用C语言进行BMP文件的读写

winston · 发表于 2011-12-17 20:20:30

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 <stdio.h>
#include <stdlib.h>
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1：%d \n", bmpFileHeader.bfReserved1);
printf("保留字2：%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24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，3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; j<bmpImg->width; 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; j<bmpImg->width; 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;
}

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作者：carson2005 发表于2011-12-17 17:10:22 原文链接

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