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 *  + ;
     // offset[6:7]
     bfReserved1 = ;
     // offsset[8:9]
     bfReserved2 = ;
     // offset[10:13]
     bfOffBits = ;
     // offset[14:17]
     biSize = ;
     // offset[18:21]
     biWidth = width;
     // offset[22:25]
     biHeight = height;
     // offset[26:27]
     biPlanes = ;
     // offset[28:29]
     biBitCount = ;
     // offset[30:33]
     biCompression = ;
     // offset[34:37]
     biSizeImage = width * height * ;
     // offset[38:41]
     biXPelsPerMeter = ;
     // offset[42:45]
     biYPelsPerMeter = ;
     // offset[46:49]
     biClrUsed = ;
     // offset[50:53]
     biClrImportant = ;

     fp = fopen(name, "wb+");
     if( fp == NULL )
     {
         printf("create file err, fopen: %p\n", fp);
         return -;
     }

     pData = (unsigned char *)malloc(biWidth*biHeight*+);//malloc(iFileSize);
     if(pData == NULL)
     {
         printf("pData malloc err\n");
         return -;
     }

     // same as BM in ASCII.
     pData[] = bfType1;
     pData[] = bfType2;

     // the size of the BMP file in bytes. bmp文件的实际大小
     pData[] = (unsigned char)((bfSize>>) & 0xff);
     pData[] = (unsigned char)((bfSize>>) & 0xff);
     pData[] = (unsigned char)((bfSize>>) & 0xff);
     pData[] = (unsigned char)((bfSize>>) & 0xff);

     // reserved
     pData[] = (unsigned char)((bfReserved1>>) & 0xff);
     pData[] = (unsigned char)((bfReserved1>>) & 0xff);
     // reserved
     pData[] = (unsigned char)((bfReserved2>>) & 0xff);
     pData[] = (unsigned char)((bfReserved2>>) & 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[] = (unsigned char)((bfOffBits>>) & 0xff);
     pData[] = (unsigned char)((bfOffBits>>) & 0xff);
     pData[] = (unsigned char)((bfOffBits>>) & 0xff);
     pData[] = (unsigned char)((bfOffBits>>) & 0xff);

     // the size of this header (40 bytes)
     pData[] = (unsigned char)((biSize>>) & 0xff);
     pData[] = (unsigned char)((biSize>>) & 0xff);
     pData[] = (unsigned char)((biSize>>) & 0xff);
     pData[] = (unsigned char)((biSize>>) & 0xff);

     // the bitmap width in pixels (signed integer).
     pData[] = (unsigned char)((biWidth>>) & 0xff);
     pData[] = (unsigned char)((biWidth>>) & 0xff);
     pData[] = (unsigned char)((biWidth>>) & 0xff);
     pData[] = (unsigned char)((biWidth>>) & 0xff);

     // the bitmap height in pixels (signed integer).
     pData[] = (unsigned char)((biHeight>>) & 0xff);
     pData[] = (unsigned char)((biHeight>>) & 0xff);
     pData[] = (unsigned char)((biHeight>>) & 0xff);
     pData[] = (unsigned char)((biHeight>>) & 0xff);

     // the number of color planes being used. Must be set to 1.
     pData[] = (unsigned char)((biPlanes>>) & 0xff);
     pData[] = (unsigned char)((biPlanes>>) & 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[] = (unsigned char)((biBitCount>>) & 0xff);
     pData[] = (unsigned char)((biBitCount>>) & 0xff);

     // the compression method being used. See the next table for a list of possible values.
     pData[] = (unsigned char)((biCompression>>) & 0xff);
     pData[] = (unsigned char)((biCompression>>) & 0xff);
     pData[] = (unsigned char)((biCompression>>) & 0xff);
     pData[] = (unsigned char)((biCompression>>) & 0xff);

     // the image size. This is the size of the raw bitmap data, and should not be confused with the file size.
     pData[] = (unsigned char)((biSizeImage>>) & 0xff);
     pData[] = (unsigned char)((biSizeImage>>) & 0xff);
     pData[] = (unsigned char)((biSizeImage>>) & 0xff);
     pData[] = (unsigned char)((biSizeImage>>) & 0xff);

     // the horizontal resolution of the image. (pixel per meter, signed integer)
     pData[] = (unsigned char)((biXPelsPerMeter>>) & 0xff);
     pData[] = (unsigned char)((biXPelsPerMeter>>) & 0xff);
     pData[] = (unsigned char)((biXPelsPerMeter>>) & 0xff);
     pData[] = (unsigned char)((biXPelsPerMeter>>) & 0xff);

     // the vertical resolution of the image. (pixel per meter, signed integer)
     pData[] = (unsigned char)((biYPelsPerMeter>>) & 0xff);
     pData[] = (unsigned char)((biYPelsPerMeter>>) & 0xff);
     pData[] = (unsigned char)((biYPelsPerMeter>>) & 0xff);
     pData[] = (unsigned char)((biYPelsPerMeter>>) & 0xff);  

      // the number of colors in the color palette, or 0 to default to 2^n.
     pData[] = (unsigned char)((biClrUsed>>) & 0xff);
     pData[] = (unsigned char)((biClrUsed>>) & 0xff);
     pData[] = (unsigned char)((biClrUsed>>) & 0xff);
     pData[] = (unsigned char)((biClrUsed>>) & 0xff);  

      // the number of important colors used, or 0 when every color is important; generally ignored.
     pData[] = (unsigned char)((biClrImportant>>) & 0xff);
     pData[] = (unsigned char)((biClrImportant>>) & 0xff);
     pData[] = (unsigned char)((biClrImportant>>) & 0xff);
     pData[] = (unsigned char)((biClrImportant>>) & 0xff);     

     pp = &pData[];
     for(i = ; i < biHeight; i++)
     {
         for(j = ; j < biWidth; j++)
         {
             set_color(pp, biWidth, biHeight, i, j, i+j, i, j);  // 随便填有点颜色
         }
     } 

     iFileSize = fwrite(pData, , bfSize, fp);
     printf("generate file iFileSize: %d\n", iFileSize);

     free(pData);

     fclose(fp);

     return ;
 }

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*+x*+] = (unsigned char)r;
     pp[y*w*+x*+] = (unsigned char)g;
     pp[y*w*+x*+] = (unsigned char)b;
 }

生成一个，~~~~(>_<)~~~~：

 int main(int argc, char *argv[])
 {
     int ret;
     char *file_name;

     if( argc !=  )
     {
         printf("please input bitmap file_name\n");
         printf("usage: %s bitmap_file_name\n", argv[]);
         return ;
     }

     file_name = argv[];

     ret = bitmap_file_generate(file_name, *, *);

     printf("bitmap_file_generate, ret: %d\n", ret);

     return ;
 }