Image tone adjusting method based on cordic algorithm

Abstract

The invention discloses a method for adjusting image tone by using a cordic algorithm, which comprises the following steps: 1) initializing an image and obtaining the red color difference Cr and the blue color difference Cb of the original image and tone angle theta, wherein Cb' equals to Cb cosine theta plus Cr sine theta, and Cr equals to Cr cosine theta minus Cb sine theta; 2) using the cordicalgorithm to calculate the relation between the adjusting angle theta and a rotating factor delta i, thus determining the values of delta i of all orders of the image data, namely, gamma equals to sigma delta i gamma i equals to sigma delta i tangent<-1>(2<-i>), wherein gamma equals to minus delta; and 3) conducting displacement operation according to the values of delta i of all orders of the image data: first calculating and obtaining the characters on all orders of the delta i according to the adjusted tone angle of the image; then conducting displacement operation to all orders of image tone information data from the lowest order, selecting according to the characters of all orders, if the character has plus sign, keeping it unchanged, and if the character has minus sign, negating thedata on the order; and finally, after the displacement of the highest order, obtaining the output result of the operation, which is the final data of tone adjusting result. The method simplifies multiplication, reduces the complexity of calculation, and improves the calculation accuracy simultaneously.

Description

technical field [0001] The invention relates to a method for adjusting image tone, specifically, a technique for adjusting image tone by using a cordic algorithm. Background technique [0002] Hue control generally follows the function For processing, here [Cb Cr] and [Cb'Cr'] are color difference signals before and after processing, and θ represents the desired hue angle. The value range of θ is (-180°, 180°), and the typical 8-bit hue adjustment range is (-30°, 30°). The calculation of the hue adjustment needs to use the calculation of the sin and cos values, which cannot be accurately calculated by hardware. The common method in the industry is to use the look-up table method to directly look up the corresponding sin and cos from the hue adjustment angle θ value. However, the accuracy of this algorithm is limited, and it will consume additional storage space, affecting the final chip area. In the process of adjusting the saturation, a relatively accurate adjustment e...

AI Technical Summary

Problems solved by technology

The calculation of the hue adjustment needs to use the calculation of sin and cos values, which cannot be accurately calculated by hardware. The common method in the industry is to use the look-up table method to directly look up the corresponding sin and cos from the hue adjustment angle θ value

However, the accuracy of this algorithm is limited, and it will consume additional storage space, affecting the final chip area

In the process of adjusting the saturation, a more accurate adjustment effect is required, and here due to the limited accuracy, errors will be introduced, which will affect the adjustment results

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