一种比较简单但比较慢的方法是逐个画点, CBitmap bmp;
CDC dc;
CPaintDC pdc( this ); bmp.LoadBitmap( IDB_BACK );
dc.CreateCompatibleDC( &pdc );
dc.SelectObject( &bmp ); int x, y;
for( x = 0; x < BMP_WIDTH; x++ )
{
for( y = 0; y < BMP_HIGEHT; y++ )
{
COLORREF pix;
pix = dc.GetPixel();
if( pix != RGB( 透明色 ) )
{
pdc.SetPixel( x, y, pix );
}
}
} 当然你应该获得图像的尺寸. 还有一种方式摘抄如下: 绘制“透明”位图是指绘制某一位图中除指定颜色外的其余部分，我们称这种颜色为“透明色”。通过将位图的背景色指定为“透明色”，在绘制时，不绘制这部分背景，而仅绘制图像，这样就可以将位图中图像透明地绘制到窗口上。 绘制“透明”位图的关键是创建一个“掩码”位图(mask bitmap)，“掩码”位图是一个单色位图，它是位图中图像的一个单色剪影。 在Windows编程中，绘图都要用到设备描述表，我们需创建两个内存设备描述表：位图设备描述表(image DC)和“掩码”位图设备描述表(mask DC)。位图设备描述表用来装入位图，而“掩码”位图设备描述表用来装入“掩码”位图。在“掩码”位图设备描述表中制作“掩码”位图的方式是：先创建一个单色的Bitmap，装入mask DC，然后，以“SRCCOPY”的方式将装有位图的位图设备描述表绘制(BitBlt)到mask DC上。这样，mask DC的显示平面中的位图即是“掩码”位图。 绘制“透明”位图的实际操作步骤： 1.将位图设备描述表以“SRCINVERT”的方式绘制(BitBlt)到显示设备描述表上； 2.将“掩码”位图设备描述表以“SRCAND”的方式绘制(BitBlt)到显示设备描述表上； 3.再将位图设备描述表以“SRCINVERT”的方式绘制(BitBlt)到显示设备描述表上。这样除“透明色”外的其余位图部分(图像部分)就被绘制到窗口上了。
如何设置bmp的mask，请明示
非常感谢你的这一段帖子，我将试一试，你的那一段摘抄源自何处，请告之
SourceDC.SetTextColor( RGB(255,255,255) );
SourceDC.DrawText( strTime, &CRect(0, 0, m_w, m_h), DT_CENTER | DT_VCENTER | DT_SINGLELINE );
ClockDC1.BitBlt(0, 0, m_w, m_h, &ClockDC, 0, 0, NOTSRCCOPY );
ClockDC1.BitBlt(0, 0, m_w, m_h, &SourceDC, 0, 0, NOTSRCERASE );
SourceDC.BitBlt( 0, 0, m_w, m_h, &alphaDC, 0, 0, SRCAND );
SourceDC.BitBlt( 0, 0, m_w, m_h, &ClockDC1, 0, 0, SRCPAINT );
return pDC->BitBlt( m_xPos, m_yPos, m_w, m_h, &SourceDC, 0, 0, SRCCOPY );
BOOL Create( UINT nBitmapID, int cx, int nGrow, COLORREF crMask );BOOL Create( LPCTSTR lpszBitmapID, int cx, int nGrow, COLORREF crMask );COLORREF crMask 为要去掉的bmp的背景色
调用方法见最下面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 = SelectObject(hdcBack, bmAndBack);
bmObjectOld = SelectObject(hdcObject, bmAndObject);
bmMemOld = SelectObject(hdcMem, bmAndMem);
bmSaveOld = 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);
} 可以这样调用 DrawTransparentBitmap(hdc, // The destination DC. hBitmap, // The bitmap to be drawn.
xPos, // X coordinate.
yPos, // Y coordinate.
0x00FFFFFF); // The color for transparent
// pixels (white, in this
// example).