图像二值化、腐蚀、操作、闭操作与开操作

图像的二值化主要用到最大方差算法（又叫大津算法，otsu算法）

腐蚀(erosion)与膨胀(dilation)可以查阅相关资料。

开操作就是先对图像进行腐蚀，然后再膨胀。闭操作恰好相反。

以下代码只适用于24位bmp图像：

#include <cstdio>
#include <iostream>
#include <vector>
#include <algorithm>
#include <cstdlib>
#include <string>
using namespace std;
typedef unsigned char BYTE;
typedef unsigned short WORD;
typedef unsigned int DWORD;

//位图文件头定义;
typedef struct  tagBITMAPFILEHEADER{
//	WORD bfType;//单独读取，结构体中就不定义了
DWORD bfSize;//文件大小
WORD bfReserved1;//保留字
WORD bfReserved2;//保留字
DWORD bfOffBits;//从文件头到实际位图数据的偏移字节数
}BITMAPFILEHEADER;

typedef struct tagBITMAPINFOHEADER{
DWORD biSize;//信息头大小
DWORD biWidth;//图像宽度
DWORD biHeight;//图像高度
WORD biPlanes;//位平面数，必须为1
WORD biBitCount;//每像素位数
DWORD  biCompression; //压缩类型
DWORD  biSizeImage; //压缩图像大小字节数
DWORD  biXPelsPerMeter; //水平分辨率
DWORD  biYPelsPerMeter; //垂直分辨率
DWORD  biClrUsed; //位图实际用到的色彩数
DWORD  biClrImportant; //本位图中重要的色彩数
}BITMAPINFOHEADER; //位图信息头定义

//像素信息
typedef struct tagIMAGEDATA
{
BYTE blue;
BYTE green;
BYTE red;
}DATA;

BITMAPFILEHEADER strHead;
BITMAPINFOHEADER strInfo;
WORD bfType;
int h,w,size;
vector<vector<BYTE> > binarization;

void otsu(vector<vector<BYTE> >& src);
void printImage(vector<vector<BYTE> > src, string filename);
vector<vector<BYTE> > erosion(vector<vector<BYTE> > src);
vector<vector<BYTE> > dilation(vector<vector<BYTE> > src);

int main(){
FILE *fpi;
fpi=fopen("input.bmp","rb");
if(fpi != NULL){
//先读取文件类型
fread(&bfType,1,sizeof(WORD),fpi);
if(0x4d42!=bfType) {
cout<<"Error: The file is not a bmp image!"<<endl;
return 0;
}
//读取bmp文件的文件头和信息头
fread(&strHead,1,sizeof(tagBITMAPFILEHEADER),fpi);
fread(&strInfo,1,sizeof(tagBITMAPINFOHEADER),fpi);
h=strInfo.biHeight;
w=strInfo.biWidth;
if(h%4!=0)
h=(h/4+1)*4;
if(h*w*3!=strInfo.biSizeImage){
cout<<"Error: please choose a image whose horizontal pixels can be divided by 4！"<<endl;
return 0;
}
size=strInfo.biSizeImage/3;
binarization.clear();
binarization.resize(h);
for(int i = 0; i < h; i++)
binarization[i].resize(w);
//read the data area
DATA *imgdata=new DATA[size];
fread(imgdata,1,sizeof(DATA)*size,fpi);//读取bmp数据信息
fclose(fpi);

// cout<<"horizantal: "<< strInfo.biWidth<<endl;
// cout<<"vertical: "<< strInfo.biHeight<<endl;
// cout<<"multiple: "<< strInfo.biWidth * strInfo.biHeight * 3<<endl;
// cout<<"size: "<< strInfo.biSizeImage <<endl;

for(int i=0; i<size; i++){
BYTE gray = (imgdata[i].blue*11 + imgdata[i].red*30 + imgdata[i].green*59)/100;
binarization[i/w][i%w]=gray;
}

otsu(binarization);
printImage(binarization,"binarization.bmp");

vector<vector<BYTE> > erosionData = erosion(binarization);
printImage(erosionData,"erosion.bmp");

vector<vector<BYTE> > dilationData = dilation(binarization);
printImage(dilationData,"dilation.bmp");

vector<vector<BYTE> > openingData = dilation(erosionData);
printImage(openingData,"opening.bmp");

vector<vector<BYTE> > closingData = erosion(dilationData);
printImage(closingData,"closing.bmp");

}
else
{
cout<<"Can't open the file!"<<endl;
return 0;
}
return 0;
}

void printImage(vector<vector<BYTE> > src, string filename){
DATA* output = new DATA[size];
for(int i=0; i<size; i++){
BYTE tempByte = src[i/w][i%w];
output[i].blue = tempByte;
output[i].green = tempByte;
output[i].red = tempByte;
}
FILE *fpo1;
fpo1=fopen(filename.c_str(),"wb");
if(fpo1==NULL)
cout<<"wrong"<<endl;
fwrite(&bfType,1,sizeof(WORD),fpo1);
fwrite(&strHead,1,sizeof(tagBITMAPFILEHEADER),fpo1);
fwrite(&strInfo,1,sizeof(tagBITMAPINFOHEADER),fpo1);
fwrite(output,1,sizeof(DATA)*(size),fpo1);
fclose(fpo1);
delete[] output;
}

void otsu(vector<vector<BYTE> >& srcData){
int slideWindow = 4;	//let the sildewindow be 1/16 image size
int winH=h/slideWindow, winW=w/slideWindow;
int modified=70;
float histogram[256];
float avgValue=0;
int threshold;
for(int n = 0; n < slideWindow; n++){
for(int m = 0; m < slideWindow; m++){

memset(histogram,0,sizeof(histogram));
for(int i = n*winH; i<std::min(n*winH+winH,h); i++){
for(int j = m*winW; j<std::min(m*winW+winW,w); j++){
histogram[srcData[i][j]]++;
}
}
avgValue=0;
for(int i = 0; i < 256; i++){
histogram[i] = histogram[i] / size;
avgValue += i * histogram[i];
}
threshold=0;
float maxVariance=0;
float ww = 0, u = 0;
for(int i = 0; i < 256; i++)
{
ww += histogram[i];
u += i * histogram[i];

float t = avgValue * ww - u;
float variance = t * t / (ww * (1 - ww) );
if(variance > maxVariance)
{
maxVariance = variance;
threshold = i;
}
}
threshold-=modified;
for(int i = n*winH; i<std::min((int)(n*winH+winH),(int)h); i++){
for(int j = m*winW; j<std::min((int)(m*winW+winW),(int)w); j++){
// cout<<(int)srcData[i][j]<<" ";
if(srcData[i][j]>=threshold){
// cout<<"!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!"<<endl;
srcData[i][j]=255;
}
else
srcData[i][j]=0;
}
}
}
}
}

vector<vector<BYTE> > erosion(vector<vector<BYTE> > src){
vector<vector<BYTE> > modified(h+2);
for(int i = 0; i < modified.size(); i++)
modified[i].resize(w+2);
for(int i = 0; i < modified.size();i++){
if(i==0||i==modified.size()-1){
for(int j = 0; j < modified[i].size(); j++)
modified[i][j]=255;
}
else{
for(int j = 0; j < modified[i].size();j++){
if(j==0||j==modified[i].size()-1)
modified[i][j]=255;
else
modified[i][j]=src[i-1][j-1];
}
}
}

vector<vector<BYTE> > result(h);
for(int i = 0; i < result.size(); i++)
result[i].resize(w);
for(int i = 0; i < h; i++){
for(int j = 0; j < w; j++){
int sum = modified[i][j]+modified[i][j+1]+modified[i][j+2]
+modified[i+1][j]+modified[i+1][j+1]+modified[i+1][j+2]
+modified[i+2][j]+modified[i+2][j+1]+modified[i+2][j+2];
if(sum>0)
result[i][j]=255;
else
result[i][j]=0;
}
}
return result;
}

vector<vector<BYTE> > dilation(vector<vector<BYTE> > src){
vector<vector<BYTE> > modified(h+2);
for(int i = 0; i < modified.size(); i++)
modified[i].resize(w+2);
for(int i = 0; i < modified.size();i++){
if(i==0||i==modified.size()-1){
for(int j = 0; j < modified[i].size(); j++)
modified[i][j]=255;
}
else{
for(int j = 0; j < modified[i].size();j++){
if(j==0||j==modified[i].size()-1)
modified[i][j]=255;
else
modified[i][j]=src[i-1][j-1];
}
}
}

vector<vector<BYTE> > result(h);
for(int i = 0; i < result.size(); i++)
result[i].resize(w);
for(int i = 0; i < h; i++){
for(int j = 0; j < w; j++){
int sum = modified[i][j]+modified[i][j+1]+modified[i][j+2]
+modified[i+1][j]+modified[i+1][j+1]+modified[i+1][j+2]
+modified[i+2][j]+modified[i+2][j+1]+modified[i+2][j+2];
if(sum/9==255)
result[i][j]=255;
else
result[i][j]=0;
}
}
return result;
}