基于对比度敏感度的无参考图像清晰度评价

Abstract

A no reference image sharpness assessment method based on the property of Contrast Sensitivity Function(CSF) was proposed to realize the sharpness assessment of optical measurement equipment without reference television images.Firstly,a reference image for an original was constructed by a low-pass filter and both images were performed the Discrete Cosine Transform(DCT),and intermediate frequency coefficients and high frequency coefficients are divided into two parts respectively to be performed the Inverse DCT(IDCT) to obtain sub-images.Then,the Structural Similarity(SSIM) of corresponding sub-images was calculated.Finally,the image sharpness is obtained through the weighted sum of sub-image structural similarities.The experiment results show that the proposed method can obtain the Pearson Correlation Coefficient(CC) in 0.915 2,Spearman Rank Order Correlation Coefficient CC(SROCC) in 0.907 9 and out Rate(OR) in 0.034 5,which shows very high accuracy,monotonicity and consistency for the Gaussian blur image.The smallest defocus image can be quickly and accurately identified in the sequence defocus images and the effect is better than those of other four traditional focus evaluation functions.For different types of television blur images,the assessment results is more accord with human visual characteristics.It can be applied to optical measurement equipment television system and give accurate and reliable sharpness assessment of no reference television image.