共查询到20条相似文献,搜索用时 156 毫秒
1.
We extend the well-known scalar image bilateral filtering technique to diffusion tensor magnetic resonance images (DTMRI). The scalar version of bilateral image filtering is extended to perform edge-preserving smoothing of DT field data. The bilateral DT filtering is performed in the Log-Euclidean framework which guarantees valid output tensors. Smoothing is achieved by weighted averaging of neighboring tensors. Analogous to bilateral filtering of scalar images, the weights are chosen to be inversely proportional to two distance measures: The geometrical Euclidean distance between the spatial locations of tensors and the dissimilarity of tensors. We describe the noniterative DT smoothing equation in closed form and show how interpolation of DT data is treated as a special case of bilateral filtering where only spatial distance is used. We evaluate different recent DT tensor dissimilarity metrics including the Log-Euclidean, the similarity-invariant Log-Euclidean, the square root of the J-divergence, and the distance scaled mutual diffusion coefficient. We present qualitative and quantitative smoothing and interpolation results and show their effect on segmentation, for both synthetic DT field data, as well as real cardiac and brain DTMRI data. 相似文献
2.
In this paper, we introduce two novel techniques for digital color halftoning with green-noise-stochastic dither patterns generated by homogeneously distributing minority pixel clusters. The first technique employs error diffusion with output-dependent feedback where, unlike monochrome image halftoning, an interference term is added such that the overlapping of pixels of different colors can be regulated for increased color control. The second technique uses a green-noise mask, a dither array designed to create green-noise halftone patterns, which has been constructed to also regulate the overlapping of different colored pixels. As is the case with monochrome image halftoning, both techniques are tunable, allowing for large clusters in printers with high dot-gain characteristics, and small clusters in printers with low dot-gain characteristics. 相似文献
3.
Color error-diffusion halftoning 总被引:1,自引:0,他引:1
《Signal Processing Magazine, IEEE》2003,20(4):51-58
Grayscale halftoning converts a continuous-tone image (e.g., 8 bits per pixel) to a lower resolution (e.g., 1 bit per pixel) for printing or display. Grayscale halftoning by error diffusion uses feedback to shape the quantization noise into high frequencies where the human visual system (HVS) is least sensitive. In color halftoning, the application of grayscale error-diffusion methods to the individual colorant planes fails to exploit the HVS response to color noise. Ideally the quantization error must be diffused to frequencies and colors, to which the HVS is least sensitive. Further it is desirable for the color quantization to take place in a perceptual space so that the colorant vector selected as the output color is perceptually closest to the color vector being quantized. This article discusses the design principles of color error diffusion that differentiate it from grayscale error diffusion, focusing on color error diffusion halftoning systems using the red, green, and blue (RGB) space for convenience. 相似文献
4.
In real-world environments, the human visual system perceives a wide range of luminance in a scene. However, the full range of tones in a high dynamic range (HDR) scene cannot be displayed on standard display devices due to their low dynamic range (LDR). Therefore, tone mapping is necessary to faithfully display a HDR scene on an LDR display device. Existing tone mapping methods have problems because details and contrast in a scene are not preserved faithfully, and they also distort the colors in a scene. Thus, we propose a tone mapping method for preserving the detail in an HDR scene using a weighted least squares filter, which preserves the global contrast in a scene by using a competitive learning neural network, before applying a tone reproduction operator to preserve the color without shifting the lightness. According to the Helmholtz–Kohlrausch effect, the perception of brightness depends on the lightness, chroma, and hue of a color. For example, the luminance of pixels with specific colors such as red and blue is low in an HDR scene. The proposed method corrects the lightness of pixels according to the color (i.e., lightness, chroma, and hue) of a tone-mapped image. Experimental results with several test sets of images demonstrated that the proposed tone mapping method with contrast preservation and lightness correction is more suitable for dynamic range compression than existing tone mapping methods, while it also preserves the color of a scene in an effective way. 相似文献
5.
Fuzzy image clustering incorporating spatial continuity 总被引:4,自引:0,他引:4
Liew A.W.C. Leung S.H. Lau W.H. 《Vision, Image and Signal Processing, IEE Proceedings -》2000,147(2):185-192
The authors present a spatial fuzzy clustering algorithm that exploits the spatial contextual information in image data. The objective functional of their method utilises a new dissimilarity index that takes into account the influence of the neighbouring pixels on the centre pixel in a 3×1 window. The algorithm is adaptive to the image content in the sense that influence from the neighbouring pixels is suppressed in nonhomogeneous regions in the image. A cluster merging scheme that merges two clusters based on their closeness and their degree of overlap is presented. Through this merging scheme, an `optimal' number of clusters can be determined automatically as iteration proceeds. Experimental results with synthetic and real images indicate that the proposed algorithm is more tolerant to noise, better at resolving classification ambiguity and coping with different cluster shape and size than the conventional fuzzy c-means algorithm 相似文献
6.
《AEUE-International Journal of Electronics and Communications》2008,62(1):63-67
This paper proposes a robust approach to color image noise removal that efficiently eliminates noisy pixels by exploiting several vector-class characteristics of multichannel pixels. This algorithm treats multichannel images as a vector class and takes both magnitude and phase angles of the pixel vectors into consideration. It consists of two steps: an efficient noise detector based on pixel vector angle statistics and impulse noise filtering with a hybrid of vector magnitude and vector angle function. Extensive experimental results demonstrate that the proposed approach significantly outperforms several other well-known techniques for color image noise removal. 相似文献
7.
8.
为了解决当前图像伪造定位技术因使用了CFA 插值,易形成颜色插值噪声而降低分辨率,导致其难以检测微小篡改区域,使其伪造检测精度较低等不足,本文提出了像素预测误差耦合似然映射的图像伪造检测算法。首先,分析颜色滤波阵列CFA插值模型,并从图像中提取绿色分量;随后,嵌入权重因子,构造预测误差及其权重方差计算模型;根据预测误差与贝叶斯理论,定义伪造特征统计模型,识别出趋于零的特征值;最后,根据特征统计模型,建立其似然率模型,输出伪造映射,完成检测。仿真结果表明:与当前图像伪造定位机制相比,本文算法拥有更强的鲁棒性,能识别定位出微小伪造像素;且拥有更高的AUC值与理想的ROC曲线。 相似文献
9.
在对整幅图像色彩传递算法的基础上,提出了确定区域的人脸彩色传递法。首先利用改进的主动形状模型(ASM)方法定位人脸特征点,进而利用区域生长法确定人脸区域。在将参考图像和目标图像(彩色或灰度图)转换到去相关的对立色空间(lαβ颜色空间)后,对于彩色目标图像,分别调整肤色区域图各通道的均值和标准差;对于灰度目标图像,用亮度邻域统计量匹配的方法在参考图像中选取匹配点,并将匹配点的颜色赋值给目标图像中的对应点。最后,把传递结果转换到RGB颜色空间显示。实验结果表明,该方法能有效传递肤色,形成自然逼真的彩色人脸图像。 相似文献
10.
单CCD/CMOS 传感器相机捕捉图像信息靠在传感器表面覆盖一层颜色滤波阵列(CFA),经过CFA 后每个像素点只能获得物理三基色(红,绿,蓝)其中一种分量。另外缺少的两种颜色分量,需要通过周围像素的值来估算。首先利用55 模板内的像素来估计插值的方向并用最优的权重系数来插值G 分量。其次利用了基于有理函数的二维插值算子在色差空间插值R(B)处缺少的B(R)分量。再次利用色差插值G 处缺少的R 和B 分量。最后,使用方差约束条件,迭代插值过程被重复多次直到达到了最优的插值结果。通过在24 幅柯达图片以及笔者相机拍摄的图片上的Matlab 仿真实验,结果显示,被提出的算法无论是在视觉方面还是在量化的数据方面都表现出了优势。 相似文献
11.
12.
Moreno J.F. Gandia S. Melia J. 《Geoscience and Remote Sensing, IEEE Transactions on》1992,30(5):1006-1014
Information available from ephemeris data, combined with a few ground control points, is used to carry out the geometric combination of NOAA, AVHRR, and SPOT images by means of orbital models for each satellite. The observation conditions are reconstructed and the areas observed in common determined in the SPOT image pixels and each low-resolution AVHRR pixel. The determination of effective parameters, at low spatial resolution, from high-spatial-resolution data takes into account overlapping effects between adjacent pixels, and pixel size and shape variations with viewing angle for AVHRR data. The method is applied to surface temperature mapping of a selected heterogeneous area by incorporating NOAA AVHRR thermal data in a high-spatial-resolution emissivity map derived from SPOT data 相似文献
13.
Perceptual color correction through variational techniques. 总被引:3,自引:0,他引:3
Marcelo Bertalmío Vicent Caselles Edoardo Provenzi Alessandro Rizzi 《IEEE transactions on image processing》2007,16(4):1058-1072
In this paper, we present a discussion about perceptual-based color correction of digital images in the framework of variational techniques. We propose a novel image functional whose minimization produces a perceptually inspired color enhanced version of the original. The variational formulation permits a more flexible local control of contrast adjustment and attachment to data. We show that a numerical implementation of the gradient descent technique applied to this energy functional coincides with the equation of automatic color enhancement (ACE), a particular perceptual-based model of color enhancement. Moreover, we prove that a numerical approximation of the Euler-Lagrange equation reduces the computational complexity of ACE from theta(N2) to theta(N log N), where N is the total number of pixels in the image. 相似文献
14.
15.
Chun-Ming Tsai Hsi-Jian Lee 《IEEE transactions on image processing》2002,11(4):434-451
This paper presents a novel binarization algorithm for color document images. Conventional thresholding methods do not produce satisfactory binarization results for documents with close or mixed foreground colors and background colors. Initially, statistical image features are extracted from the luminance distribution. Then, a decision-tree based binarization method is proposed, which selects various color features to binarize color document images. First, if the document image colors are concentrated within a limited range, saturation is employed. Second, if the image foreground colors are significant, luminance is adopted. Third, if the image background colors are concentrated within a limited range, luminance is also applied. Fourth, if the total number of pixels with low luminance (less than 60) is limited, saturation is applied; else both luminance and saturation are employed. Our experiments include 519 color images, most of which are uniform invoice and name-card document images. The proposed binarization method generates better results than other available methods in shape and connected-component measurements. Also, the binarization method obtains higher recognition accuracy in a commercial OCR system than other comparable methods. 相似文献
16.
17.
Chen-Kuei Yang Ja-Chen Lin Wen-Hsiang Tsai 《Communications, IEEE Transactions on》1997,45(12):1513-1516
A new color image compression technique based on moment-preserving and block truncation coding is proposed. An input image is divided into nonoverlapping blocks and each block pixel is assigned one of two representative colors, which are computed with analytic formulas derived from preserving certain moments in the block. A bit map is then generated for each block to represent the pixels' colors. Different uniformity conditions in the representative colors are also identified and utilized to save code bits. Good average compression ratios up to about 13 can be achieved, as shown by experimental results 相似文献
18.
19.
Biologically Inspired Feature Manifold for Scene Classification 总被引:2,自引:0,他引:2
Dongjin Song Dacheng Tao 《IEEE transactions on image processing》2010,19(1):174-184
Biologically inspired feature (BIF) and its variations have been demonstrated to be effective and efficient for scene classification. It is unreasonable to measure the dissimilarity between two BIFs based on their Euclidean distance. This is because BIFs are extrinsically very high dimensional and intrinsically low dimensional, i.e., BIFs are sampled from a low-dimensional manifold and embedded in a high-dimensional space. Therefore, it is essential to find the intrinsic structure of a set of BIFs, obtain a suitable mapping to implement the dimensionality reduction, and measure the dissimilarity between two BIFs in the low-dimensional space based on their Euclidean distance. In this paper, we study the manifold constructed by a set of BIFs utilized for scene classification, form a new dimensionality reduction algorithm by preserving both the geometry of intra BIFs and the discriminative information inter BIFs termed Discriminative and Geometry Preserving Projections (DGPP), and construct a new framework for scene classification. In this framework, we represent an image based on a new BIF, which combines the intensity channel, the color channel, and the C1 unit of a color image; then we project the high-dimensional BIF to a low-dimensional space based on DGPP; and, finally, we conduct the classification based on the multiclass support vector machine (SVM). Thorough empirical studies based on the USC scene dataset demonstrate that the proposed framework improves the classification rates around 100% relatively and the training speed 60 times for different sites in comparing with previous gist proposed by Siagian and Itti in 2007. 相似文献
20.
应用于LCD控制器的动态抖动算法及帧速率控制技术 总被引:3,自引:2,他引:1
文章提出了应用于液晶显示(LCD)控制器的动态抖动算法及帧速率控制技术。抖动算法极大的改善了显示图象的平滑度,帧速率控制技术大大增加图象灰度而明显降低图象的抖动和赝象。结果显示在LCD控制器中采用动态抖动算法及帧速率控制技术,如果每一象素数据的位宽是8比特,则单色图象的显示效果可高达256级灰度,彩色图象高达256^3彩色。 相似文献