System information (version)

• OpenCV => all
• Operating System / Platform => all
• Compiler => all

Detailed description

There are a number of methods in OpenCV that accept or generate pixel coordinates as floating point numbers, remap is one of those methods I am using. I googled for a while trying to find out whether this method places centre of the top-left pixel at 0,0 or at 0.5,0.5, some conflicting information came up:

http://answers.opencv.org/question/87923/sub-pixel-coordinate-origin/
http://answers.opencv.org/question/35111/origin-pixel-in-the-image-coordinate-system-in-opencv/

It seems that the correct answer is 0,0 is the centre of the top left pixel, judging by this commit:

e646f9d

There should be a place somewhere in the documentation where the pixel coordinate system is properly defined, not just for the integer case. One paragraph stating what the coordinates of the centre and the four corners of the top left pixel are would suffice.