Image subtraction weird effect [closed]

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Which error? May be you can post currentFrame, background and foregrounds images

That... might be correct. It looks like that's a transition between two scenes in a video. Look at the grid on the floor. And if each channel is being thresholded separately, that would explain the colors, which appear to be combinations of 0 and 255 values in each of the three channels.

Ok, things to check.

You're doing absdiff into the Mat foregrounds, and the threshold on a Mat called foreground. Is that a typo or a bug?

Secondly, I diff those images and threshold and I get something much more reasonable, without all those vertical lines.

Yes, it was a typo, I updated the code in the question. But it means that wasn't the problem.

Using this code (opencv 3.3-dev vs2015):

Mat foreground,background;
foreground = imread("15075018148975703.png", IMREAD_COLOR);
background = imread("15075018217250966.jpg", IMREAD_COLOR);
cv::absdiff(foreground, background, foreground);
cv::threshold(foreground, foreground, 25, 255, cv::THRESH_BINARY);
imshow("r", foreground);
waitKey();

I got this image :

Things to check: Check whether you load the images correctly. Try loading both as Grayscale images and check once. As pointed by @Tetragramm there looks a transition in the two scenes.