iOS 和 OpenCV 错误：断言在 PhaseCorrelateRes 中失败

我正在尝试在iOS中使用OpenCV检测两个图像之间的偏移。我使用的函数是phaseCorrelate，它应该返回给定2个cv::Mat图像的Point2d。我按照这里的示例代码将UIImage转换为Mat，然后将Mat转换为CV_32F类型。但我一直收到这个错误：

OpenCV Error: Assertion failed (src1.type() == CV_32FC1 || src1.type() == CV_64FC1) in            phaseCorrelateRes, file /Users/alexandershishkov/dev/opencvIOS/opencv-2.4.7/modules/imgproc/src/phasecorr.cpp, line 498
libc++abi.dylib: terminating with uncaught exception of type cv::Exception: /Users/alexandershishkov/dev/opencvIOS/opencv-2.4.7/modules/imgproc/src/phasecorr.cpp:498: error: (-215) src1.type() == CV_32FC1 || src1.type() == CV_64FC1 in function phaseCorrelateRes

我不明白为什么会出现这个错误，因为我已经将Mat类型转换为CV_32F。仅供参考：我之所以没有转换为CV_64F，是因为它占用了大量内存，而且iOS中的应用程序会因内存过大而立即关闭。

以下是发生错误的代码片段（在phaseCorrelate调用时）：

#ifdef __cplusplus
-(void)alignImages:(NSMutableArray *)camImages
{
int i;
Mat matImages, refMatImage, hann;
Point2d pcPoint;
for (i = 0; i < [camImages count]; i++) {
    if(i == 0){
        UIImageToMat([camImages objectAtIndex:i], refMatImage);
        refMatImage.convertTo(refMatImage, CV_32F);
        createHanningWindow(hann, refMatImage.size(), CV_32F);
    }
    else{
        UIImageToMat([camImages objectAtIndex:i], matImages);
        matImages.convertTo(matImages, CV_32F);
        pcPoint = phaseCorrelate(refMatImage, matImages, hann);
        NSLog(@"phase correlation points: (%f,%f)",pcPoint.x, pcPoint.y);
    }
}
NSLog(@"Done Converting!");
}
#endif