Digital Image Processing - MATLAB-0

Gonzalez - Digital Image Processing MATLAB - Standing on the Shoulders of Giants - Study Notes

http://www.imageprocessingplace.com/

2.1
MATLAB Image Processing Toolbox IPT is a function set that expands the numerical computing capabilities of MATLAB. The image x and y coordinates and amplitudes are continuous, and the first step in digitization is digitization. The digitization of coordinate values is called sampling or sampling , and the digitization of amplitude is called quantization . The general image coordinate origin is (0, 0), and the image coordinate representation of Matlab's IPT toolbox is (1, 1). Stored in a matrix variable.
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2.2 The reading and display of images in Matlab are maintained

imread('fiilename');#不加分号会立即显示图像，加分号表示取消输出。
 #eg:f=imread('dog.png');
 size(f);#给出图像的行数和列数
 [M,N]=size(f);#获取行数和列数
 whos f#显示数组f的信息。
 imshow(f);#默认显示彩色图
 imshow(g);#再次用imshow会覆盖掉前面的f图像的显示，可以用figure函数取代
 figure,imshow(g);
 imshow(f,G);#显示图像f的灰度图
 imshow(f,[low,high]);#显示图像f的灰度图，小于low的显示为黑色，大于等于high的显示为白色，介于两者之间的显示为中等亮度值
 imwrite(f,'copyf.png');#保存图像
 imfinfo filename#显示图像文件信息
 k=imfinfo('dog.jpg');#图像信息保存到k中

2.2 The pixel value in the data class Matlab is not an integer,

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Brightness image
data matrix, the normalized value represents the brightness, the integer value range of unit8 or unit16 is [0,255] and [0,65535] respectively. The pixel value of the double class is a floating point number. The double-precision normalized brightness value range [0,1]
binary image
has only the values of 0 and 1.

b=logical(c);#c图像二值化。
 islogical(b);#判断b是否是逻辑数组
 b=data_class_name(a);#如 b=double(a);
 g=im2unit8(b);#小于0的转为0，大于1的转为255，之间数字乘以255，并四舍五入为最近的整数。
 d=g.';#d是g的转制
 d(1:3);#取d中前三个元素
 V(1:2:end)#步长为2取值
  V(end:-2:1)#步长为-2取值倒序
  fp=f(end:-1:1,:)#垂直翻转
  fc=f(257:768,257:768)#取图像的一部分
  fs=f(1：2：end,1:2:end);#二次采样
  k=size(A,1)#A的行数
  k=size(A,2)#A的列数

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zero(M,N);double类型的0
ones(M,N);
ture(M,N);
false(M,N);逻辑类型
magic(M,N);
rand(M,N);[0,1]间
randn(M,N);正态分布u（0，1）

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2.3 Matlab code optimization
1. Vectorized loop
0 for and while are converted into equivalent vector or matrix operations

for x=1:M
    f(x)=A*sin((x-1)/(2*pi));
end
优化后
x=1:M-1;
f=A*sin(x/(2*pi));

preallocated array

#加快执行时间另一种方法是在程序中**预分配数组的大小**,减少存储器碎片
f=zeros(1024);
g=zeros(1024);

2.4 Interactive I/O
0显示a矩阵disp（a）

t=input('enter your data:','s');#输入1 2 3时t=1 2 3，是char类型的class（t）

n=str2num(t)#转为数字类型
d=char(n)#转为char类型

Digital Image Processing - MATLAB-0

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