共查询到20条相似文献,搜索用时 109 毫秒
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本文提出了一种基于抖动和混沌技术的数字图像篡改检测及修复算法.该算法使用小波变换后的低频子图和抖动技术生成图像的认证及修复信息,在有效减少水印数据量的同时,将水印嵌入小波变换后的高频子图,从而达到水印的不可见性.运用混沌技术完成水印的嵌入和加密,并结合中国余数定理,进一步减少水印嵌入对图像质量的影响.实验证明,该算法兼顾了水印的不可见性和鲁棒性,并且能够一定程度修复篡改图像,在图像认证和修复方面具有较高的实用意义. 相似文献
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基于图像熵的高动态范围场景的自动曝光算法 总被引:2,自引:0,他引:2
自动曝光控制是通过控制曝光量使图像亮度最优化的过程,由于图像亮度与曝光值有着直接的关系,因而图像亮度在自动曝光算法中被广泛应用.虽然熵已用于各种图像处理应用,但是很少应用在自动曝光中.基于图像熵提出一种新的自动曝光算法,不同于传统的主要依赖于图像亮度的算法.首先根据图像熵值大小来判断光照条件,通过图像熵大小的比较,把图像的各区域划分为感兴趣区域与不感兴趣区域.然后由图像熵值大小采用分配权重方法对不同区域分配权重,最后进行准确地自动曝光.由于该算法主要基于图像熵值的大小,所以曝光效果不受图像中对象位置影响,使得该算法更灵活.实验结果表明,该算法对高动态范围场景可以准确地检测出各种光照条件,提高相机系统输出图像的动态范围,同时还增加了自动曝光的准确性. 相似文献
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Ching-Sheng Hsu 《Optics Communications》2010,283(9):1737-108
In recent years, digital watermarking technology has been widely used for property rights protection and integrity authentication of digital images. Image integrity authentication is usually done by a fragile watermarking scheme. When authenticating image integrity, one must extract the embedded authentication message from the image for comparison with the image feature to identify whether the image has been tampered with, and if so, locate the affected area. However, such authentication schemes may result in detection error problems. Namely, the tampered area may be misjudged as not having been tampered with, or vice versa. Hence, methods that effectively reduce errors in tampering detection have become an important research topic. This study aims to integrate a probability theory to improve image tampering detection accuracy and precision. The scheme includes two processes: the embedding of an image authentication message and tampering detection. In the image tampering detection process, in addition to identifying whether the image has been tampered with and locating the tampered area, through the authentication message embedded in the image, a probability theory is employed to improve previously obtained detection results to enhance authentication accuracy. The experimental results reveal that the proposed scheme performs well in terms of detection precision and authentication accuracy rate. 相似文献
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Yeh-Shun Chen 《Optics Communications》2011,284(12):2711-108
This paper presents an image authentication scheme for digital images. The proposed scheme protects a group of n images mutually. It designs a block matching procedure to generate the recovery data for each image, and applies a (t, n − 1), 2 ≤ t < n, threshold mechanism to encode each recovery data in n − 1 shares. The recovery shares are cross-embedded in the n images using a modified reversible contrast mapping watermarking scheme. A signature-based authentication code is finally generated and stamped to provide evidence for integrity of each image. The scheme not only can detect the tampering activities, but also can locate and recover the invalid regions of the tampered image if t or more watermarked images in the same group were intact. A nice characteristic of the proposed scheme is that the original images can be reconstructed lossless if no watermarked image was tampered, making the technique feasible in the application of protecting very sensitive images such as military or medical images. Experimental results show that the proposed scheme successfully detects various kinds of image alterations such as filtering, cropping, and replacement, and the corrupted images are properly recovered using the cross-recovery scheme. 相似文献
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To take invisibility and restoration quality into account, this paper proposes an alterable-capacity watermarking scheme. For each block of size 8 × 8 pixels, the alterable-length code is generated based on the roughness of it. The alterable-length watermark generated by the alterable-length code is divided into three parts and embedded in other three blocks based on the secret key. The authenticity of each block is determined by comparing the watermark reconstructed by the block content and the corresponding extracted watermark. To improve the quality of recovered images, two copies of the significant-code of each block are embedded in different blocks and the image inpainting method is adopted to recover the tampered blocks whose significant-code embedded in other blocks is destroyed. The alterable-payload watermark preserves adequate information of image blocks especially for texture images with as few bits as possible and takes into account invisibility, security and restoration quality. Experimental results demonstrate that the proposed scheme improves the quality of watermarked and reconstructed images and is resilient to the known forgery attacks. 相似文献
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Video cameras have been widely installed in public facilities for the surveillance applications. So, video authentication has becoming increasingly attractive. This paper presents a dual watermarking for video authentication based on moving objects. For each frame, the frame index, as a watermark is first embedded into the moving objects of the corresponding frame using a reversible watermarking method, aiming to detect the temporal tampering. Then the principle content and the details of the moving objects combined with the authentication code, as the other watermark, are embedded into the frame for spatial tampering location and recovery. Specially, a synthesized frame method is proposed for lossless recovery of moving objects and effective extraction of frame index. Statistical analysis and experiment results show that the proposed method can locate spatial, temporal and spatio-temporal tampering accurately. The spatial tampered regions can be recovered approximately and the moving objects can be restored completely when the tampered area is limited. 相似文献
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The rapid development of multimedia technology has resulted in a rising rate on digital unauthorized utilization and forgery, which makes the situation of image authentication increasingly severe. A novel strong image hashing scheme is proposed based on wave atom transform, which can better authenticate images by precisely distinguishing the malicious tampered images from the non-maliciously processed ones. Wave atom transform is employed since it has significantly sparser expansion and better characteristics of texture feature extraction than other traditional transforms. For better detection sensitivity, gray code is applied instead of natural binary code to optimize the hamming distance. Randomizations are also performed using Rényi chaotic map for the purposes of secure image hashing and key sensitivity. The experimental results show that the proposed strong scheme is robust to non-malicious content-preserving operations and also fragile to malicious content-altering operations. The scheme also outperforms DCT and DWT based schemes in terms of receiving operating characteristic (ROC) curves. Moreover, to provide an application-defined tradeoff, a security enhancement approach based on Rényi map is presented, which can further protect the integrity and secrecy of images. 相似文献
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A method of obtaining ultrasonic images of objects radiating ultrasonic acoustic waves in the air is proposed. Object images are retrieved by spatially matched filtering of the amplitude-phase distribution of the ultrasonic field measured in a planar rectangular region at a distance from the radiating object under investigation. The field is measured at different frequencies in a wide band, which allows one to reduce the level of noise and artifacts in the retrieved images by processing in a wide frequency band. 相似文献
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为在足球视频中有效的检测与跟踪运动目标,需要对足球比赛视频中目标检测与跟踪算法进行研究。当前采用的算法,在动态场景中,存在运动目标检测与跟踪效果不佳的问题。为此,提出一种基于OpenCV的足球比赛视频中目标检测与跟踪算法。该算法结合平均背景算法将足球比赛视频中目标图像分割为前景区与背景区,计算足球比赛视频每一帧目标图像和背景图像之间差值的绝对差值,同时计算每一个目标图像中像素点的平均值与标准值来建立目标图像背景统计模型,利用TMHI算法对足球比赛视频中目标初始图像进行阈值分割,得到初始分割图像,对分割图像进行中值滤波和闭运算,再使用卡尔曼滤波对分割后的目标图像进行处理,得到镜头中目标的质心位置和目标外界矩形框,然后对足球比赛视频中目标进行跟踪。实验证明,该算法有效的检测与跟踪足球视频中运动目标。 相似文献
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The band artifact in steady-state free precession can be reduced by synthesizing the multiple images obtained through different phase increments of successive radiofrequency pulses. Even though the complex summation method was reported to be effective in reducing the band artifact, it has the pitfalls of intensity abnormality and sensitivity to the phase abnormality. Two new methods have been developed for more reliable reduction of the band artifact than the complex summation method. One method is to sum the complex images partially and to take the maximum intensity of the partially summed images. The other method is to sum the free induction decay (FID) and primary echo components of the Fourier series that are obtained through Fourier analysis of the complex base images. Both proposed methods were compared with other magnitude (maximum intensity projection, spectrally decomposed synthesis, sum-of-squares, nonlinear averaging) and complex-based (complex summation, magnitude-weighted complex summation) methods experimentally at 3 T for the phantom and volunteer's head imaging. Both proposed methods were confirmed to maintain the advantage of the complex summation in reducing both the dark and bright band artifacts while reducing the intensity abnormality and sensitivity to the phase abnormality from that of the complex summation method over a wide range of flip angles and relaxation times. 相似文献