I am trying to create a sepia effect. This is the code I am trying:
Mat image_copy;
cvtColor(image, image_copy, CV_BGRA2BGR);
Mat kern = (Mat_<char>(4,4) << 0.272, 0.534, 0.131, 0,
0.349, 0.686, 0.168, 0,
0.393, 0.769, 0.189, 0,
0, 0, 0, 1);
cv::transform(image_copy, image, kern);
But it doesn't work. I get a black image. No error, no exception, just black image. Any ideas?
I have tried applying different kernels and they do work. For example:
Mat kern = (Mat_<char>(4,4) << 10, 0, 0, 0,
0, 10, 0, 0,
0, 0, 10, 0,
0, 0, 0, 10);
cv::transform(image_copy, image, kern);
image += cv::Scalar(10, 10, 10, 0);
Please help.
It seems you are creating a kernel of char
values but trying to store float
values.
Make sure to declare the kernel with the same data type as the values you want to store:
#include <cv.h>
#include <highgui.h>
#include <iostream>
int main()
{
cv::Mat image = cv::imread("test.jpg");
if (!image.data)
{
std::cout << "!!! Failed imread" << std::endl;
return -1;
}
cv::Mat image_copy = image.clone();
cv::Mat kern = (cv::Mat_<float>(4,4) << 0.272, 0.534, 0.131, 0,
0.349, 0.686, 0.168, 0,
0.393, 0.769, 0.189, 0,
0, 0, 0, 1);
cv::transform(image_copy, image, kern);
cv::imshow("sepia", image);
cv::waitKey(0);
return 0;
}
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