学步园

bmp文件，总的说来，可以分为以下4个部分

1. 文件头-----FILE_HEADER （总共14个字节）

2. 信息头-----INFO_HEADER  （总共40个字节）

3. 调色板----PALLET （单通道灰度图像才有，真彩色3通道图像没有）

4. 图像数据---IMAGE_DATA （实际图象像素数据）

bmp位图文件读写和显示到指定控件api简单封装，下面给出了封装源码的链接地址，欢迎大家一起交流，共同进步。

下载链接：http://download.csdn.net/detail/cimage/6610213

分别基本结构定义如下：

1. 文件头

struct tagBmpFileHeader //文件头
{
	unsigned short bfType;		//标识该文件为bmp文件,判断文件是否为bmp文件，即用该值与"0x4d42"比较是否相等即可，0x4d42 = 19778
	unsigned long  bfSize;		//文件大小
	unsigned short bfReserved1;	//预保留位
	unsigned short bfReserved2;	//预保留位
	unsigned long  bfOffBits;	//图像数据区的起始位置
}BmpFileHeader;//14字节

2. 信息头

struct tagBmpInfoHeader //信息头
{
	unsigned long  biSize;	//图像数据大小
	long     biWidth;	//宽度
	long     biHeight;	//高度
	unsigned short biPlanes;//为1
	unsigned short biBitCount; //像素位数，8-灰度图；24-真彩色
	unsigned longbiCompression;//压缩方式
	unsigned longbiSizeImage;  //图像区数据大小
	long     biXPelsPerMeter;  //水平分辨率，像素每米
	long     biYPelsPerMeter;
	unsigned long biClrUsed;   //位图实际用到的颜色数
	unsigned short biClrImportant;//位图显示过程，重要的颜色数；0--所有都重要
}BmpInfoHeader;//40字节

3. 调色板

struct tagRGBPallete //调色板
{
	unsigned char b;
	unsigned char g;
	unsigned char r;
	unsigned char alpha; //预保留位
}RGBPallete;

4. 定义一个图像结构

typedef struct tagVImage
{
	int width;
	int height;
	int channels;
	unsigned char* data;
}VImage;

5. bmp图像读取

VImage* LoadBMP(const char* filename)
{
	VImage* tempImage = (VImage*)malloc(sizeof(VImage));

	ULONGLONG position = 0;//文件中内容地址

	int szBmpFileHeader = 0, szBmpInfoHeader = 0, szRGBPallete = 0, szTemp = 0; 

	int width = 0, height = 0, nChannels = 0, widthStep = 0, index = 0;

	unsigned char* dataBuff = NULL;

	CFile bmpFile;

	if (!bmpFile.Open(filename, CFile::modeRead | CFile::shareDenyWrite))
		return NULL;

	szBmpFileHeader = sizeof(BmpFileHeader);
	szBmpInfoHeader = sizeof(BmpInfoHeader);
	szRGBPallete    = sizeof(RGBPallete);

	BmpFileHeader* pFileHeader = (BmpFileHeader*)malloc(szBmpFileHeader);

	szTemp = bmpFile.Read(pFileHeader, szBmpFileHeader); //文件头读取完毕

	position = bmpFile.Seek(szBmpFileHeader, CFile::begin); //跳转到文件头后地址处

	if (szTemp != szBmpFileHeader)
		return NULL;

	if (pFileHeader->bfType != 0x4d42)// 0x4d42 = 19778
		return NULL;

	BmpInfoHeader* pInfoHeader = (BmpInfoHeader*) malloc(szBmpInfoHeader);

	bmpFile.Read(pInfoHeader, szBmpInfoHeader); //信息头读取完毕

	position = bmpFile.Seek(szBmpInfoHeader + position, CFile::begin);//跳转到信息头后

	width = pInfoHeader->biWidth;
	height = pInfoHeader->biHeight;

	width = ((width + 3) >> 2) << 2;

	if (8 == pInfoHeader->biBitCount)//灰度图
	{
		RGBPallete* pRGBPallete = (RGBPallete*) malloc(256 * szRGBPallete);

		bmpFile.Read(pRGBPallete, 256 * szRGBPallete);//灰度图，读取调色板完毕

		position = bmpFile.Seek(256 * szRGBPallete + position, CFile::begin);

		nChannels = 1;
		widthStep = width;

		tempImage->width = width;
		tempImage->height = height;
		tempImage->channels = nChannels;

		tempImage->data = (unsigned char*) malloc(width * height);

		dataBuff = (unsigned char*) malloc(width * height);
		memset(dataBuff, 0, width * height);

		//bmpFile.Read(tempImage->data, width * height);//图像实际数据读取完毕
		bmpFile.Read(dataBuff, width * height);//图像实际数据读取完毕

		for (index = 0; index < height; index++)//bmp数据分布格式
		{
			memcpy(tempImage->data + index * width, dataBuff + (height - 1 - index) * width, width);
		}

		free(pFileHeader);
		free(pInfoHeader);
		free(pRGBPallete);
		free(dataBuff);

		pFileHeader = NULL;
		pInfoHeader = NULL;
		pRGBPallete = NULL;
		dataBuff = NULL;

		bmpFile.Close();//关闭文件

		return tempImage;
	}
	else if (24 == pInfoHeader->biBitCount) // 真彩色
	{
		nChannels = 3;
		widthStep = width * 3;

		tempImage->width = width;
		tempImage->height = height;
		tempImage->channels = nChannels;

		tempImage->data = (unsigned char*) malloc(widthStep * height);
		dataBuff = (unsigned char*) malloc(widthStep * height);

		//bmpFile.Read(tempImage->data, widthStep * height);
		bmpFile.Read(dataBuff, widthStep * height);

		for (index = 0; index < height; index++)//bmp数据分布格式为左下角到右上角，因此转换一下。
		{
			memcpy(tempImage->data + index * widthStep, dataBuff + (height - 1 - index) * widthStep, widthStep);
		}

		free(pFileHeader);
		free(pInfoHeader);
		free(dataBuff);

		dataBuff = NULL;
		pFileHeader = NULL;
		pInfoHeader = NULL;

		bmpFile.Close();

		return tempImage;
	}
	return NULL;
}