实用BltBit实现透明色

[TaiJi1985]

实现类似下面的函数
int DrawBitMapWithMask(HDC destDC,HBITMAP bmp,COLORREF mask);

我在网上看到一些需要用mask图的，那样使用很不方便
能不能指定一个mask颜色就实现透明色阿?

（图中所有使用mask色的位置，都变成透明的）

请各位指教！

[striking]

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);
}

The following is an example of how the DrawTransparentBitmap function might be called:

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).

[TaiJi1985]

谢谢牛人，问题解决了。

牛！