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Re: StaticImage cannot show BMP file [message #43614 is a reply to message #43610]

Sat, 13 September 2014 20:18

hans
Messages: 44
Registered: March 2006
Location: Germany

Member

Hi, your struct BMP_FILEHEADER has the wrong memory layout,
it must be "packed" meaning no gaps between the members.

You have:

struct BMP_FILEHEADER {
	word    bfType;       2 bytes
gap-------------------------->2 bytes
	dword   bfSize;       4 bytes
	word    bfReserved1;  2 bytes
	word    bfReserved2;  2 bytes
	dword   bfOffBits;    4 bytes

In sum                       16 bytes

but the Microsoft spec requires that no gap between members exists (in the time defining the struct it was traded not to "waste" space often).

So it must be

struct BMP_FILEHEADER {
	word    bfType;       2 bytes
	dword   bfSize;       4 bytes
	word    bfReserved1;  2 bytes
	word    bfReserved2;  2 bytes
	dword   bfOffBits;    4 bytes

In sum                       14 bytes

Your change to get it work (bfOffBits changing type) is not right, because
you have still bfSize member at invalid memory position.

The upp code tries to get the "packed" aligment by using for Microsoft Compiler

#ifdef COMPILER_MSC
#pragma pack(push, 1)
#endif

or for GCC

#ifdef COMPILER_GCC
__attribute__((packed))
#endif

You can check if the right compiler #define is defined.
Or your compiler ignores this directive for whatever reason.

Hope it helps.

[Updated on: Sat, 13 September 2014 23:30]

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