ofxCvOpticalFlowPyrLK

extend
#1

Can anyone point me to an example of how to use this addon?

I declare my object:

  
ofxCvOpticalFlowPyrLK     flow;

I initialize in setup():

  
flow.init(mVideoSizeWidth, mVideoSizeHeight, mWindowSizeWidth, mWindowSizeHeight);

I try to calculate the optical flow with two ofxCvGrayscaleImages grabbed from a webcam:

  
flow.calc(mOldImage, mNewImage);

This is where it fails. I keep getting the following errors:

  
OpenCV ERROR: Incorrect size of input array ()  
	in function cvFindCornerSubPix

Any ideas?

#2

Can you zip+post up the rest of it? I’m wondering if the images are getting populated correctly? I’ve used it before w/o problems but that was a little while ago.

j

#3

Zipped and posted my entire Xcode project.

It’s here:

http://drop.io/opticalFlow

#4

Hi astellato

I looked through your project and found the problem was when initializing the optical flow

  
  
flow.init(VIDEO_WIDTH, VIDEO_HEIGHT, VIDEO_WIDTH, VIDEO_HEIGHT);

The last 2 parameters define the size of the search window in each pyramid level.
Setting the window to be as big as your images is what is crashing your application.
Setting a bigger search window will result in a more precise analysis but will slow things down.
The default value is 5, so try experimenting with these values until you get something that works for you.

Best

Rui

#5

That was it. Thanks so much for you help!