for(int i=sfPrev.outputs.size()-1;i>=0;--i){
IImage2d i1=sfPrev.outputs.get(i),i2=sfNow.outputs.get(i);
//create preprocessed image
IImage2d preprocessed=new ImageRGBA_SNORM_INT16();
preprocessed.create(i1.getWidth(), i1.getHeight(), true);
preprocess.filter(i1, preprocessed);
Profile.out("pre");
IImage2d flowout=new ImageRGBA_SNORM_INT16();
flowout.create(preprocessed.getWidth(), preprocessed.getHeight(), true);