3×2的bitmap为什么无法预览？而8x1的却可以

[WindTech]

无法预览，在windows画板中可以打开

代码是这样的：
//bitmap.cx = 3; bitmap.cy = 2
//strFileName = 3-2.bmp

long lBufferSize = bitmap.cx * bitmap.cy * 3;

HANDLE hf = CreateFile(strFileName, GENERIC_WRITE, FILE_SHARE_READ, NULL,
CREATE_ALWAYS, NULL, NULL );

if( hf == INVALID_HANDLE_VALUE )
return;

// write out the file header
//
BITMAPFILEHEADER bfh;
memset( &bfh, 0, sizeof( bfh ) );
bfh.bfType = 'MB';
bfh.bfSize = sizeof( bfh ) + lBufferSize + sizeof( BITMAPINFOHEADER );
bfh.bfOffBits = sizeof( BITMAPINFOHEADER ) + sizeof( BITMAPFILEHEADER );

DWORD dwWritten = 0;
WriteFile( hf, &bfh, sizeof( bfh ), &dwWritten, NULL );

// and the bitmap format
//
BITMAPINFOHEADER bih;
memset( &bih, 0, sizeof( bih ) );
bih.biSize = sizeof( bih );
bih.biWidth = bitmap.cx;
bih.biHeight = bitmap.cy;
bih.biPlanes = 1;
bih.biBitCount = 24;

dwWritten = 0;
WriteFile( hf, &bih, sizeof( bih ), &dwWritten, NULL );

// and the bits themselves
//
dwWritten = 0;
WriteFile( hf, pBuffer, lBufferSize, &dwWritten, NULL );
CloseHandle( hf );

[lambochan]

扫描线要4字节对齐,8x1当然正常,而3x2的:
long lBufferSize = bitmap.cx * bitmap.cy * 3;
是不能这么乘的.
=============================================
long WidthBytes = bitmap.cx * 3;
if(WidthBytes % 4 != 0)
WidthBytes = (WidthBytes / 4 + 1) * 4;
long lBufferSize = WidthBytes * bitmap.cy;
=================================================

[WindTech]

非常感谢，能再问下为什么 扫描线要4字节对齐？不熟悉