基于最大意义位(MSB)的图像篡改认证算法

提出一种用于图像认证的半脆弱水印算法,该算法能够区分出恶意攻击和一般的图像处理.实验表明该算法能准确确定篡改的具体位置,同时对JPEG压缩等常规的图像操作具有较好的鲁棒性.这种算法以16×16个像素点为分块单位对图像进行分块认证,通过小波变换并采用SHA-256产生认证信息,再通过颜色量化的方法,把认证水印信息嵌入到图像的最大意义位,在水印的嵌入过程中,以块为单位对认证信息进行置乱后再进行嵌入,保证了认证的可靠性和水印的鲁棒性,有一定的抗攻击能力.     

A hierarchical digital watermarking method for image tamper detection and recovery

In this paper, we present an efficient and effective digital watermarking method for image tamper detection and recovery. Our method is efficient as it only uses simple operations such as parity check and comparison between average intensities. It is effective because the detection is based on a hierarchical structure so that the accuracy of tamper localization can be ensured. That is, if a tampered block is not detected in level-1 inspection, it will be detected in level-2 or level-3 inspection with a probability of nearly 1. Our method is also very storage effective, as it only requires a secret key and a public chaotic mixing algorithm to recover a tampered image. The experimental results demonstrate that the precision of tamper detection and localization is 99.6% and 100% after level-2 and level-3 inspection, respectively. The tamper recovery rate is better than 93% for a less than half tampered image. As compared with the method in Celik et al. [IEEE Trans. Image Process. 11(6) (2002) 585], our method is not only as simple and as effective in tamper detection and localization, it also provides with the capability of tamper recovery by trading off the quality of the watermarked images about 5 dB.     

一种具有高攻击类型判别能力的图像空域半脆弱水印算法

在考虑图像对比度特性的基础上,提出了一种图像空域半脆弱水印算法。算法由图像对比度敏感性确定各像素水印嵌入比特位,通过LSB(Least Significant Bit)替换方法自适应嵌入水印,从理论上推导出用于图像认证的篡改检测阈值。对图像对比度特性的充分考虑,可确保算法具有较好的透明性。实验表明,算法对可接受的偶然攻击操作具有一定的鲁棒性,同时对恶意攻击较为脆弱,并且能准确定位图像篡改区域。此外,算法能正确区分偶然攻击与恶意攻击,显示出比同类算法更好的攻击类型判别能力。     

An image authentication method by applying Hamming code on rearranged bits

In 2007, Chan and Chang proposed an image authentication method using the Hamming code technique. The parity check bits were produced from pixels by using the Hamming code technique, and the produced bits were embedded in other pixels. When recovering, the method had to predict the value of the most-significant bit of each tampered pixel first. Then, the tampered pixel was able to be recovered by referring to the predicted bit and its parity check bits. However, using the most-significant bit is unsuitable because of the risk of making an incorrect prediction. In this paper, the parity check bits are produced from pixels whose bits have been rearranged. This way, the value of the most-significant bit of each tampered pixel can be determined according to its parity check bits. The recovery procedure is also modified to accommodate the rearranging procedure. The experimental results show that the proposed method has a better ability to recover the tampered areas, compared with Chan and Chang’s method. Moreover, the quality of the authenticated images of the proposed method is also higher than that of Chan and Chang’s method.     

FPGA中实现Bayer模板双线性插值算法的改进

针对单板CMOS图像传感器采集的Bayer模板的数据,结合FPGA硬件结构FIFO_DFF构成3×3插值模板,提出一种改进的双线性插值算法.插值过程中利用当前要还原的分量同通道的水平、垂直以及两个对角线方向上的已知分量进行边缘检测,用梯度小的方向的分量进行插值还原缺失的分量.实验结果表明,在FPGA中使用该算法插值得到的图像色彩准确,增强了图像的边缘和细节,图像清晰度高.     

An efficient image authentication method based on Hamming code

Image authentication has come through a history of several years. However, up to the present time, most mainstream image authentication schemes are still unable to detect burst bit errors. Moreover, the capability of recovering tampered pixels in detail (complex) areas has not been very satisfactory either. In this paper, we offer to combine the Hamming code technique, Torus automorphism and bit rotation technique to do tamper proofing. According to our experimental results, our new hybrid method can effectively eliminate burst bit errors, and our recovered pixels in detail areas can actually gain very high clarity. The results show that our scheme is quite a practical method, which is quite able to detect and recover tampered areas.     

一种基于混沌映射的易碎水印

根据混沌系统良好的利值敏感性。提出了一种基干混沌系统的图像易碎水印方案。该方案对8x8图像块的直流能量和平均DCT系数进行混沌迭代产生易碎水印，该水印不仅保证了对篡改的敏感性，而且可以对攻击进行篡改定位。     

Color reconstruction in digital cameras: optimization for document images

Digital cameras normally sample one color at each pixel. Missing colors are obtained by spatial interpolation, decreasing resolution relative to images acquired with a greyscale sensor. The consequence for document imaging is higher text recognition error rates. This paper introduces the horizontal-vertical regression (HVR) method for document-optimized color reconstruction. HVR exploits a local two-color approximation, making spatial interpolation unnecessary. Comparison with the best alternative reconstruction methods indicates large reductions in error rates for text resulting from HVR, as well as improvements in intermediate color and binary images.Received: 11 June 2003, Accepted: 6 March 2004, Published online: 2 February 2005C. Dance: Correspondence to     

一种改进的Bayer图像彩色恢复差值算法

图像传感器采集到的都是经过滤波镜.片后的Bayer格式马赛克图像,为了恢复丢失掉的色彩信息,必须经过插值计算。针对图像采集系统处理的实时性要求,结合自适应插值法和三角函数法则,提出了一种适用于硬件实现的新算法。给出对算法性能的评估数据和MATLAB仿真图片,对比了算法的处理效果,最后基于实际应用的需求对该算法的硬件实现难度进行了分析。实验结果证明,改进算法在图像边缘的处理上效果更好,基于硬件的实现方式也能保证系统的实时性。     

A numerically stable fragile watermarking scheme for authenticating 3D models

This paper analyzes the numerically instable problem in the current 3D fragile watermarking schemes. Some existing fragile watermarking schemes apply the floating-point arithmetic to embed the watermarks. However, these schemes fail to work properly due to the numerically instable problem, which is common in the floating-point arithmetic. This paper proposes a numerically stable fragile watermarking scheme. The scheme views the mantissa part of the floating-point number as an unsigned integer and operates on it by the bit XOR operator. Since there is no numerical problem in the bit operation, this scheme is numerically stable. The scheme can control the watermark strength through changing the embedding parameters. This paper further discusses selecting appropriate embedding parameters to achieve good performance in terms of the perceptual invisibility and the ability to detect unauthorized attacks on the 3D models. The experimental results show that the proposed public scheme could detect attacks such as adding noise, adding/deleting faces, inserting/removing vertices, etc. The comparisons with the existing fragile schemes show that this scheme is easier to implement and use.     

Color filter array design using random patterns with blue noise chromatic spectra

We propose two new types of random patterns with R, G, B colors, which allow to design color filter arrays (CFAs) with good spectral properties. Indeed, the chrominance channels have blue noise characteristics, a property which maximizes the robustness of the acquisition system to aliasing. With these new CFAs, the demosaicking artifacts appear as incoherent noise, which is less visually disturbing than the moiré structures characteristic of CFAs with periodic patterns.     

一种用于数字图象传感器的彩色插值算法

由于物理结构的限制 ,单片 CCD和 CMOS彩色图象传感器在每个像素的位置上只能采集一个颜色分量 ,其余两个颜色分量只能通过插值的办法得到 .鉴于通常的线性插值方法容易使图象的边缘变得模糊 ,并可能出现较为明显的颜色失真 ,而一些新方法尽管可以得到较高质量的插值图象 ,然而运算的复杂性限制了它们的应用 .为此提出了一种在色差空间进行插值的算法 ,以代替普通颜色空间的插值 ,同时用基于有理函数的插值算子来代替普通的线性算子 ,并通过后处理来进一步提高插值图象的质量 .由于色差空间的插值考虑了不同颜色分量间的耦合性 ,并利用了有理函数插值算子固有的边缘自适应特性 ,因而得到了较好的效果 .该方法另外的一个优点是计算速度较快 .实验结果表明 ,该该算法是有效的 .     

A public fragile watermarking scheme for 3D model authentication

A public fragile watermarking scheme based on the sensitivity of vertex geometry is proposed for 3D model authentication. In the 3D fragile watermarking embedding, slightly perturbing the positions of a subset of vertices is usually needed to keep them in some predefined relationship with their neighboring vertices. Two problems frequently arise in the embedding stage: the causality problem and the convergence problem. The causality problem arises while the neighboring relationship of a former processed vertex is influenced by the perturbing of its latter processed neighboring vertices. The convergence problem means that the original model has been heavily distorted before some vertices reach the predefined relationship. In this paper, we propose a multi-function vertex embedding method and an adjusting-vertex method to overcome these two problems. The proposed method does not need the original model and watermarks for authentication; moreover, the key for extracting watermarks is relatively smaller than that of previous works. For some artistic or technical models, sometimes it is very important to control the distortion ratio caused by watermark embedding. Our method can control the average distortion by the keys used in watermark embedding. Experimental and analytic results on various kinds of 3D models show the effectiveness of the scheme.     

Visually lossless compression for Bayer color filter array using optimized Vector Quantization

Devices using single sensors to capture colour images are cheaper due to high cost of Charge Couple Device (CCD) sensors or Complementary Metal-Oxide Semiconductor (CMOS) sensors. Single sensor devices use Colour Filter Array (CFA) to sample one colour band at every pixel location. Demosaicking process is applied to interpolate the two missing colours from the surrounding. Typically compression is done on the demosaicked images which may not be efficient due to the individual compression of the different colour space. This work investigated compression of raw data before demosaicking and performs demosaicking to reconstruct the R, G, B bands later. A novel Vector Quantization (VQ) technique for encoding the wavelet decomposed image using Modified Artificial Bee Colony (ABC) optimization algorithm is proposed. The proposed technique is compared with Genetic Algorithm based VQ and ABC based quantization and with standard LBG and Lloyd algorithm. Results show higher Peak Signal-to-Noise Ratio (PSNR) indicating better reconstruction.     

Bayer阵列图像去马赛克算法综述

Bayer阵列图像去马赛克技术是对稀疏采样的Bayer阵列图像进行RGB信息重建,图像重建质量是成像设备评价的重要因素之一,同时也对其他计算机视觉任务(如图像分割、人脸识别)产生影响。随着深度学习方法的快速发展,图像去马赛克领域提出了多种高性能算法。为了便于研究者更全面了解图像去马赛克算法的原理和研究进展,本文对该领域的经典算法和深度学习算法进行综述。首先对Bayer采样阵列原理和图像去马赛克技术进行概述。然后将现有方法分为传统方法和基于深度学习方法两类进行总结,同时根据去马赛克任务是否具有独立性,将深度学习方法分为独立去马赛克任务和联合去马赛克任务两类,分析不同方法的原理和优缺点,重点阐述基于深度学习的去马赛克方法的网络结构和重建机理,介绍去马赛克领域常用的公共数据集和性能评价指标,并对图像去马赛克相关实验进行分析对比。最后,围绕网络深度、运算效率和实用性等方面分析了现阶段图像去马赛克技术面临的挑战及未来发展方向。目前,基于深度学习的图像去马赛克方法已成为主流发展方向,但仍然存在计算成本较高、实际应用性不强等问题。因此,如何开发出重建精度高、处理时间短以及实用性强的图像去马赛克方法,...     

基于Bayer滤镜的彩色图像复原方法

通过对非自适应的双线性插值法、平滑色调转换插值法、边缘检测插值法、基于模式识别的插值法等几种复杂的保边缘效果更好的插值算法进行应用比较和实验分析,建立了基于模式识别的自适应插值方法的图像边缘样本模型,该方法在匹配图像边缘的基础上进行自适应的插值,取得了最好的复原效果,从而证明了其在空间科学实验应用中的有效性.     

基于多梯度的区域自适应去马赛克算法*

针对Bayer格式的彩色滤波阵列,鉴于传统去马赛克算法存在图像纹理和边缘模糊的现象,提出了一种基于多梯度的区域自适应去马赛克算法.该算法利用区域水平和垂直方向的梯度组算子来判断区域平滑程度和插值方向,从而有效地恢复绿色分量,同时根据色度差恒定原理来还原另外两个丢失的颜色信息.实验结果显示,相对于传统插值算法提高了图像的峰值信噪比,锐化了图像的纹理和边缘,改善了图像的视觉质量.     

机械加工零件表面纹理缺陷检测

在一些对机械加工零件表面的加工精度和表面质量要求较高的自动化工业中,对机械加工零件表面纹理缺陷进行可靠的、有效的检测和分析可以大大地提高生产加工的自动化水平。为了能够对机械加工零件表面进行可靠、有效的检测,根据机械加工零件表面的纹理特点,设计了一种新的图像频域滤波器,用于增强缺陷纹理图像和抑制背景纹理对缺陷纹理检测的干扰,再通过图像分割的方法的实现了缺陷纹理和背景纹理的分割。实验结果显示,这种方法检测速度较快,尤其适用于机械精加工零件表面纹理缺陷的准实时检测。     

Single-sensor imaging in consumer digital cameras: a survey of recent advances and future directions

This paper surveys in a systematic way recent advances in single-sensor imaging. In particular, the most distinctive elements of a single-sensor imaging pipeline, such as color filter array configurations, image interpolation solutions, and picture storage approaches are reviewed and commented upon. New perspectives in the field are proposed, suggesting that the demand for consumer digital camera solutions and digital color imaging applications will continue.