Image sharpening by grid warping

We develop a post-processing algorithm which enhances the results of the existing image deblurring methods. It performs additional edge sharpening using grid warping. The idea of the proposed algorithm is to transform the neighborhood of the edge so that the neighboring pixels move closer to the edge, and then resample the image from the warped grid to the original uniform grid. The proposed technique preserves image textures while making the edges sharper. The effectiveness of the method is shown for basic deblurring methods on LIVE database images with added blur and noise.

The proposed algorithm is not posed as a global image deblurring method. It enhances only image edges neighborhood and practically does not affect image textures.

The proposed algorithm has the following advantages and features:

  • 1. The best results are achieved when grid warping is used as a post-processing method after global image deblurring methods. Traditional image deblurring methods improve overall image quality while grid warping pays special attention to image edges.
  • 2. No artifacts like ringing effect or noise amplification are introduced because pixel values are not changed.
  • 3. Unlike morphological methods and shock filters, the resulting images look natural and do not inevitably become piecewise constant.
  • 4. It can be used as a standalone method of image sharpening. It is a good choice in the presence of strong noise and complex and non-uniform blur kernel.

You can try this method using our program.

Grid warping idea:

Traditional sharpening approach:
pixel values are modified

Grid warping approach:
pixels are shifted

Results:

Blurred and noisy image

Wiener filter deblurring

Wiener + warping

SSIM improvement after warping

Average PSNR values for images from LIVE database with added blur and noise.
Grid warping is applied and a post-processing algorithm:

MethodNo warpingWith warping
Blurred and noisy images22.8423.25
Unsharp masking23.0023.36
TV regularization23.3023.40
Low-frequency TV regularization23.0823.18
TVMM23.3123.48
Lucy-Richardson23.8323.99
Wiener24.0024.17
MatLab blind deconvolution23.7923.96

Publications

2016

A. S. Krylov, A. V. Nasonov, A. V. Razgulin, T. E. Romanenko. “A post-processing method for 3D fundus image enhancement” // In: International Conference on Signal Processing (ICSP2016). Chengdu, China, 2016, pp. 49−52. PDF.

A. S. Krylov, A. A. Nasonova, A. V. Nasonov. “Image Enhancement by Non-iterative Grid Warping” // Pattern Recognition and Image Analysis, Vol. 26, No. 1, 2016, pp. 161−164. PDF.

A. D. Gusev, A. V. Nasonov, A. S. Krylov. “Parallel implementation of image sharpening method using grid warping” // In: Proceedings of the 26th International Conference on Computer Graphics and Vision GraphiCon'2016. 2016, pp. 294−297. PDF.

2015

A. Nasonova, A. Krylov. “Deblurred images post-processing by Poisson warping” // IEEE Signal Processing Letters, Vol. 22, No. 4, 2015, pp. 417−420. PDF.

A. S. Krylov, A. V. Nasonov. “3D image sharpening by grid warping” // Lecture Notes in Computer Science (IScIDE2015), Vol. 9242, 2015, pp. 441−450. PDF.

A. S. Krylov, A. A. Nasonova, A. V. Nasonov. “Image warping as an image enhancement post-processing tool” // In: Proceedings of 9th Open German-Russian Workshop on Pattern Recognition and Image Understanding (OGRW 2014). Koblenz, Germany, 2015, pp. 132−135. PDF.

2014

A. Nasonova, A. Nasonov, A. Krylov, I. Pechenko, A. Umnov, N. Makhneva. “Image warping in dermatological image hair removal” // Lecture Notes in Computer Science, Vol. 8815, ICIAR 2014, Vilamoura, Algarve, Portugal, 2014, pp. 159−166. PDF.

A. Krylov, A. Nasonova, A. Nasonov. “Grid warping for image sharpening using one-dimensional approach” // In: Proceedings of International Conference on Signal Processing (ICSP2014). IEEE, Hangzhou, China, 2014, pp. 672−677. PDF.

А. А. Насонова. «Деформационный метод повышения разрешения изображений с сохранением резкости границ» // в: Труды 16-й международной конференции «Цифровая обработка сигналов и её применение» (DSPA'2014), т. 2. Москва, 2014, с. 452−455. PDF.

А. А. Насонова, А. С. Крылов. «Повышение резкости изображений на основе деформации пиксельной сетки» // в: Тезисы конференции «Ломоносовские чтения 2014». ВМК МГУ, 2014, с. 40−41.

A. Nasonov, A. Krylov. “Grid warping in total variation image enhancement methods” // In: Proceedings of International Conference on Image Processing (ICIP2014). IEEE, Paris, France, 2014, pp. 4517−4521. PDF.