Getting the dimensions of a bitmap

CodeGuru content and product recommendations are editorially independent. We may make money when you click on links to our partners. Learn More.

For CBitmap objects we can use the GetBitmap() function to determine the height and width of the bitmap.

	// The variable bitmap is a CBitmap object
	BITMAP bm;
	bitmap.GetBitmap( &bm );
	bmWidth = bm.bmWidth;
	bmHeight = bm.bmHeight;

If you have a HBITMAP, you can attach it to a CBitmap object and use the method shown above or you can use

	// The variable hBmp is a HBITMAP
	BITMAP bm;
	::GetObject( hBmp, sizeof( bm ), &bm );
	bmWidth = bm.bmWidth;
	bmHeight = bm.bmHeight;

For images in a BMP file, you can use something like

	CFile file;
	// sBMPFileName is the BMP filename
	if( !file.Open( sBMPFileName, CFile::modeRead) )
		return ;

	BITMAPFILEHEADER bmfHeader;

	// Read file header
	if (file.Read((LPSTR)&bmfHeader, sizeof(bmfHeader)) != sizeof(bmfHeader))
		return ;

	// File type should be 'BM'
	if (bmfHeader.bfType != ((WORD) ('M' << 8) | 'B'))
		return ;

	BITMAPINFOHEADER bmiHeader;
	if (file.Read((LPSTR)&bmiHeader, sizeof(bmiHeader)) != sizeof(bmiHeader))
		return ;


	int bmWidth = bmiHeader.biWidth;
	int bmHeight = bmiHeader.biHeight;