Hi,
I found this function for rotating the bitmap but I dont know what I'm supposed to do with the result. ie, how to implement it.
Can anyone shed any light on this please?
Thanks
Code:
// 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;
}
