It is the process of taking pixels from one place in the image and locating them in another position in a new image.
To accomplish the mapping process, it might be necessary to do some interpolation for non-integer pixel locations, since there will not always be a one-to-one-pixel correspondence between source and destination images.
We can express the remap for every pixel location (x,y) as:
g(x,y) = f ( h(x,y) )
where g() is the remapped image, f() the source image and h(x,y) is the mapping function that operates on (x,y)
注意这里对函数的理解，也就是remapping的过程，举个简单的例子，当remapping函数为h(x,y)=(x+1, y+1)时， 新的图像g(3,4) = f(h(3, 4)) = f(4, 5), 也就是说新得到的图像(3,4)处的像素点原来是在原图像的(4, 5)处。