类似于AlphaBlend，对24位位图进行透明混合

<textarea cols="50" rows="15" name="code" class="cpp">/*********************************************************************/ * * * Create24BPPDIBSection(HDC, int, int); * * * * Purpose: * * Creates a 24 bit-per-pixel DIB section with the specified * * width and height. * * * /*********************************************************************/ HBITMAP Create24BPPDIBSection(HDC hDC, int iWidth, int iHeight) { BITMAPINFO bmi; HBITMAP hbm; LPBYTE pBits; // Initialize header to 0s. ZeroMemory(&amp;bmi, sizeof(bmi)); // Fill out the fields you care about. bmi.bmiHeader.biSize = sizeof(BITMAPINFOHEADER); bmi.bmiHeader.biWidth = iWidth; bmi.bmiHeader.biHeight = iHeight; bmi.bmiHeader.biPlanes = 1; bmi.bmiHeader.biBitCount = 24; bmi.bmiHeader.biCompression = BI_RGB; // Create the surface. hbm = CreateDIBSection(hDC, &amp;bmi, DIB_RGB_COLORS, (void**)&amp;pBits, NULL, 0); return(hbm); } /*********************************************************************/ * * * BitmapsCompatible(LPBITMAP, LPBITMAP) * * * * Purpose: * * Compares two bitmap structures to see if the surfaces are * * the same width, height, and pixel format. * * * /*********************************************************************/ BOOL BitmapsCompatible(LPBITMAP lpbm1, LPBITMAP lpbm2) { if (lpbm1-&gt;bmBitsPixel != lpbm2-&gt;bmBitsPixel) return FALSE; if (lpbm1-&gt;bmPlanes != lpbm2-&gt;bmPlanes) return FALSE; if (lpbm1-&gt;bmWidth != lpbm2-&gt;bmWidth) return FALSE; if (lpbm1-&gt;bmHeight != lpbm2-&gt;bmHeight) return FALSE; return TRUE; } /*********************************************************************/ * * * BOOL BlendImages(HBITMAP, HBITMAP, HBITMAP, DWORD); * * * * Purpose: * * Blends two source images into a destination image * * using a specified weighting value for the first source * * image. * * * * Notes: * * All HBITMAP parameters must be 24 bit-per-pixel DIB sections. * * All HBITMAP parameters must have the same widths and heights. * * Weighting values must be in the range of 0 .. 255. * * * /*********************************************************************/ BOOL BlendImages(HBITMAP hbmSrc1, HBITMAP hbmSrc2, HBITMAP hbmDst, DWORD dwWeight1) { BITMAP bmSrc1, bmSrc2, bmDst; RGBTRIPLE *lprgbSrc1, *lprgbSrc2, *lprgbDst; DWORD dwWidthBytes, dwWeight2; int x, y; // Only values between 0 and 255 are valid. if (dwWeight1 &gt; 255) return FALSE; // Get weighting value for second source image. dwWeight2 = 255-dwWeight1; // Get information about the surfaces you were passed. if (!GetObject(hbmSrc1, sizeof(BITMAP), &amp;bmSrc1)) return FALSE; if (!GetObject(hbmSrc2, sizeof(BITMAP), &amp;bmSrc2)) return FALSE; if (!GetObject(hbmDst, sizeof(BITMAP), &amp;bmDst)) return FALSE; // Make sure you have data that meets your requirements. if (!BitmapsCompatible(&amp;bmSrc1, &amp;bmSrc2)) return FALSE; if (!BitmapsCompatible(&amp;bmSrc1, &amp;bmDst)) return FALSE; if (bmSrc1.bmBitsPixel != 24) return FALSE; if (bmSrc1.bmPlanes != 1) return FALSE; if (!bmSrc1.bmBits || !bmSrc2.bmBits || !bmDst.bmBits) return FALSE; dwWidthBytes = bmDst.bmWidthBytes; // Initialize the surface pointers. lprgbSrc1 = (RGBTRIPLE*)bmSrc1.bmBits; lprgbSrc2 = (RGBTRIPLE*)bmSrc2.bmBits; lprgbDst = (RGBTRIPLE*)bmDst.bmBits; for (y=0; y&lt;bmDst.bmHeight; y++) { for (x=0; x&lt;bmDst.bmWidth; x++) { lprgbDst[x].rgbtRed = (BYTE)((((DWORD)lprgbSrc1[x].rgbtRed * dwWeight1) + ((DWORD)lprgbSrc2[x].rgbtRed * dwWeight2)) &gt;&gt; 8); lprgbDst[x].rgbtGreen = (BYTE)((((DWORD)lprgbSrc1[x].rgbtGreen * dwWeight1) + ((DWORD)lprgbSrc2[x].rgbtGreen * dwWeight2)) &gt;&gt; 8); lprgbDst[x].rgbtBlue = (BYTE)((((DWORD)lprgbSrc1[x].rgbtBlue * dwWeight1) + ((DWORD)lprgbSrc2[x].rgbtBlue * dwWeight2)) &gt;&gt; 8); } // Move to next scan line. lprgbSrc1 = (RGBTRIPLE *)((LPBYTE)lprgbSrc1 + dwWidthBytes); lprgbSrc2 = (RGBTRIPLE *)((LPBYTE)lprgbSrc2 + dwWidthBytes); lprgbDst = (RGBTRIPLE *)((LPBYTE)lprgbDst + dwWidthBytes); } return TRUE; } /*********************************************************************/ * * * BOOL DoAlphaBlend() * * * * Purpose: * * Captures a copy of the source and destination areas and * * alpha blends them into a memory surface that it displays * * into the destination area. * * * * Notes: * * Takes the same parameters as the AlphaBlend function except * * that the last parameter is a source weighting value rather * * than a BLENDFUNCTION structure. * * * /*********************************************************************/ BOOL DoAlphaBlend( HDC hdcDest, // Handle to destination DC. int nXOriginDest, // X-coord of upper-left corner. int nYOriginDest, // Y-coord of upper-left corner. int nWidthDest, // Destination width. int nHeightDest, // Destination height. HDC hdcSrc, // Handle to source DC. int nXOriginSrc, // X-coord of upper-left corner. int nYOriginSrc, // Y-coord of upper-left corner. int nWidthSrc, // Source width. int nHeightSrc, // Source height. DWORD dwSourceWeight) // Source weighting (between 0 and 255). { HDC hdcSrc1 = NULL; HDC hdcSrc2 = NULL; HDC hdcDst = NULL; HBITMAP hbmSrc1 = NULL; HBITMAP hbmSrc2 = NULL; HBITMAP hbmDst = NULL; BOOL bReturn; // Create surfaces for sources and destination images. hbmSrc1 = Create24BPPDIBSection(hdcDest, nWidthDest,nHeightDest); if (!hbmSrc1) goto HANDLEERROR; hbmSrc2 = Create24BPPDIBSection(hdcDest, nWidthDest,nHeightDest); if (!hbmSrc2) goto HANDLEERROR; hbmDst = Create24BPPDIBSection(hdcDest, nWidthDest,nHeightDest); if (!hbmDst) goto HANDLEERROR; // Create HDCs to hold our surfaces. hdcSrc1 = CreateCompatibleDC(hdcDest); if (!hdcSrc1) goto HANDLEERROR; hdcSrc2 = CreateCompatibleDC(hdcDest); if (!hdcSrc2) goto HANDLEERROR; hdcDst = CreateCompatibleDC(hdcDest); if (!hdcDst) goto HANDLEERROR; // Prepare the surfaces for drawing. SelectObject(hdcSrc1, hbmSrc1); SelectObject(hdcSrc2, hbmSrc2); SelectObject(hdcDst, hbmDst); SetStretchBltMode(hdcSrc1, COLORONCOLOR); SetStretchBltMode(hdcSrc2, COLORONCOLOR); // Capture a copy of the source area. if (!StretchBlt(hdcSrc1, 0,0,nWidthDest,nHeightDest, hdcSrc, nXOriginSrc, nYOriginSrc, nWidthSrc, nHeightSrc, SRCCOPY)) goto HANDLEERROR; // Capture a copy of the destination area. if (!StretchBlt(hdcSrc2, 0,0,nWidthDest,nHeightDest, hdcDest, nXOriginDest, nYOriginDest, nWidthDest, nHeightDest, SRCCOPY)) goto HANDLEERROR; // Blend the two source areas to create the destination image. bReturn = BlendImages(hbmSrc1, hbmSrc2, hbmDst, dwSourceWeight); // Clean up objects you do not need any longer. // You cannot delete an object that's selected into an // HDC so delete the HDC first. DeleteDC(hdcSrc1); DeleteDC(hdcSrc2); DeleteObject(hbmSrc1); DeleteObject(hbmSrc2); // Display the blended (destination) image to the target HDC. if (bReturn) { BitBlt(hdcDest, nXOriginDest, nYOriginDest, nWidthDest, nHeightDest, hdcDst, 0,0, SRCCOPY); } // Clean up the rest of the objects you created. DeleteDC(hdcDst); DeleteObject(hbmDst); return bReturn; HANDLEERROR: if (hdcSrc1) DeleteDC(hdcSrc1); if (hdcSrc2) DeleteDC(hdcSrc2); if (hdcDst) DeleteDC(hdcDst); if (hbmSrc1) DeleteObject(hbmSrc1); if (hbmSrc2) DeleteObject(hbmSrc2); if (hbmDst) DeleteObject(hbmDst); return FALSE; } </textarea>