Question

我最近制作了一个程序来读取BMP文件的fileheader和infoheader。我把它们打包如图所示，然后将它们打开，然后打印宽度和高度。不幸的是，宽度和高度不正确。我不知道为什么。也许有点/小端的问题？如果是这样，我不知道如何解决它。我正在GCC上编译并运行它。

#pragma pack(1)

typedef struct
{
    unsigned char fileMarker1;       /* 'B' */                       
    unsigned char fileMarker2;       /* 'M' */ 
    unsigned int   bfSize;             
    unsigned short unused1;           
    unsigned short unused2;           
    unsigned int   imageDataOffset;  /* Offset to the start of image data */
 }FILEHEADER;

 typedef struct                       
 { 
    unsigned int   biSize;            
    signed int     width;            /* Width of the image */ 
    signed int     height;           /* Height of the image */ 
    unsigned short planes;             
    unsigned short bitPix;             
    unsigned int   biCompression;      
    unsigned int   biSizeImage;        
    int            biXPelsPerMeter;    
    int            biYPelsPerMeter;    
    unsigned int   biClrUsed;          
    unsigned int   biClrImportant;     
 }INFOHEADER;

 #pragma pack()

.....

 fread( &header, sizeof(FILEHEADER), 1, image );

.....

 fread( &iheader, sizeof(INFOHEADER), 1, image );

.....

 printf("Width: %i\n", iheader.width);
 printf("Height: %i\n", iheader.height);

Answer 1

Windows位图文件确实存储为小端。因此，假设您的系统是big-endian，则需要在加载后反转每个2或4字节int值的字节顺序。这个IBM article描述了各种方法。

读取BMP标头，打包。读不正确的值

1 个答案: