# OpenCV gpu::dft distorted image after inverse transform

I'm working on GPU implementation of frequency filtering of an image. My code works great on CPU (I used something like this) but I have spent whole day trying to make the same work on GPU - without success. I want to apply a filter in the frequency domain hence I need the full (complex) result of the forward transform. I have read that I need to pass two complex matrices (src and dst) to forward dft to obtain full spectrum (32FC2). However, I fail to obtain the same image after inverse transform (the returned image is very distorted).

My code (with the closest result):

```
gpu.img1 = gpu::GpuMat(imgHeight, imgWidth, CV_32FC2);
gpu.img2 = gpu::GpuMat(imgHeight, imgWidth, CV_32FC2);
gpu.img4 = gpu::GpuMat(imgHeight, imgWidth, CV_32FC1);
gpu.img5 = gpu::GpuMat(imgHeight, imgWidth, CV_8UC1);
Mat planes[] = {imageIn, Mat::zeros(imageIn.size(), CV_32FC1)};
merge(planes, 2, imageIn);
gpu::Stream stream;
gpu.img1.upload(imageIn);
gpu::dft(gpu.img1, gpu.img2, gpu.img1.size(), 0, stream);
gpu::dft(gpu.img2, gpu.img4, gpu.img1.size(), DFT_INVERSE | DFT_REAL_OUTPUT | DFT_SCALE, stream);
stream.enqueueConvert(gpu.img4, gpu.img5, CV_8U);
stream.waitForCompletion();
gpu.img5.download(imageOut);
namedWindow("processed",1); imshow("processed", imageOut); waitKey(1000);
```

Your help and suggestions are much appreciated.

Hmm, in contrast to the code from the link you haven't set DFT_COMPLEX_OUTPUT | DFT_SCALE in your forward-dft. Could that be the problem?