getting warpPerspective to work

I’m playing around with the image transformation methods in ofxCvImage, specifically warpPerspective and warpIntoMe. I have an ofxCvColorImage called warped and I’m passing elements from an ofPoint array to warpPerspective as follows:

void testApp::setup() {  
// create new array of destination points  
destPoints[0] = ofPoint(20,10);  
destPoints[1] = ofPoint(70,0);  
destPoints[2] = ofPoint(90,120);  
destPoints[3] = ofPoint(20,130);  
void testApp::update() {  
warped.warpPerspective(destPoints[0], destPoints[1], destPoints[2], destPoints[3]);  
void testApp::draw() {  

Doing this, warped displays on the screen at 0,0 but without the transformation applied. I also tried putting the call to warped.warpPerspective in the draw() loop with the same results. Any tips/pointers wouid be greatly appreciated.