rotate_bitmap.shtml

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// GetRotatedBitmap	- Create a new bitmap with rotated image
// Returns		- Returns new bitmap with rotated image
// hDIB			- Device-independent bitmap to rotate
// radians		- Angle of rotation in radians
// clrBack		- Color of pixels in the resulting bitmap that do
//			  not get covered by source pixels
HANDLE GetRotatedBitmap( HANDLE hDIB, float radians, COLORREF clrBack )
{
	// Get source bitmap info
	BITMAPINFO &bmInfo = *(LPBITMAPINFO)hDIB ;
	int bpp = bmInfo.bmiHeader.biBitCount;		// Bits per pixel
	
	int nColors = bmInfo.bmiHeader.biClrUsed ? bmInfo.bmiHeader.biClrUsed : 
					1 << bpp;
	int nWidth = bmInfo.bmiHeader.biWidth;
	int nHeight = bmInfo.bmiHeader.biHeight;
	int nRowBytes = ((((nWidth * bpp) + 31) & ~31) / 8);

	// Make sure height is positive and biCompression is BI_RGB or BI_BITFIELDS
	DWORD &compression = bmInfo.bmiHeader.biCompression;
	if( nHeight < 0 || (compression!=BI_RGB && compression!=BI_BITFIELDS))
		return NULL;

	LPVOID lpDIBBits;
	if( bmInfo.bmiHeader.biBitCount > 8 )
		lpDIBBits = (LPVOID)((LPDWORD)(bmInfo.bmiColors +
			bmInfo.bmiHeader.biClrUsed) + 
			((compression == BI_BITFIELDS) ? 3 : 0));
	else
		lpDIBBits = (LPVOID)(bmInfo.bmiColors + nColors);

    
	// Compute the cosine and sine only once
	float cosine = (float)cos(radians);
	float sine = (float)sin(radians);

	// Compute dimensions of the resulting bitmap
	// First get the coordinates of the 3 corners other than origin
	int x1 = (int)(-nHeight * sine);
	int y1 = (int)(nHeight * cosine);
	int x2 = (int)(nWidth * cosine - nHeight * sine);
	int y2 = (int)(nHeight * cosine + nWidth * sine);
	int x3 = (int)(nWidth * cosine);
	int y3 = (int)(nWidth * sine);

	int minx = min(0,min(x1, min(x2,x3)));
	int miny = min(0,min(y1, min(y2,y3)));
	int maxx = max(x1, max(x2,x3));
	int maxy = max(y1, max(y2,y3));

	int w = maxx - minx;
	int h = maxy - miny;


	// Create a DIB to hold the result
	int nResultRowBytes = ((((w * bpp) + 31) & ~31) / 8);
	long len = nResultRowBytes * h;
	int nHeaderSize = ((LPBYTE)lpDIBBits-(LPBYTE)hDIB) ;
	HANDLE hDIBResult = GlobalAlloc(GMEM_FIXED,len+nHeaderSize);
	// Initialize the header information
	memcpy( (void*)hDIBResult, (void*)hDIB, nHeaderSize);
	BITMAPINFO &bmInfoResult = *(LPBITMAPINFO)hDIBResult ;
	bmInfoResult.bmiHeader.biWidth = w;
	bmInfoResult.bmiHeader.biHeight = h;
	bmInfoResult.bmiHeader.biSizeImage = len;

	LPVOID lpDIBBitsResult = (LPVOID)((LPBYTE)hDIBResult + nHeaderSize);

	// Get the back color value (index)
	ZeroMemory( lpDIBBitsResult, len );
	DWORD dwBackColor;
	switch(bpp)
	{
	case 1:	//Monochrome
		if( clrBack == RGB(255,255,255) )
			memset( lpDIBBitsResult, 0xff, len );
		break;
	case 4:
	case 8:	//Search the color table
		int i;
		for(i = 0; i < nColors; i++ )
		{
			if( bmInfo.bmiColors[i].rgbBlue ==  GetBValue(clrBack)
				&& bmInfo.bmiColors[i].rgbGreen ==  GetGValue(clrBack)
				&& bmInfo.bmiColors[i].rgbRed ==  GetRValue(clrBack) )
			{
				if(bpp==4) i = i | i<<4;
				memset( lpDIBBitsResult, i, len );
				break;
			}
		}
		// If not match found the color remains black
		break;
	case 16:
		// Windows95 supports 5 bits each for all colors or 5 bits for red & blue
		// and 6 bits for green - Check the color mask for RGB555 or RGB565
		if( *((DWORD*)bmInfo.bmiColors) == 0x7c00 )
		{
			// Bitmap is RGB555
			dwBackColor = ((GetRValue(clrBack)>>3) << 10) + 
					((GetRValue(clrBack)>>3) << 5) +
					(GetBValue(clrBack)>>3) ;
		}
		else
		{
			// Bitmap is RGB565
			dwBackColor = ((GetRValue(clrBack)>>3) << 11) + 
					((GetRValue(clrBack)>>2) << 5) +
					(GetBValue(clrBack)>>3) ;
		}
		break;
	case 24:
	case 32:
		dwBackColor = (((DWORD)GetRValue(clrBack)) << 16) | 
				(((DWORD)GetGValue(clrBack)) << 8) |
				(((DWORD)GetBValue(clrBack)));
		break;
	}


	// Now do the actual rotating - a pixel at a time
	// Computing the destination point for each source point
	// will leave a few pixels that do not get covered
	// So we use a reverse transform - e.i. compute the source point
	// for each destination point

	for( int y = 0; y < h; y++ )
	{
		for( int x = 0; x < w; x++ )
		{
			int sourcex = (int)((x+minx)*cosine + (y+miny)*sine);
			int sourcey = (int)((y+miny)*cosine - (x+minx)*sine);
			if( sourcex >= 0 && sourcex < nWidth && sourcey >= 0 
				&& sourcey < nHeight )
			{
				// Set the destination pixel
				switch(bpp)
				{
					BYTE mask;
				case 1:		//Monochrome
					mask = *((LPBYTE)lpDIBBits + nRowBytes*sourcey + 
						sourcex/8) & (0x80 >> sourcex%8);
					//Adjust mask for destination bitmap
					mask = mask ? (0x80 >> x%8) : 0;
					*((LPBYTE)lpDIBBitsResult + nResultRowBytes*(y) + 
								(x/8)) &= ~(0x80 >> x%8);
					*((LPBYTE)lpDIBBitsResult + nResultRowBytes*(y) + 
								(x/8)) |= mask;
					break;
				case 4:
					mask = *((LPBYTE)lpDIBBits + nRowBytes*sourcey + 
						sourcex/2) & ((sourcex&1) ? 0x0f : 0xf0);
					//Adjust mask for destination bitmap
					if( (sourcex&1) != (x&1) )
						mask = (mask&0xf0) ? (mask>>4) : (mask<<4);
					*((LPBYTE)lpDIBBitsResult + nResultRowBytes*(y) + 
							(x/2)) &= ~((x&1) ? 0x0f : 0xf0);
					*((LPBYTE)lpDIBBitsResult + nResultRowBytes*(y) + 
							(x/2)) |= mask;
					break;
				case 8:
					BYTE pixel ;
					pixel = *((LPBYTE)lpDIBBits + nRowBytes*sourcey + 
							sourcex);
					*((LPBYTE)lpDIBBitsResult + nResultRowBytes*(y) + 
							(x)) = pixel;
					break;
				case 16:
					DWORD dwPixel;
					dwPixel = *((LPWORD)((LPBYTE)lpDIBBits + 
							nRowBytes*sourcey + sourcex*2));
					*((LPWORD)((LPBYTE)lpDIBBitsResult + 
						nResultRowBytes*y + x*2)) = (WORD)dwPixel;
					break;
				case 24:
					dwPixel = *((LPDWORD)((LPBYTE)lpDIBBits + 
						nRowBytes*sourcey + sourcex*3)) & 0xffffff;
					*((LPDWORD)((LPBYTE)lpDIBBitsResult + 
						nResultRowBytes*y + x*3)) |= dwPixel;
					break;
				case 32:
					dwPixel = *((LPDWORD)((LPBYTE)lpDIBBits + 
						nRowBytes*sourcey + sourcex*4));
					*((LPDWORD)((LPBYTE)lpDIBBitsResult + 
						nResultRowBytes*y + x*4)) = dwPixel;
				}
			}
			else 
			{
				// Draw the background color. The background color
				// has already been drawn for 8 bits per pixel and less
				switch(bpp)
				{
				case 16:
					*((LPWORD)((LPBYTE)lpDIBBitsResult + 
						nResultRowBytes*y + x*2)) = 
						(WORD)dwBackColor;
					break;
				case 24:
					*((LPDWORD)((LPBYTE)lpDIBBitsResult + 
						nResultRowBytes*y + x*3)) |= dwBackColor;
					break;
				case 32:
					*((LPDWORD)((LPBYTE)lpDIBBitsResult + 
						nResultRowBytes*y + x*4)) = dwBackColor;
					break;
				}
			}
		}
	}

	return hDIBResult;
}
</FONT></TT></PRE>



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