Transparent 之 AlphaBlend

最新推荐文章于 2024-03-19 10:30:00 发布

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最新推荐文章于 2024-03-19 10:30:00 发布

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原文链接：http://www.cnblogs.com/dahai/archive/2011/07/11/2103030.html

本文详细介绍了AlphaBlend函数的使用方法，该函数用于显示具有透明或半透明像素的位图。通过示例代码展示了如何加载位图、获取位图信息，并使用AlphaBlend函数实现位图的透明叠加效果。

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函数:

The AlphaBlend function displays bitmaps that have transparent or semitransparent pixels.

BOOL AlphaBlend(
  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
  BLENDFUNCTION blendFunction  // alpha-blending function
);

代码:

	static HBITMAP hBmp1;
	static HBITMAP hBmp2;
	static int cxBmp;
	static int cyBmp;

	case WM_CREATE:
		{
			//load bmp
			hBmp1 = LoadBitmap(GetModuleHandle(NULL),MAKEINTRESOURCE(IDB_BITMAP1));
			if (hBmp1 == NULL)
			{
				MessageBox(hWnd,L"failed to load bmp1!",NULL,MB_OK);
			}
			hBmp2 = LoadBitmap(GetModuleHandle(NULL),MAKEINTRESOURCE(IDB_BITMAP2));
			if (hBmp2 == NULL)
			{
				MessageBox(hWnd,L"failed to load bmp2!",NULL,MB_OK);
			}
			//get bmp info
			BITMAP bmpInfo;
			GetObject(hBmp1,sizeof(BITMAP),&bmpInfo);
			cxBmp = bmpInfo.bmWidth;
			cyBmp = bmpInfo.bmHeight;
			//put window int the middle screen
			int cxScr = GetSystemMetrics(SM_CXSCREEN);
			int cyScr = GetSystemMetrics(SM_CYSCREEN);
			int cxWnd = cxBmp + 2 * GetSystemMetrics(SM_CXFRAME);
			int cyWnd = cyBmp + 2 * GetSystemMetrics(SM_CXFRAME) + GetSystemMetrics(SM_CYCAPTION);
			MoveWindow(hWnd,(cxScr-cxWnd)/2,(cyScr-cyWnd)/2,cxWnd,cyWnd,TRUE);
		}
		break;

	case WM_PAINT:
		hdc = BeginPaint(hWnd, &ps);
		{
			//disp bmp
			HDC hMemDC1 = CreateCompatibleDC(hdc);
			HDC hMemDC2 = CreateCompatibleDC(hdc);
			SelectObject(hMemDC1, hBmp1);
			SelectObject(hMemDC2, hBmp2);
			
			BLENDFUNCTION bf;
			bf.BlendOp = AC_SRC_OVER;
			bf.BlendFlags = 0;
			bf.SourceConstantAlpha = 128;//alpha transparency value
			bf.AlphaFormat = 0;
			AlphaBlend(hMemDC1,0,0,cxBmp,cyBmp,hMemDC2,0,0,cxBmp,cyBmp,bf);

			BitBlt(hdc, 0, 0,cxBmp, cyBmp, hMemDC1, 0, 0, SRCCOPY);			

			DeleteDC(hMemDC1);
			DeleteDC(hMemDC2);

		}
		EndPaint(hWnd, &ps);
		break;

结果:

转载于:https://www.cnblogs.com/dahai/archive/2011/07/11/2103030.html