C++—— 读入一张bmp图片，提取其图像数据，存入矩阵/txt文件

本文章完成的是读入bmp图片、将数据存入矩阵/TXT文件、保存图片的功能。

在开始之前，我们需要了解bmp位图的存储方式:

BMP文件的数据按照从文件头开始的先后顺序分为四个部分：
（1）bmp文件头(bmp file header)：提供文件的格式、大小等信息
（2）位图信息头(bitmap information)：提供图像数据的尺寸、位平面数、压缩方式、颜色索引等信息
（3）调色板(color palette)：可选，如使用索引来表示图像，调色板就是索引与其对应的颜色的映射表

（4）位图数据(bitmap data)：图像数据,像素按照从下到上、从左到右的顺序每行占用的空间必须是4的整数倍

read_save.h

#include<fstream>
#include<windows.h>
#include<iostream>
using namespace std;


unsigned char *pBmpBuf;//读入图像数据的指针
int bmpWidth;//图像的宽
int bmpHeight;//图像的高
RGBQUAD *pColorTable;//颜色表指针
int biBitCount;//图像类型，每像素位数



//显示位图文件头信息   
void showBmpHead(BITMAPFILEHEADER pBmpHead){
	cout << "\n位图文件头:" << endl;
	cout << "文件大小:" << pBmpHead.bfSize << endl; 
	cout << "保留字_1:" << pBmpHead.bfReserved1 << endl;
	cout << "保留字_2:" << pBmpHead.bfReserved2 << endl;
	cout << "实际位图数据的偏移字节数:" << pBmpHead.bfOffBits << endl << endl;
}
//显示位图信息头信息  
void showBmpInforHead(BITMAPINFOHEADER pBmpInforHead){
	cout << "\n位图信息头:" << endl;
	cout << "结构体的长度:" << pBmpInforHead.biSize << endl;
	cout << "位图宽:" << pBmpInforHead.biWidth << endl;
	cout << "位图高:" << pBmpInforHead.biHeight << endl;
	cout << "biPlanes平面数:" << pBmpInforHead.biPlanes << endl;
	cout << "biBitCount采用颜色位数:" << pBmpInforHead.biBitCount << endl;
	cout << "压缩方式:" << pBmpInforHead.biCompression << endl;
	cout << "biSizeImage实际位图数据占用的字节数:" << pBmpInforHead.biSizeImage << endl;
	cout << "X方向分辨率:" << pBmpInforHead.biXPelsPerMeter << endl;
	cout << "Y方向分辨率:" << pBmpInforHead.biYPelsPerMeter << endl;
	cout << "使用的颜色数:" << pBmpInforHead.biClrUsed << endl;
	cout << "重要颜色数:" << pBmpInforHead.biClrImportant << endl;
}
//-----------------------------------------------------------------------------------------
//给定一个图像位图数据、宽、高、颜色表指针及每像素所占的位数等信息,将其写到指定文件中
bool readBmp(char *bmpName)
{
	FILE *fp = fopen(bmpName, "rb");//二进制读方式打开指定的图像文件
	if (fp == 0)
		return 0;

	//跳过位图文件头结构BITMAPFILEHEADER
	fseek(fp, sizeof(BITMAPFILEHEADER), 0);
	/*
	BITMAPFILEHEADER filehead;
	fread(&filehead, 1, sizeof(BITMAPFILEHEADER), fp);
	showBmpHead(filehead);//显示文件头   
*/

	//定义位图信息头结构变量，读取位图信息头进内存，存放在变量head中
	BITMAPINFOHEADER infohead;
	fread(&infohead, sizeof(BITMAPINFOHEADER), 1, fp); //获取图像宽、高、每像素所占位数等信息
	bmpWidth = infohead.biWidth;
	bmpHeight = infohead.biHeight;
	biBitCount = infohead.biBitCount;//定义变量，计算图像每行像素所占的字节数（必须是4的倍数）
	showBmpInforHead(infohead);//显示信息头 


	int lineByte = (bmpWidth * biBitCount / 8 + 3) / 4 * 4;//灰度图像有颜色表，且颜色表表项为256
	if (biBitCount == 8)
	{
		//申请颜色表所需要的空间，读颜色表进内存
		pColorTable = new RGBQUAD[256];
		fread(pColorTable, sizeof(RGBQUAD), 256, fp);
	}

	//申请位图数据所需要的空间，读位图数据进内存
	pBmpBuf = new unsigned char[lineByte * bmpHeight];
	fread(pBmpBuf, 1, lineByte * bmpHeight, fp);
	fclose(fp);//关闭文件
	return 1;//读取文件成功
}



//保存图片
bool saveBmp(char *bmpName, unsigned char *imgBuf, int width, int height, int biBitCount, RGBQUAD *pColorTable)
{

	//如果位图数据指针为0，则没有数据传入，函数返回
	if (!imgBuf)
		return 0;
	//颜色表大小，以字节为单位，灰度图像颜色表为1024字节，彩色图像颜色表大小为0
	int colorTablesize = 0;
	if (biBitCount == 8)
		colorTablesize = 1024;

	//待存储图像数据每行字节数为4的倍数
	int lineByte = (width * biBitCount / 8 + 3) / 4 * 4;

	//以二进制写的方式打开文件
	FILE *fp = fopen(bmpName, "wb");

	if (fp == 0)
		return 0;
//------------------------------------------------------------------------------------------------------------------
	//申请位图文件头结构变量，填写文件头信息
	BITMAPFILEHEADER fileHead;
	fileHead.bfType = 0x4D42;//bmp类型

	//bfSize是图像文件4个组成部分之和
	fileHead.bfSize = sizeof(BITMAPFILEHEADER) + sizeof(BITMAPINFOHEADER) + colorTablesize + lineByte*height;
	fileHead.bfReserved1 = 0;
	fileHead.bfReserved2 = 0;

	//bfOffBits是图像文件前3个部分所需空间之和
	fileHead.bfOffBits = 54 + colorTablesize;
//--------------------------------------------------------------------------------------------------------------------
	//写文件头进文件
	fwrite(&fileHead, sizeof(BITMAPFILEHEADER), 1, fp);

	//申请位图信息头结构变量，填写信息头信息
	BITMAPINFOHEADER infohead;
	infohead.biBitCount = biBitCount;
	infohead.biClrImportant = 0;
	infohead.biClrUsed = 0;
	infohead.biCompression = 0;
	infohead.biHeight = height;
	infohead.biPlanes = 1;
	infohead.biSize = 40;
	infohead.biSizeImage = lineByte*height;
	infohead.biWidth = width;
	infohead.biXPelsPerMeter = 0;
	infohead.biYPelsPerMeter = 0;

	//写位图信息头进内存
	fwrite(&infohead, sizeof(BITMAPINFOHEADER), 1, fp);
//----------------------------------------------------------------------------------------------------------------------
	//如果灰度图像，有颜色表，写入文件 
	if (biBitCount == 8)
		fwrite(pColorTable, sizeof(RGBQUAD), 256, fp);

	//写位图数据进文件
	fwrite(imgBuf, height*lineByte, 1, fp);

	//关闭文件
	fclose(fp);
	return 1;

}

read.cpp

#include<cstdlib>
#include<cstdio>
#include<cmath>
#include<iomanip>

#include"readbmp.h"
#include"savebmp.h"

using namespace std;

//unsigned int out_r[2000][2000];
//unsigned int out_g[2000][2000];
//unsigned int out_b[2000][2000];
unsigned int **out_r;
unsigned int **out_g;
unsigned int **out_b;

void doIt()
{

	char readPath[] = "D:\\C++_file\\image_deal_C++\\read_BMP\\lunpan.bmp";
	readBmp(readPath);
	// 输出整体图像信息
	cout << "\nwidth=" << bmpWidth << "\nheight=" << bmpHeight << "\nbiBitCount=" << biBitCount << endl;
	// 图像的字节数
	int linebyte1 = (bmpWidth*biBitCount / 8 + 3) / 4 * 4;
	int n = 0, m = 0, count_xiang_su = 0;

	out_r = new unsigned int *[bmpHeight];        //开辟指针数组
	for (int i = 0; i<bmpHeight; i++)
		out_r[i] = new unsigned int[bmpWidth];

	out_g = new unsigned int *[bmpHeight];        //开辟指针数组
	for (int i = 0; i<bmpHeight; i++)
		out_g[i] = new unsigned int[bmpWidth];

	out_b = new unsigned int *[bmpHeight];        //开辟指针数组
	for (int i = 0; i<bmpHeight; i++)
		out_b[i] = new unsigned int[bmpWidth];


	//初始化原始像素的数组。

	if (biBitCount == 8)
	{
		for (int i = 0; i<bmpHeight / 2; i++)
		{
			for (int j = 0; j<bmpWidth / 2; i++)
				*(pBmpBuf + i*linebyte1 + j) = 0;
		}
	}

	if (biBitCount == 24)
	{
		for (int i = 0; i<bmpHeight; i++)
		{
			for (int j = 0; j<bmpWidth; j++)
			{
				for (int k = 0; k<3; k++)//每像素RGB三个分量分别置0才变成黑色
				{
					m = *(pBmpBuf + i*linebyte1 + j * 3 + k);
					count_xiang_su++;
				}
				n++;
			}
		}
		cout << "总的像素个素为:" << n << endl;
		cout << "----------------------------------------------------" << endl;
	}


	if (biBitCount == 24)
	{
		for (int i = 0; i<bmpHeight; i++)
		{
			for (int j = 0; j<bmpWidth; j++)
			{
				out_r[bmpHeight - 1 - i][j] = pBmpBuf[j * 3 + 2 + bmpWidth*i * 3];
				out_g[bmpHeight - 1 - i][j] = pBmpBuf[j * 3 + 1 + bmpWidth *i * 3];
				out_b[bmpHeight - 1 - i][j] = pBmpBuf[j * 3 + bmpWidth *i * 3];
			}
		}
		//	for (int i = 0; i<bmpHeight; i++)
		//	{
		//		for (int j = 0; j<bmpWidth; j++)
		//		{
		//			cout<<out_r[i][j]<<endl;
		//			cout << out_g[i][j] << endl;
		//			cout << out_b[i][j] << endl;
		//		}
		//	}
	}

	//---------------------------------------------------------------------------------------
	/*//将像素数据存入TXT文件。
	ofstream outfile;
	outfile.open("rrbmp.txt", ios::in | ios::trunc);
	if(!outfile) cout << "error" << endl;
	for (int i = 0; i<bmpHeight; i++)
	{
	for (int j = 0; j<bmpWidth; j++)
	{
	outfile << out_r[i][j] << " ";
	//cout << out_g[i][j] << endl;
	//cout << out_b[i][j] << endl;
	}
	outfile << "\n";
	}
	outfile.close();
	*/
	// jiang tuxiang shuju cunpan .
	char writePath[] = "D:\\C++_file\\image_deal_C++\\read_BMP\\1.bmp";
	saveBmp(writePath, pBmpBuf, bmpWidth, bmpHeight, biBitCount, pColorTable);

	//清除缓冲区，pBmpBuf和pColorTable是全局变量，在文件读入时申请的空间
	delete[]pBmpBuf;
	if (biBitCount == 8)
		delete[]pColorTable;

}

//
int main()
{

	doIt();
	system("pause");
	return 0;
}