Bitmap文件格式+生成一个BMP文件

Bitmap的文件格式：

#define UINT16    unsigned short
#define DWORD    unsigned int
#define WORD    short
#define LONG    int

// Bitmap File Header ( 14 Bytes )
typedef struct tagBITMAPFILEHEADER 
{  
    UINT16 bfType;        // same as BM in ASCII.
    DWORD bfSize;         // the size of the BMP file in bytes
    UINT16 bfReserved1; 
    UINT16 bfReserved2; 
    DWORD bfOffBits;    // starting address, of the byte where the bitmap image data (Pixel Array) can be found.
} BITMAPFILEHEADER, *PBITMAPFILEHEADER;

// DIB头描述bitmap的信息，包括大小、压缩类型、颜色格式等，DIB头的大小根据版本不同，大小也不同。
typedef struct tagBITMAPINFOHEADER
{
    DWORD biSize;             // 4, the size of this header (40 bytes)
    LONG biWidth;             // 4, the bitmap width in pixels (signed integer).
    LONG biHeight;             // 4, the bitmap height in pixels (signed integer).
    WORD biPlanes;             // 2, the number of color planes being used. Must be set to 1.
    WORD biBitCount;         // 2, the number of bits per pixel, which is the color depth of the image. Typical values are 1, 4, 8, 16, 24 and 32.
    DWORD biCompression;     // 4, the compression method being used. 
    DWORD biSizeImage;         // 4, the image size. This is the size of the raw bitmap data, and should not be confused with the file size.
    LONG biXPelsPerMeter;     // 4, the horizontal resolution of the image.
    LONG biYPelsPerMeter;     // 4, the vertical resolution of the image. 
    DWORD biClrUsed;         // 4, the number of colors in the color palette, or 0 to default to 2^n.
    DWORD biClrImportant;    // 4, the number of important colors used, or 0 when every color is important; generally ignored.
} BITMAPINFOHEADER;

生成一个BMP文件：

int bitmap_file_generate( char *name, int width, int height )
{
    FILE *fp = NULL;
    unsigned char *pData;
    unsigned char *pp;
    int i, j;
    int iFileSize;
    
    unsigned char bfType1, bfType2;
    unsigned int bfSize;
    unsigned short bfReserved1, bfReserved2;
    unsigned int bfOffBits;
    unsigned int biSize;
    int biWidth, biHeight;
    unsigned short biPlanes;
    unsigned short biBitCount;
    unsigned int biCompression;
    unsigned int biSizeImage;
    unsigned int biXPelsPerMeter;
    unsigned int biYPelsPerMeter;
    unsigned int biClrUsed;
    unsigned int biClrImportant;
    
    // offset[0:1]
    bfType1   = 'B';
    bfType2   = 'M';
    // offset[2:5]
    bfSize    = width * height * 3 + 54;
    // offset[6:7]
    bfReserved1 = 0;
    // offsset[8:9]
    bfReserved2 = 0;
    // offset[10:13]
    bfOffBits = 54;
    // offset[14:17]
    biSize = 40;
    // offset[18:21]
    biWidth = width;
    // offset[22:25]
    biHeight = height;
    // offset[26:27]
    biPlanes = 1;
    // offset[28:29]
    biBitCount = 24;
    // offset[30:33]
    biCompression = 0;
    // offset[34:37]
    biSizeImage = width * height * 3;
    // offset[38:41]
    biXPelsPerMeter = 2835;
    // offset[42:45]
    biYPelsPerMeter = 2835;
    // offset[46:49]
    biClrUsed = 0;
    // offset[50:53]
    biClrImportant = 0;
    
    
    fp = fopen(name, "wb+");
    if( fp == NULL )
    {
        printf("create file err, fopen: %p
", fp);
        return -1;    
    }
    
    pData = (unsigned char *)malloc(biWidth*biHeight*3+54);//malloc(iFileSize);
    if(pData == NULL)
    {
        printf("pData malloc err
");
        return -2;
    }
    
    // same as BM in ASCII.
    pData[0] = bfType1;
    pData[1] = bfType2;
    
    // the size of the BMP file in bytes. bmp文件的实际大小
    pData[2] = (unsigned char)((bfSize>>0) & 0xff);
    pData[3] = (unsigned char)((bfSize>>8) & 0xff);
    pData[4] = (unsigned char)((bfSize>>16) & 0xff);    
    pData[5] = (unsigned char)((bfSize>>24) & 0xff);
    
    // reserved
    pData[6] = (unsigned char)((bfReserved1>>0) & 0xff);
    pData[7] = (unsigned char)((bfReserved1>>8) & 0xff);
    // reserved
    pData[8] = (unsigned char)((bfReserved2>>0) & 0xff);
    pData[9] = (unsigned char)((bfReserved2>>0) & 0xff);
    
    // the offset, i.e. starting address, of the byte where the bitmap image data (Pixel Array) can be found.
    // 颜色数据的偏移地址，实际为：54 = 14 + 40
    pData[10] = (unsigned char)((bfOffBits>>0) & 0xff);
    pData[11] = (unsigned char)((bfOffBits>>8) & 0xff);
    pData[12] = (unsigned char)((bfOffBits>>16) & 0xff);    
    pData[13] = (unsigned char)((bfOffBits>>24) & 0xff);
    
    // the size of this header (40 bytes)
    pData[14] = (unsigned char)((biSize>>0) & 0xff);
    pData[15] = (unsigned char)((biSize>>8) & 0xff);
    pData[16] = (unsigned char)((biSize>>16) & 0xff);    
    pData[17] = (unsigned char)((biSize>>24) & 0xff);
    
    // the bitmap width in pixels (signed integer).
    pData[18] = (unsigned char)((biWidth>>0) & 0xff);
    pData[19] = (unsigned char)((biWidth>>8) & 0xff);
    pData[20] = (unsigned char)((biWidth>>16) & 0xff);
    pData[21] = (unsigned char)((biWidth>>24) & 0xff);
    
    // the bitmap height in pixels (signed integer).
    pData[22] = (unsigned char)((biHeight>>0) & 0xff);
    pData[23] = (unsigned char)((biHeight>>8) & 0xff);
    pData[24] = (unsigned char)((biHeight>>16) & 0xff);
    pData[25] = (unsigned char)((biHeight>>24) & 0xff);
    
    // the number of color planes being used. Must be set to 1.
    pData[26] = (unsigned char)((biPlanes>>0) & 0xff);
    pData[27] = (unsigned char)((biPlanes>>8) & 0xff);
    
    // the number of bits per pixel, which is the color depth of the image. Typical values are 1, 4, 8, 16, 24 and 32.
    pData[28] = (unsigned char)((biBitCount>>0) & 0xff);
    pData[29] = (unsigned char)((biBitCount>>8) & 0xff);
    
    // the compression method being used. See the next table for a list of possible values.
    pData[30] = (unsigned char)((biCompression>>0) & 0xff);
    pData[31] = (unsigned char)((biCompression>>8) & 0xff);
    pData[32] = (unsigned char)((biCompression>>16) & 0xff);
    pData[33] = (unsigned char)((biCompression>>24) & 0xff);
    
    // the image size. This is the size of the raw bitmap data, and should not be confused with the file size.
    pData[34] = (unsigned char)((biSizeImage>>0) & 0xff);
    pData[35] = (unsigned char)((biSizeImage>>8) & 0xff);
    pData[36] = (unsigned char)((biSizeImage>>16) & 0xff);
    pData[37] = (unsigned char)((biSizeImage>>24) & 0xff);
    
    // the horizontal resolution of the image. (pixel per meter, signed integer)
    pData[38] = (unsigned char)((biXPelsPerMeter>>0) & 0xff);
    pData[39] = (unsigned char)((biXPelsPerMeter>>8) & 0xff);
    pData[40] = (unsigned char)((biXPelsPerMeter>>16) & 0xff);
    pData[41] = (unsigned char)((biXPelsPerMeter>>24) & 0xff);
    
    // the vertical resolution of the image. (pixel per meter, signed integer)
    pData[42] = (unsigned char)((biYPelsPerMeter>>0) & 0xff);
    pData[43] = (unsigned char)((biYPelsPerMeter>>8) & 0xff);
    pData[44] = (unsigned char)((biYPelsPerMeter>>16) & 0xff);
    pData[45] = (unsigned char)((biYPelsPerMeter>>24) & 0xff);  
    
     // the number of colors in the color palette, or 0 to default to 2^n.
    pData[46] = (unsigned char)((biClrUsed>>0) & 0xff);
    pData[47] = (unsigned char)((biClrUsed>>8) & 0xff);
    pData[48] = (unsigned char)((biClrUsed>>16) & 0xff);
    pData[49] = (unsigned char)((biClrUsed>>24) & 0xff);  
    
     // the number of important colors used, or 0 when every color is important; generally ignored.
    pData[50] = (unsigned char)((biClrImportant>>0) & 0xff);
    pData[51] = (unsigned char)((biClrImportant>>8) & 0xff);
    pData[52] = (unsigned char)((biClrImportant>>16) & 0xff);
    pData[53] = (unsigned char)((biClrImportant>>24) & 0xff);     


    pp = &pData[54];
    for(i = 0; i < biHeight; i++)
    {
        for(j = 0; j < biWidth; j++)
        {
            set_color(pp, biWidth, biHeight, i, j, i+j, i, j);  // 随便填有点颜色
        }
    } 
    
    iFileSize = fwrite(pData, 1, bfSize, fp);
    printf("generate file iFileSize: %d
", iFileSize);
    
    free(pData);
    
    fclose(fp);
    
    return 0;
}

以上生成的BMP，坐标起始位置(0,0)为左下角，填充颜色：

void set_color( unsigned char *pp, int w, int h, 
    int x, int y, unsigned char r, unsigned char g, unsigned char b )
{
    pp[y*w*3+x*3+0] = (unsigned char)r;
    pp[y*w*3+x*3+1] = (unsigned char)g;
    pp[y*w*3+x*3+2] = (unsigned char)b;
}

生成一个，~~~~(>_<)~~~~：

int main(int argc, char *argv[])
{
    int ret;
    char *file_name;
    
    if( argc != 2 )
    {
        printf("please input bitmap file_name
");
        printf("usage: %s bitmap_file_name
", argv[0]);
        return 0;
    }
    
    file_name = argv[1];
    
    ret = bitmap_file_generate(file_name, 1024*10, 1024*10);
    
    printf("bitmap_file_generate, ret: %d
", ret);

    return 0;    
}