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1、0,任爱锋 电子工程学院 E-mail: Office: 新科技楼A901 Phone: 88202830-607 Mobile: 13384919599,Unit 11,Digital Image Processing,Part I,Two-Dimensional Digital Images,3,New Words,4,New Words,5,1,Images are two-dimensional signals representing spatial distribution of some physical parameters, typically light intensit
2、y, and more generally any form of energy. Motion pictures and multi-spectral remote sensing images, for example, are three or higher dimensional signals.,图像是表示一些物理参数空间分布的二维信号，典型的物理参数是光强，而更普通的是能量的任一种形式。例如，运动图像以及多光谱的遥感图像是三维或者是更高维的信号。,6,1,Modern digital technology has made it possible to manipulate mul
3、ti-dimensional signals with systems that range from simple digital circuits to advanced parallel computers.1,现代数字技术使得处理多维信号成为可能，所使用的系统可从简单的数字电路到先进的并行计算机。,7,1,The goal of this manipulation can be divided into three categories: Image processing: image in image out Image analysis: image in measurements
4、 out Image understanding: image in high-level description out,这种处理的目的可以分为3类： - 图像处理：输入图像输出图像 - 图像分析：输入图像输出测量数据 - 图像理解：输入图像输出高层次的图像描述,8,2,We will focus on the fundamental concepts of image processing. Space does not permit us to make more than a few introductory remarks about image analysis and image
5、 understanding. Further, we will restrict ourselves to two-dimensional (2D) image processing although most of the concepts and techniques that are to be described can be extended easily to three or more dimensions.2,我们将介绍的重点集中在图像处理的基本概念上。篇幅所限，我们只能对图像分析以及图像理解进行一些介绍性的说明。另外我们将限于讨论二维图像处理，尽管将要描述的大部分概念和方法
6、很容易扩展到三维或更高的维数。,9,3,We begin with certain basic definitions. An image defined in the “real world” is considered to be a function of two real variables, for example, a(x, y) with a as the amplitude (e.g. brightness) of the image at the real coordinate position (x, y). An image may be considered to co
7、ntain sub-images sometimes referred to as regions-of-interest, ROIs, or simply regions. This concept reflects the fact that images frequently contain collections of objects each of which can be the basis for a region.,我们从一些基本定义开始。在“真实世界”中定义的一幅图像可以看成是两个实变量的函数，例如：以a作为在实坐标位置(x, y)处幅度（亮度）的图像a(x, y)。一幅图像
8、可以看成是包含许多子图像，这些子图有时称之为感兴趣区域，ROI，或者仅仅是图像中的区域。这一概念表明图像通常包含许多对象，每一个对象可以是一个区域的主要部分。,10,3,In a sophisticated image processing system it should be possible to apply specific image processing operations to selected regions. Thus one part of an image might be processed to suppress motion blur while another
9、part might be processed to improve color rendition.3,在一个复杂的图像处理系统中，应该能对于选择的区域进行特定的图像处理运算。于是图像的一部分可以进行抑制运动模糊的处理，而另一部分可以作改进色彩渲染的处理。,11,4,The amplitudes of a given image will almost always be either real numbers or integer numbers. The latter is usually a result of a quantization process that converts
10、a continuous range, say, between 0 and 100%, to a discrete number of levels.4,一幅给定图像的幅度几乎总是要么是实数，要么是整数。后者通常是量化的结果，将一个连续的范围如0到100%转换为离散的（灰度）级。,12,4,In certain image-forming processes, however, the signal may involve photon counting which implies that the amplitude would be inherently quantized. In ot
11、her image forming procedures, such as magnetic resonance imaging, the direct physical measurement yields a complex number in the form of a real magnitude and a real phase. We will consider amplitudes as reals or integers unless otherwise indicated.,然而，在某些图像形成过程中，信号可能涉及到光子计数，这意味着幅度本来是量化的。其它的图像形成过程，如磁
12、共振成像，直接的物理测量会产生一个复数，具有实的幅度和实的相位。除非另有说明，我们认为幅度是实数或者是整数。,13,5,A digital image am, n described in a 2D discrete space is derived from an analog image a(x, y) in a 2D continuous space through a sampling process that is frequently referred to as digitization.5,一幅二维离散空间中的数字图像am, n是由二维连续空间中的模拟图像a(x, y)通过采样
13、得到的。采样过程常称为数字化。,14,5,The mathematics of that sampling process will be described later. For now we will look at some basic definitions associated with the digital image. The effect of digitization is shown in Figure 11.1.,对采样过程的数学表示将在稍后介绍。现在，我们来看一些和数字图像有关的基本定义。图11.1显示了数字化的效果。,15,6,The 2D continuous i
14、mage a(x, y) is divided into N rows and M columns. The intersection of a row and a column is termed a pixel. The value assigned to the integer coordinates m, n with m = 0, 1, 2, . , M1 and n = 0, 1, 2, . , N1 is am, n.,2维连续图像a(x, y)被划分成N行M列。一行一列的交叉点被叫做一个像素。整数坐标m, n被赋予的值是am, n，其中：m = 0, 1, 2, . , M1
15、，n = 0, 1, 2, . , N1。,16,6,In fact, in most cases a(x, y), which we might consider to be the physical signal that impinges on the face of a 2D sensor, is actually a function of many variables including depth, color, and time.6 Unless otherwise stated, we will consider the case of 2D, monochromatic,
16、static images in this text.,实际上，大多数情况下，我们认为是射到二维传感器表面的物理信号a(x, y)实际上是许多变量的函数，包括深度、颜色、时间。除非另作说明，本文我们考虑的是2维的，单色的静止的图像情况。,17,7,The image shown in Figure 11.1 has been divided into N = 16 rows and M = 16 columns. The value assigned to every pixel is the average brightness in the pixel rounded to the nearest integer value.,图11.1的图像被划分成了N = 16 行以及M = 16列。赋予每个像素的值是像素的平均亮度，其四舍五入到最近的整数。,18,7,The process of representing the amplitude of the 2D signal at a given coordinate as an integer value with L different gray levels is usually referred to as amplitude quantization or simply quantization.7,
