[英]Getting wrong data while reading Bitmap image
I'm following this tutorial http://www.gamedev.net/page/resources/_/technical/game-programming/how-to-load-a-bitmap-r1966 and I got the problem of wrong value for all the bitmap header/info that I load. 我正在按照本教程http://www.gamedev.net/page/resources/_/technical/game-programming/how-to-load-a-bitmap-r1966进行操作 ,但我发现所有我加载的位图标题/信息。
I've declared the structure to store the bitmap header, info 我已经声明了存储位图标题信息的结构
typedef struct BITMAPFILE_HEADER {
WORD bfType;
DWORD bfSize;
WORD bfReserved1;
WORD bfReserved2;
DWORD bfOffBits;
} BITMAPFILE_HEADER;
//Bitmap information header
//provides information specific to the image data
typedef struct BITMAPINFO_HEADER{
DWORD biSize;
LONG biWidth;
LONG biHeight;
WORD biPlanes;
WORD biBitCount;
DWORD biCompression;
DWORD biSizeImage;
LONG biXPelsPerMeter;
LONG biYPelsPerMeter;
DWORD biClrUsed;
DWORD biClrImportant;
} BITMAPINFO_HEADER;
//Colour palette
typedef struct RGB_QUAD {
BYTE rgbBlue;
BYTE rgbGreen;
BYTE rgbRed;
BYTE rgbReserved;
} RGB_QUAD;
After that I read the bitmap by using following codes: 之后,我通过使用以下代码读取位图:
FILE *in;
in = fopen("picture.bmp", "rb");
if (in == NULL)
{
printf("Error opening file\n");
}
else
{
BITMAPFILE_HEADER bmfh;
BITMAPINFO_HEADER bmih;
fread(&bmfh, sizeof(BITMAPFILE_HEADER), 1, in);
fread(&bmih, sizeof(BITMAPINFO_HEADER), 1, in);
if (bmih.biBitCount != 24)
printf("not 24");
}
My picture is 24-bit but when I run this program, it shows "not 24". 我的图片是24位的,但是当我运行该程序时,它显示为“ not 24”。 I try to debug it in Visual Studio then I saw the bmih.biBitCount
is 0
. 我尝试在Visual Studio中调试它,然后看到bmih.biBitCount
为0
。 In addition, the image width and height is wrong as well, the only correct data that I found in the header is the bmfh.bfType
which is 19778
. 另外,图像的宽度和高度也是错误的,我在标头中找到的唯一正确数据是bmfh.bfType
,它是19778
。
Anyone know what's wrong with my codes? 有人知道我的代码有什么问题吗? Again, I just want to read the bmp but not displaying it. 同样,我只想读取bmp而不显示它。
PS: Originally the picture is in JPEG format. PS:最初图片为JPEG格式。 I converted it to BMP format by using MS PAINT and re-save it in BMP format. 我使用MS PAINT将其转换为BMP格式,然后将其重新保存为BMP格式。 I wonder does it affect the values? 我想知道这会影响价值吗?
I would imagine that you ran into an alignment issue , because the compiler can choose to align data in a structure as he sees fit. 我想您会遇到对齐问题 ,因为编译器可以选择按他认为合适的方式对齐结构中的数据。 You can try to pack your struct, but I would suggest to read out every field and fill it in separately, it is more work, but it is clearer and avoids alignment issues. 您可以尝试打包您的结构,但是我建议您读出每个字段并将其分别填写,这是更多的工作,但是它更清晰并且避免了对齐问题。
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