 0).
in canvas display white.

from opencv4nodejs.