Hi,
I am using a function to find difference between 2 images. It takes two 8-bit grayscale images, converts them to CV_32FC1, does a subtraction. Here is the function I am using:
cv::Mat calculateDiff(const cv::Mat &image_one, const cv::Mat &image_two)
{
cv::Mat im1, im2, im_dest;
image_one.convertTo(im1,CV_32FC1);
image_two.convertTo(im2,CV_32FC1);
im1 /= 2.f;
im1 += 128.f;
im2 /= 2.f;
cv::subtract(im1, im2, im_dest);
im_dest.convertTo(im_dest, CV_8UC1);
return im_dest;
}
I have measured the run-time of each major step individually
1. convertTo steps
2. divide by 2, add 128
3. subtract() function
4. convertTo()
When I call this function with images of sizes: 9000 x 6000. I get a run-time of about 900 msec, but each individual step takes a lot less time. Here's one example:
1. Step 1 time: 64 msec
2. Step 2 time: 76 msec
3. Step 3 time: 51 msec
4. Step 4 time: 22 msec
When I called the function: I get the function's runtime: 905 msec
The function call looks like this:
cv::Mat diff_image;
diff_image = calculate_diff(input_one, input_two);
I measure the runtime using cv::getTickCount() and cv::getTickFrequency()
Why is the function's runtime so large where individual step do no take that long? How to improve the runtime?
Kindly Help
Thanks!
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