基于细分的图像插值算法

将基于法向的曲线细分技术应用到图像插值中，提出一种基于细分的图像插值算法．该算法无须建立中间连续图像模型，能自适应地插值，而且插值系数可为任意正实数．应用该算法插值后的边界清晰、自然，忠实地反映了原始图像的面貌．与传统的插值算法相比，其边界处理效果好，具有线性复杂度且易于实现．     

Optimised coupling of hierarchies in image registration

Image registration algorithms rely on multilevel strategies in order to improve efficiency and robustness. Hierarchies in image resolution, the underlying grids for spline-based transformations, as well as the regularisation parameters are used. This paper deals with the optimisation of the coupling of these hierarchies.

An image registration procedure – suitable for 2D polyacrylamide gel electrophoresis images – using piecewise bilinear transformations and an intensity based objective function with a regularisation term based on the elastic deformation energy is described. The resulting nonlinear least squares problem is solved by the Gauss–Newton method.

Techniques reminiscent of dynamic programming are used to optimise the coupling of hierarchies in image and transformation resolution. Besides using these techniques to devise an advantageous fixed coupling of both hierarchies, we favour incorporating the dynamic programming ideas into the final registration algorithm. This leads to an adaptive and streamlined approach.

Numerical experiments on 2D-PAGE images show that the adaptive registration algorithm is much more reliable than the same algorithm with a fixed coupling of hierarchies. The proposed optimisation procedure for the coupling of hierarchies presents a valuable tool to optimise other registration algorithms.     

Observations on complete sets between linear time and polynomial time

There is a single set that is complete for a variety of nondeterministic time complexity classes with respect to related versions of m-reducibility. This observation immediately leads to transfer results for determinism versus nondeterminism solutions. Also, an upward transfer of collapses of certain oracle hierarchies, built analogously to the polynomial-time or the linear-time hierarchies, can be shown by means of uniformly constructed sets that are complete for related levels of all these hierarchies. A similar result holds for difference hierarchies over nondeterministic complexity classes. Finally, we give an oracle set relative to which the nondeterministic classes coincide with the deterministic ones, for several sets of time bounds, and we prove that the strictness of the tape-number hierarchy for deterministic linear-time Turing machines does not relativize.     

基于视觉注意力和局部复杂性的图像隐写算法

视觉注意力是人类感知系统中一个十分重要的特性,但目前基于人类视觉感知机理的隐写算法大多只考虑亮度、对比度和掩蔽效应等低层因素.文中将视觉注意力模型引入隐写算法中,提出一种新的基于视觉注意力和局部复杂性的图像隐写算法.算法先采用均方差分析图像的局部复杂性,在复杂性较大的区域引入Itti模型构造注意力显著图,进而利用视觉熵来定量刻画注意力特性,并将图像分块处理,图像块按照不同的局部复杂程度和注意力等级分成3种类型,最终利用LSB方法进行隐写.大量实验结果表明,文中算法在嵌入大量信息后仍能保持较好的视觉感知效果,且能抵抗一类通过直方图对比的隐写分析方法.     

基于边缘的实时图像缩放算法研究

传统的基于图像边缘的插值算法由于自身的复杂性而很少用于实时图像处理,而不基于边缘的插值算法由于低通滤波的效应通常会使插值后的图像出现边缘模糊,影响视觉效果。针对上述问题,提出了一种基于边缘的自适应图像插值算法。该算法以相邻像素的二阶差分为基础,自动选择与目标像素点相对应的源像素组进行插值运算。在Matlab环境中实现了各种图像插值算法,然后对插值结果进行了主客观评价,并对各种算法获得的图像进行了边缘检测及复杂度分析。同时,设计了本文算法的硬件实现结构,并用Verilog语言进行描述,综合出目标代码,最后通过FPGA验证。研究表明,运用该算法插值获得了边缘清晰的目标图像,且该算法复杂度低,便于硬件实现。因此,该算法能有效地实现图像插值,适应于实时条件下的图像缩放。     

基于放缩系数和均值的多参数颜色迁移

彩色图像间的颜色迁移在图像处理和数字娱乐领域具有重要应用。为增加颜色迁移效果的多样性,研究了颜色迁移的本质,并在 Reinhard 算法的基础上,提出了基于放缩系数和均值的多参数颜色迁移方法,不仅对放缩系数给出了多种选取方式,而且将原来单一的参考图像的均值改为原图像均值和参考图像均值按一定比例搭配的数值,最终使得原图像经过颜色迁移后可生成多种结果图像,以供用户根据不同的喜好选择不同的视觉效果。然后将其推广到多幅图像之间的颜色类比问题。最后通过若干实例验证了本文方法的有效性。     

彩色图像分形维数的计算方法

分形维数是描述图像复杂性的一种重要测度,广泛应用于图像特征提取及图像分类、分割和检索等方面。多种黑白图像和灰度图像的分形维数计算方法已被提出,但其中很少有适用于彩色图像的分形维数计算方法。把计算灰度图像分形维数的差分盒维法扩展到欧氏五维空间,提出了一种简单且易实现的计算彩色图像分形维数的方法。实验结果表明,提出的方法能够捕捉到彩色图像纹理的复杂性,在识别彩色图像粗糙度变化和计算精度方面优于其它算法。     

Hierarchical image analysis using irregular tessellations

A novel multiresolution image analysis technique based on hierarchies of irregular tessellations generated in parallel by independent stochastic processes is presented. Like traditional image pyramids these hierarchies are constructed in a number of steps on the order of log(image-size) steps. However, the structure of a hierarchy is adapted to the image content and artifacts of rigid resolution reduction are avoided. Two applications of these techniques are presented: connected component analysis of labeled images and segmentation of gray level images. In labeled images, every connected component is reduced to a separate root, with the adjacency relations among the components also extracted. In gray level images the output is a segmentation of the image into a small number of classes as well as the adjacency graph of the classes