void DrawTransparentBitmap(HDC hdc, HBITMAP hBitmap, short xStart,short yStart, COLORREF cTransparentColor)
...{
BITMAP bm; COLORREF cColor; HBITMAP bmAndBack, bmAndObject, bmAndMem, bmSave; HBITMAP bmBackOld, bmObjectOld, bmMemOld, bmSaveOld; HDC hdcMem, hdcBack, hdcObject, hdcTemp, hdcSave; POINT ptSize; hdcTemp = CreateCompatibleDC(hdc); SelectObject(hdcTemp, hBitmap); // Select the bitmap GetObject(hBitmap, sizeof(BITMAP), (LPSTR)&bm); ptSize.x = bm.bmWidth; // Get width of bitmap ptSize.y = bm.bmHeight; // Get height of bitmap DPtoLP(hdcTemp, &ptSize, 1); // Convert from device // to logical points // Create some DCs to hold temporary data. hdcBack = CreateCompatibleDC(hdc); hdcObject = CreateCompatibleDC(hdc); hdcMem = CreateCompatibleDC(hdc); hdcSave = CreateCompatibleDC(hdc); // Create a bitmap for each DC. DCs are required for a number of // GDI functions. // Monochrome DC bmAndBack = CreateBitmap(ptSize.x, ptSize.y, 1, 1, NULL); // Monochrome DC bmAndObject = CreateBitmap(ptSize.x, ptSize.y, 1, 1, NULL); bmAndMem = CreateCompatibleBitmap(hdc, ptSize.x, ptSize.y); bmSave = CreateCompatibleBitmap(hdc, ptSize.x, ptSize.y); // Each DC must select a bitmap object to store pixel data. bmBackOld = (HBITMAP)::SelectObject(hdcBack, bmAndBack); bmObjectOld = (HBITMAP)::SelectObject(hdcObject, bmAndObject); bmMemOld = (HBITMAP)::SelectObject(hdcMem, bmAndMem); bmSaveOld = (HBITMAP)::SelectObject(hdcSave, bmSave); // Set proper mapping mode. SetMapMode(hdcTemp, GetMapMode(hdc)); // Save the bitmap sent here, because it will be overwritten. BitBlt(hdcSave, 0, 0, ptSize.x, ptSize.y, hdcTemp, 0, 0, SRCCOPY); // Set the background color of the source DC to the color. // contained in the parts of the bitmap that should be transparent cColor = SetBkColor(hdcTemp, cTransparentColor); // Create the object mask for the bitmap by performing a BitBlt // from the source bitmap to a monochrome bitmap. BitBlt(hdcObject, 0, 0, ptSize.x, ptSize.y, hdcTemp, 0, 0, SRCCOPY); // Set the background color of the source DC back to the original // color. SetBkColor(hdcTemp, cColor); // Create the inverse of the object mask. BitBlt(hdcBack, 0, 0, ptSize.x, ptSize.y, hdcObject, 0, 0, NOTSRCCOPY); // Copy the background of the main DC to the destination. BitBlt(hdcMem, 0, 0, ptSize.x, ptSize.y, hdc, xStart, yStart, SRCCOPY); // Mask out the places where the bitmap will be placed. BitBlt(hdcMem, 0, 0, ptSize.x, ptSize.y, hdcObject, 0, 0, SRCAND); // Mask out the transparent colored pixels on the bitmap. BitBlt(hdcTemp, 0, 0, ptSize.x, ptSize.y, hdcBack, 0, 0, SRCAND); // XOR the bitmap with the background on the destination DC. BitBlt(hdcMem, 0, 0, ptSize.x, ptSize.y, hdcTemp, 0, 0, SRCPAINT); // Copy the destination to the screen. BitBlt(hdc, xStart, yStart, ptSize.x, ptSize.y, hdcMem, 0, 0, SRCCOPY); // Place the original bitmap back into the bitmap sent here. BitBlt(hdcTemp, 0, 0, ptSize.x, ptSize.y, hdcSave, 0, 0, SRCCOPY); // Delete the memory bitmaps. DeleteObject(SelectObject(hdcBack, bmBackOld)); DeleteObject(SelectObject(hdcObject, bmObjectOld)); DeleteObject(SelectObject(hdcMem, bmMemOld)); DeleteObject(SelectObject(hdcSave, bmSaveOld)); // Delete the memory DCs. DeleteDC(hdcMem); DeleteDC(hdcBack); DeleteDC(hdcObject); DeleteDC(hdcSave); DeleteDC(hdcTemp);
}1.位图的旋转
如果你的应用程序仅工作在Windows NT下，那么你可以通过API函数旋转你的位图。
你或者使用world transformation和BitBlt()或者使用PlgBlt()旋转位图。一个
使用第一种方法的函数显示在下面。
如果你的目标是多平台的，那么你的任务变得非常困难。你只能通过旋转源位图中
每个象素或者直接操作DIB字节得到旋转位图。第一种方法通过每个点的处理是非
常慢的，第二种方法是很复杂的，但它有足够快的速度。注：下面的所有函数旋转
后产生新的位图，如果你需要直接绘制位图，请自已修改函数。 其中函数1仅工作
在NT环境下，它是最简单也是最快的，可惜它不支持Windows95。
所有的函数所接受的角度单位是弧度，如果是角度单位是度请用下面的公式转换。
radian = (2*pi *degree)/360
旋转步骤：
创建一对与设备兼容的显示设备。一个用于源位图，一个用于旋转后的目标位图。
预计算正弦和余弦函数值，这样可以避免重复计算。
用下面的公式计算旋转图像后的矩形
newx = x.cos(angle) + y.sin(angle)
newy = y.cos(angle) - x.sin(angle)
旋转后的位图将不能占用整个新位图，我们将用背景色填充它。
点阵转换公式
newx = x * eM11 + y * eM21 + eDx
newy = x * eM12 + y * eM22 + eDy
其中eM11和eM22是角度的余弦值，eM21是角度的正弦，eM12是eM21的负值。 eDx & eDy
目的是旋转后的位图在新的位图不被剪切。
函数一：适用于NT
// GetRotatedBitmapNT - Create a new bitmap with rotated image// Returns - Returns new bitmap with rotated image// hBitmap - Bitmap to rotate// radians - Angle of rotation in radians// clrBack - Color of pixels in the resulting bitmap that do// not get covered by source pixelsHBITMAP GetRotatedBitmapNT( HBITMAP hBitmap, float radians, COLORREF clrBack )...{ // Create a memory DC compatible with the display CDC sourceDC, destDC; sourceDC.CreateCompatibleDC( NULL ); destDC.CreateCompatibleDC( NULL ); // Get logical coordinates BITMAP bm; GetObject( hBitmap, sizeof( bm ), &bm ); 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)(bm.bmHeight * sine); int y1 = (int)(bm.bmHeight * cosine); int x2 = (int)(bm.bmWidth * cosine + bm.bmHeight * sine); int y2 = (int)(bm.bmHeight * cosine - bm.bmWidth * sine); int x3 = (int)(bm.bmWidth * cosine); int y3 = (int)(-bm.bmWidth * sine); int minx = min(0,min(x1, min(x2,x3))); int miny = min(0,min(y1, min(y2,y3))); int maxx = max(0,max(x1, max(x2,x3))); int maxy = max(0,max(y1, max(y2,y3))); int w = maxx - minx; int h = maxy - miny; // Create a bitmap to hold the result HBITMAP hbmResult = ::CreateCompatibleBitmap(CClientDC(NULL), w, h); HBITMAP hbmOldSource = (HBITMAP)::SelectObject( sourceDC.m_hDC, hBitmap ); HBITMAP hbmOldDest = (HBITMAP)::SelectObject( destDC.m_hDC, hbmResult ); // Draw the background color before we change mapping mode HBRUSH hbrBack = CreateSolidBrush( clrBack ); HBRUSH hbrOld = (HBRUSH)::SelectObject( destDC.m_hDC, hbrBack ); destDC.PatBlt( 0, 0, w, h, PATCOPY ); ::DeleteObject( ::SelectObject( destDC.m_hDC, hbrOld ) ); // We will use world transform to rotate the bitmap SetGraphicsMode(destDC.m_hDC, GM_ADVANCED); XFORM xform; xform.eM11 = cosine; xform.eM12 = -sine; xform.eM21 = sine; xform.eM22 = cosine; xform.eDx = (float)-minx; xform.eDy = (float)-miny; SetWorldTransform( destDC.m_hDC, &xform ); // Now do the actual rotating - a pixel at a time destDC.BitBlt(0,0,bm.bmWidth, bm.bmHeight, &sourceDC, 0, 0, SRCCOPY ); // Restore DCs SelectObject( sourceDC.m_hDC, hbmOldSource ); SelectObject( destDC.m_hDC, hbmOldDest ); return hbmResult;}
函数二: GetRotatedBitmap()使用 GetPixel & SetPixel
// GetRotatedBitmap - Create a new bitmap with rotated image// Returns - Returns new bitmap with rotated image// hBitmap - 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// Note - If the bitmap uses colors not in the system palette// then the result is unexpected. You can fix this by// adding an argument for the logical palette.HBITMAP GetRotatedBitmap( HBITMAP hBitmap, float radians, COLORREF clrBack )...{ // Create a memory DC compatible with the display CDC sourceDC, destDC; sourceDC.CreateCompatibleDC( NULL ); destDC.CreateCompatibleDC( NULL ); // Get logical coordinates BITMAP bm; GetObject( hBitmap, sizeof( bm ), &bm ); 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)(-bm.bmHeight * sine); int y1 = (int)(bm.bmHeight * cosine); int x2 = (int)(bm.bmWidth * cosine - bm.bmHeight * sine); int y2 = (int)(bm.bmHeight * cosine + bm.bmWidth * sine); int x3 = (int)(bm.bmWidth * cosine); int y3 = (int)(bm.bmWidth * 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 bitmap to hold the result HBITMAP hbmResult =CreateCompatibleBitmap(CClientDC(NULL), w, h); HBITMAP hbmOldSource = (HBITMAP)SelectObject( sourceDC.m_hDC, hBitmap ); HBITMAP hbmOldDest = (HBITMAP)SelectObject( destDC.m_hDC, hbmResult ); // Draw the background color before we change mapping mode HBRUSH hbrBack = CreateSolidBrush( clrBack ); HBRUSH hbrOld = (HBRUSH)SelectObject( destDC.m_hDC, hbrBack ); destDC.PatBlt( 0, 0, w, h, PATCOPY ); DeleteObject(SelectObject( destDC.m_hDC, hbrOld ) ); // Set mapping mode so that +ve y axis is upwords sourceDC.SetMapMode(MM_ISOTROPIC); sourceDC.SetWindowExt(1,1); sourceDC.SetViewportExt(1,-1); sourceDC.SetViewportOrg(0, bm.bmHeight-1); destDC.SetMapMode(MM_ISOTROPIC); destDC.SetWindowExt(1,1); destDC.SetViewportExt(1,-1); destDC.SetWindowOrg(minx, maxy); // 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 = miny; y < maxy; y++ )
...{ for( int x = minx; x < maxx; x++ ) ...{ int sourcex = (int)(x*cosine + y*sine); int sourcey = (int)(y*cosine - x*sine); if( sourcex >= 0 && sourcex < bm.bmWidth && sourcey >= 0 && sourcey < bm.bmHeight ) destDC.SetPixel(x,y,sourceDC.GetPixel(sourcex,sourcey));
}