The <feDisplacementMap> SVG filter primitive uses the pixel values from the image from in2 to spatially displace the image from in.
The formula for the transformation looks like this:
P'(x,y) ← P(x + scale * (XC(x,y) - 0.5), y + scale * (YC(x,y) - 0.5))
where P(x,y) is the input image, in, and P'(x,y) is the destination. XC(x,y) and YC(x,y) are the component values of the channel designated by xChannelSelector and yChannelSelector.