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Jeremy
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 Posted: Fri Jan 02, 2004 3:10 am Post subject: Some quirks with sizeof(BITMAPFILEHEADER) |
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This may be in the wrong newsgroup, so let me apologize first.
I would like to ask if anyone else has had a problem attempting to load bitmap files without the aid of the VCL. This is code taken directly from my project, and the output beneath it: (in is defined as an ifstream)
BITMAPFILEHEADER bfh;
BITMAPINFOHEADER bih;
in.read((char *)&bfh,sizeof(BITMAPFILEHEADER));
in.read((char *)&bih,sizeof(BITMAPINFOHEADER));
cout << "Width: " << bih.biWidth << endl;
cout << "Height: " << bih.biHeight << endl;
cout << "sizeof(BITMAPFILEHEADER) = " << sizeof(BITMAPFILEHEADER) << endl;
cout << "sizeof(BITMAPINFOHEADER) = " << sizeof(BITMAPINFOHEADER) << endl;
Output:
Width: 1141120
Height: 65536
sizeof(BITMAPFILEHEADER) = 16
sizeof(BITMAPINFOHEADER) = 40
That's quite a huge bitmap! The main problem is with sizeof(BITMAPFILEHEADER) though. In wingdi.h (line 769), BITMAPFILEHEADER is defined as such:
typedef struct tagBITMAPFILEHEADER {
WORD bfType;
DWORD bfSize;
WORD bfReserved1;
WORD bfReserved2;
DWORD bfOffBits;
} BITMAPFILEHEADER, FAR *LPBITMAPFILEHEADER, *PBITMAPFILEHEADER;
Assuming that a word is 2 bytes and a dword is 4 bytes, this comes to 14, not 16. I'm guessing the compiler is padding everything so that it aligns correctly; however, the information is still wrong, and causes serious problems. I'm wondering, has anyone else run into this problem and knows a fix for it? I'm not adverse to using the actual sizes instead of sizeof(), but it's a hassle. Thanks!
BTW, when I use 14 instead of sizeof(BITMAPFILEHEADER), everything works. 
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Jeremy
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| Posted: Fri Jan 02, 2004 3:19 am Post subject: Re: Some quirks with sizeof(BITMAPFILEHEADER) |
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"Jeremy" <nychold (AT) yahoo (DOT) com> wrote:
<question clipped>
Oh, sorry...I should've said this. I've got Borland C++ Builder 6 running on Windows XP Professional.
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Tomasz Piasecki
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| Posted: Fri Jan 02, 2004 12:13 pm Post subject: Re: Some quirks with sizeof(BITMAPFILEHEADER) |
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Jeremy wrote:
| Quote: | I would like to ask if anyone else has had a problem attempting to load bitmap files without the aid of the VCL. This is code taken directly from my project, and the output beneath it: (in is defined as an ifstream)
Yes, I've had problems with this too. |
It was some time ago so I am nto 100% sure now that I remember results
of my ivestigation well, but I think the problem is that if you include
vcl.h or windows.h for definitions of BITMAPFILEINFOHEADER the 4-bytes
align is used.
I've resolved this by defining my own structure for both
BITMAPFILEHEADER and BITMAPINFOHEADER forcing 1-byte align first.
TP.
--
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_____ _| |_| | __ (o) | | __ __ @poczta.onet.pl |
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|_|_|_| _| |__/|_| |_|__|__||_| Tomasz Piasecki |
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Jeremy
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| Posted: Fri Jan 02, 2004 7:33 pm Post subject: Re: Some quirks with sizeof(BITMAPFILEHEADER) |
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Tomasz Piasecki <mtbrider (AT) _-nospam-_ (DOT) poczta.onet.pl> wrote:
| Quote: | Jeremy wrote:
I would like to ask if anyone else has had a problem attempting to load bitmap files without the aid of the VCL. This is code taken directly from my project, and the output beneath it: (in is defined as an ifstream)
Yes, I've had problems with this too.
It was some time ago so I am nto 100% sure now that I remember results
of my ivestigation well, but I think the problem is that if you include
vcl.h or windows.h for definitions of BITMAPFILEINFOHEADER the 4-bytes
align is used.
I've resolved this by defining my own structure for both
BITMAPFILEHEADER and BITMAPINFOHEADER forcing 1-byte align first.
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Well, I don't have vcl.h included in my source code. The only two files I have included are windows.h (which includes other windows header files) and gl/gl.h. (This is for a texture mapper, so stuff has to be accurate.)
And yes, when I defined my own structure and forced 1 byte alignment as you said, the sizeof() worked fine. However, I'd rather not do this. Alignment tends to make programs faster, and I need all the speed I can get. Maybe I'll just write some #define's or const int's for the structure sizes.
Thanks!
-- JT
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Tomasz Piasecki
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| Posted: Fri Jan 02, 2004 9:57 pm Post subject: Re: Some quirks with sizeof(BITMAPFILEHEADER) |
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Jeremy wrote:
| Quote: | And yes, when I defined my own structure and forced 1 byte alignment
as you said, the sizeof() worked fine. However, I'd rather not do
this. Alignment tends to make programs faster, and I need all the
speed I can get.
So change alignment only for type definition of this particular structure: |
#pragma pack(push,1) //push default alignment and set it to 1
struct TMyBitmapFileHeader
{
....
};
#pragma pack(pop) //pop default alignment
TP.
--
| Quote: | _ _ _ |
_____ _| |_| | __ (o) | | __ __ @poczta.onet.pl |
| | | |o | | |/o |/ _| |
|_|_|_| _| |__/|_| |_|__|__||_| Tomasz Piasecki |
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nicolasr
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| Posted: Sun Jan 04, 2004 2:55 am Post subject: Re: Some quirks with sizeof(BITMAPFILEHEADER) |
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Hi,
I had similar problems with BCB6. There seems to be
something wrong with a few header files. The pshpack*
headers seem to disturb structure alignment.
Try this link:
http://www.bcbdev.com/articles/bcb6headers.htm
hth,
Nick
| Quote: | "Jeremy" <nychold (AT) yahoo (DOT) com> wrote:
question clipped
Oh, sorry...I should've said this. I've got Borland C++ Builder 6 running
on Windows XP Professional. |
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Damon Chandler (TeamB)
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| Posted: Sat Jan 10, 2004 6:32 am Post subject: Re: Some quirks with sizeof(BITMAPFILEHEADER) |
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Jeremy,
| Quote: | BITMAPFILEHEADER bfh;
BITMAPINFOHEADER bih;
Width: 1141120
Height: 65536
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I had the same problems a few months back; cost me a several hours of
needless debugging. Download and install Update 4 for BCB6--that should
fix the problem.
Good luck,
Damon (TeamB)
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