计算机视觉
图像处理

用C语言进行BMP文件的读写

BMP是BitMap(位图)的简称,也是所有windows上图片显示的基础。所有的图片格式,都必须转换成bmp才能进行最终的显示。所以,bmp文件的读写,就变得非常重要了。然而,很多人是借助于MFC类,C# 库函数,OpenCV,OpenGL等库函数进行bmp文件的读写。试想一下,如果你要在诸如DSP、FPGA之类的嵌入式设备上进行bmp文件的读写,总不能去安装一个庞大的MFC,C#类库吧?其实,我们完全可以抛开这些庞杂繁琐的类库和API函数,仅仅利用C语言,编写几个函数,就完全可以实现bmp文件的读写了。本文的意图正在于此。

一个完整的bmp位图文件,可以分为文件信息头,位图信息头和RGB颜色阵列三个部分(希望对这三部分有详细了解的可以参考我的另外一篇文章:http://blog.csdn.net/carson2005/article/details/6227047)。文件信息头主要包含“是否是BMP文件”,文件的大小等信息。而位图信息头则主要包含bmp文件的位图宽度,高度,位平面,通道数等信息。而RGB颜色阵列,里面才真正包含我们所需要的bmp位图的像素数据。需要提醒的是,bmp位图的颜色阵列部分,像素数据的存储是以左下角为原点。也就是说,当你打开一个bmp图片并显示在电脑屏幕上的时,实际在存储的时候,这个图片的最左下角的像素是首先被存储在bmp文件中的。之后,按照从左到右,从下到上的顺序,依次进行像素数据的存储。如果,你存储的是3通道的位图数据(也就是我们通常说的彩图),那么它是按照B0G0R0B1G1R1B2G2R2…的顺序进行存储的,同时,还要考虑到4字节对齐的问题。OK,了解了这些基本概念,相信,自己编程实现一些bmp文件的读写函数并非难事。这里,我给出C语言的版本,仅供参考,如有错误,欢迎指正。

chenLeeCV.h
#ifndef CHENLEECV_H
#define CHENLEECV_H

typedef struct
{
	//unsigned short    bfType;
	unsigned long    bfSize;
	unsigned short    bfReserved1;
	unsigned short    bfReserved2;
	unsigned long    bfOffBits;
} ClBitMapFileHeader;

typedef struct
{
	unsigned long  biSize; 
	long   biWidth; 
	long   biHeight; 
	unsigned short   biPlanes; 
	unsigned short   biBitCount;
	unsigned long  biCompression; 
	unsigned long  biSizeImage; 
	long   biXPelsPerMeter; 
	long   biYPelsPerMeter; 
	unsigned long   biClrUsed; 
	unsigned long   biClrImportant; 
} ClBitMapInfoHeader;

typedef struct 
{
	unsigned char rgbBlue; //该颜色的蓝色分量
	unsigned char rgbGreen; //该颜色的绿色分量
	unsigned char rgbRed; //该颜色的红色分量
	unsigned char rgbReserved; //保留值
} ClRgbQuad;

typedef struct
{
	int width;
	int height;
	int channels;
	unsigned char* imageData;
}ClImage;

ClImage* clLoadImage(char* path);
bool clSaveImage(char* path, ClImage* bmpImg);

#endif
	
chenLeeCV.cpp
#include "chenLeeCV.h"
#include 
#include 

ClImage* clLoadImage(char* path)
{
	ClImage* bmpImg;
	FILE* pFile;
	unsigned short fileType;
	ClBitMapFileHeader bmpFileHeader;
	ClBitMapInfoHeader bmpInfoHeader;
	int channels = 1;
	int width = 0;
	int height = 0;
	int step = 0;
	int offset = 0;
	unsigned char pixVal;
	ClRgbQuad* quad;
	int i, j, k;

	bmpImg = (ClImage*)malloc(sizeof(ClImage));
	pFile = fopen(path, "rb");
	if (!pFile)
	{
		free(bmpImg);
		return NULL;
	}

	fread(&fileType, sizeof(unsigned short), 1, pFile);
	if (fileType == 0x4D42)
	{
		//printf("bmp file! \n");

		fread(&bmpFileHeader, sizeof(ClBitMapFileHeader), 1, pFile);
		/*printf("\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\n");
		printf("bmp文件头信息:\n");
		printf("文件大小:%d \n", bmpFileHeader.bfSize);
		printf("保留字:%d \n", bmpFileHeader.bfReserved1);
		printf("保留字:%d \n", bmpFileHeader.bfReserved2);
		printf("位图数据偏移字节数:%d \n", bmpFileHeader.bfOffBits);*/

		fread(&bmpInfoHeader, sizeof(ClBitMapInfoHeader), 1, pFile);
		/*printf("\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\n");
		printf("bmp文件信息头\n");
		printf("结构体长度:%d \n", bmpInfoHeader.biSize);
		printf("位图宽度:%d \n", bmpInfoHeader.biWidth);
		printf("位图高度:%d \n", bmpInfoHeader.biHeight);
		printf("位图平面数:%d \n", bmpInfoHeader.biPlanes);
		printf("颜色位数:%d \n", bmpInfoHeader.biBitCount);
		printf("压缩方式:%d \n", bmpInfoHeader.biCompression);
		printf("实际位图数据占用的字节数:%d \n", bmpInfoHeader.biSizeImage);
		printf("X方向分辨率:%d \n", bmpInfoHeader.biXPelsPerMeter);
		printf("Y方向分辨率:%d \n", bmpInfoHeader.biYPelsPerMeter);
		printf("使用的颜色数:%d \n", bmpInfoHeader.biClrUsed);
		printf("重要颜色数:%d \n", bmpInfoHeader.biClrImportant);
		printf("\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\n");*/

		if (bmpInfoHeader.biBitCount == 8)
		{
			//printf("该文件有调色板,即该位图为非真彩色\n\n");
			channels = 1;
			width = bmpInfoHeader.biWidth;
			height = bmpInfoHeader.biHeight;
			offset = (channels*width)%4;
			if (offset != 0)
			{
				offset = 4 - offset;
			}
			//bmpImg->mat = kzCreateMat(height, width, 1, 0);
			bmpImg->width = width;
			bmpImg->height = height;
			bmpImg->channels = 1;
			bmpImg->imageData = (unsigned char*)malloc(sizeof(unsigned char)*width*height);
			step = channels*width;

			quad = (ClRgbQuad*)malloc(sizeof(ClRgbQuad)*256);
			fread(quad, sizeof(ClRgbQuad), 256, pFile);
			free(quad);

			for (i=0; i<height; i++)
			{
				for (j=0; j<width; j++) { fread(&pixVal, sizeof(unsigned char), 1, pFile); bmpImg->imageData[(height-1-i)*step+j] = pixVal;
				}
				if (offset != 0)
				{
					for (j=0; j<offset; j++) { fread(&pixVal, sizeof(unsigned char), 1, pFile); } } } } else if (bmpInfoHeader.biBitCount == 24) { //printf("该位图为位真彩色\n\n"); channels = 3; width = bmpInfoHeader.biWidth; height = bmpInfoHeader.biHeight; bmpImg->width = width;
			bmpImg->height = height;
			bmpImg->channels = 3;
			bmpImg->imageData = (unsigned char*)malloc(sizeof(unsigned char)*width*3*height);
			step = channels*width;

			offset = (channels*width)%4;
			if (offset != 0)
			{
				offset = 4 - offset;
			}

			for (i=0; i<height; i++)
			{
				for (j=0; j<width; j++)
				{
					for (k=0; k<3; k++) { fread(&pixVal, sizeof(unsigned char), 1, pFile); bmpImg->imageData[(height-1-i)*step+j*3+k] = pixVal;
					}
					//kzSetMat(bmpImg->mat, height-1-i, j, kzScalar(pixVal[0], pixVal[1], pixVal[2]));
				}
				if (offset != 0)
				{
					for (j=0; j<offset; j++) { fread(&pixVal, sizeof(unsigned char), 1, pFile); } } } } } return bmpImg; } bool clSaveImage(char* path, ClImage* bmpImg) { FILE *pFile; unsigned short fileType; ClBitMapFileHeader bmpFileHeader; ClBitMapInfoHeader bmpInfoHeader; int step; int offset; unsigned char pixVal = '\0'; int i, j; ClRgbQuad* quad; pFile = fopen(path, "wb"); if (!pFile) { return false; } fileType = 0x4D42; fwrite(&fileType, sizeof(unsigned short), 1, pFile); if (bmpImg->channels == 3)//24位,通道,彩图
	{
		step = bmpImg->channels*bmpImg->width;
		offset = step%4;
		if (offset != 4)
		{
			step += 4-offset;
		}

		bmpFileHeader.bfSize = bmpImg->height*step + 54;
		bmpFileHeader.bfReserved1 = 0;
		bmpFileHeader.bfReserved2 = 0;
		bmpFileHeader.bfOffBits = 54;
		fwrite(&bmpFileHeader, sizeof(ClBitMapFileHeader), 1, pFile);

		bmpInfoHeader.biSize = 40;
		bmpInfoHeader.biWidth = bmpImg->width;
		bmpInfoHeader.biHeight = bmpImg->height;
		bmpInfoHeader.biPlanes = 1;
		bmpInfoHeader.biBitCount = 24;
		bmpInfoHeader.biCompression = 0;
		bmpInfoHeader.biSizeImage = bmpImg->height*step;
		bmpInfoHeader.biXPelsPerMeter = 0;
		bmpInfoHeader.biYPelsPerMeter = 0;
		bmpInfoHeader.biClrUsed = 0;
		bmpInfoHeader.biClrImportant = 0;
		fwrite(&bmpInfoHeader, sizeof(ClBitMapInfoHeader), 1, pFile);

		for (i=bmpImg->height-1; i>-1; i--)
		{
			for (j=0; jwidth; j++)
			{
				pixVal = bmpImg->imageData[i*bmpImg->width*3+j*3];
				fwrite(&pixVal, sizeof(unsigned char), 1, pFile);
				pixVal = bmpImg->imageData[i*bmpImg->width*3+j*3+1];
				fwrite(&pixVal, sizeof(unsigned char), 1, pFile);
				pixVal = bmpImg->imageData[i*bmpImg->width*3+j*3+2];
				fwrite(&pixVal, sizeof(unsigned char), 1, pFile);
			}
			if (offset!=0)
			{
				for (j=0; j<offset; j++) { pixVal = 0; fwrite(&pixVal, sizeof(unsigned char), 1, pFile); } } } } else if (bmpImg->channels == 1)//8位,单通道,灰度图
	{
		step = bmpImg->width;
		offset = step%4;
		if (offset != 4)
		{
			step += 4-offset;
		}

		bmpFileHeader.bfSize = 54 + 256*4 + bmpImg->width;
		bmpFileHeader.bfReserved1 = 0;
		bmpFileHeader.bfReserved2 = 0;
		bmpFileHeader.bfOffBits = 54 + 256*4;
		fwrite(&bmpFileHeader, sizeof(ClBitMapFileHeader), 1, pFile);

		bmpInfoHeader.biSize = 40;
		bmpInfoHeader.biWidth = bmpImg->width;
		bmpInfoHeader.biHeight = bmpImg->height;
		bmpInfoHeader.biPlanes = 1;
		bmpInfoHeader.biBitCount = 8;
		bmpInfoHeader.biCompression = 0;
		bmpInfoHeader.biSizeImage = bmpImg->height*step;
		bmpInfoHeader.biXPelsPerMeter = 0;
		bmpInfoHeader.biYPelsPerMeter = 0;
		bmpInfoHeader.biClrUsed = 256;
		bmpInfoHeader.biClrImportant = 256;
		fwrite(&bmpInfoHeader, sizeof(ClBitMapInfoHeader), 1, pFile);

		quad = (ClRgbQuad*)malloc(sizeof(ClRgbQuad)*256);
		for (i=0; i<256; i++) { quad[i].rgbBlue = i; quad[i].rgbGreen = i; quad[i].rgbRed = i; quad[i].rgbReserved = 0; } fwrite(quad, sizeof(ClRgbQuad), 256, pFile); free(quad); for (i=bmpImg->height-1; i>-1; i--)
		{
			for (j=0; jwidth; j++)
			{
				pixVal = bmpImg->imageData[i*bmpImg->width+j];
				fwrite(&pixVal, sizeof(unsigned char), 1, pFile);
			}
			if (offset!=0)
			{
				for (j=0; j<offset; j++)
				{
					pixVal = 0;
					fwrite(&pixVal, sizeof(unsigned char), 1, pFile);
				}
			}
		}
	}
	fclose(pFile);

	return true;
}

Main.cpp
#include "stdafx.h"
#include "chenLeeCV.h"


int _tmain(int argc, _TCHAR* argv[])
{
	ClImage* img = clLoadImage("c:/test.bmp");
	bool flag = clSaveImage("c:/result.bmp", img);
	if(flag)
	{
		printf("save ok... \n");
	}
	

	while(1);
	return 0;
}

转载注明来源:CV视觉网 » 用C语言进行BMP文件的读写

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