Gradient-based image noise level estimation method

A technology of image noise and noise level, which is applied in the field of computer image processing, can solve problems such as influence, and achieve the effects of improving calculation accuracy, robust algorithm, and wide application range

Inactive Publication Date: 2016-11-16
ZHEJIANG UNIVERSITY OF MEDIA AND COMMUNICATIONS
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Problems solved by technology

However, this type of method has its limitations, because the obtained difference image ofte...

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  • Gradient-based image noise level estimation method

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Embodiment Construction

[0030] The present invention will be described in detail below in conjunction with specific embodiments. The main steps of the gradient-based image noise level estimation method of the present invention are:

[0031] (1) Given a noisy image with a noise level to be estimated, it is denoted as I (in this embodiment, the size of I is 256×256 pixels), and I is divided into blocks whose size is N×N (during specific implementation, N= 28) (scan on the image I according to the interval (step length) of 2 pixels, from left to right, and from top to bottom, to obtain multiple image blocks with a size of N×N).

[0032] (2) For each image block P obtained in step (1) i (i=1,2,...,n), where n is the number of image blocks, the following operations are performed:

[0033] (2-1) According to the following formula, calculate the image block P i The horizontal and vertical gradients of each pixel in :

[0034] ∂ P i ...

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Abstract

The invention discloses a gradient-based image noise level estimation method. The method comprises the steps of (1) dividing a noised image to be subjected to noise level estimation into a plurality of image blocks fixed in size; (2) calculating a comprehensive gradient measurement value of each pixel in each image block, and selecting a predetermined number of the image blocks according to interval distribution of comprehensive gradient measurement values; (3) performing de-noising on each selected image block by utilizing a neural network and calculating a variance value before and after de-noising; and (4) selecting a minimum variance value as a final image noise level estimation value. According to the method, the corresponding image block with relatively weak texture is selected in an image gradient statistics manner, so that the calculation precision of the final variance is improved; and by utilizing the neutral network, the selected image block is de-noised at first and then the variance of the image block with a difference value is calculated, so that an algorithm is more robust and the application range is wider.

Description

technical field [0001] The invention relates to the field of computer image processing, in particular to a gradient-based image noise level estimation method. Background technique [0002] The rapid development of multimedia technology makes us live in a world full of digital images and videos. However, these images are often accompanied by noise when they are imaged due to factors such as electronic components and lighting conditions. Usually the noise we study is independent of the image itself and obeys the Gaussian distribution of additive noise. Many denoising algorithms use the variance of the noise as a priori knowledge for the denoising process, but obviously this is not suitable for practical production, so it is necessary to automatically calculate the noise level from the noisy image. [0003] In recent years, many noise level estimation algorithms have been proposed, including the use of wavelet transform and so on. The filtering-based method is used to denois...

Claims

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Application Information

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IPC IPC(8): G06T7/00G06T7/40
CPCG06T7/0002G06T2207/20081G06T2207/20084G06T2207/30168
Inventor 叶福军张根源
Owner ZHEJIANG UNIVERSITY OF MEDIA AND COMMUNICATIONS
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