main.cpp

本程序实现将一个位图转换成一个区域的功能

// Windows Header Files:
#include <windows.h>
#include "resource.h"


TCHAR szClassName[] = "WIN32TEST";

HBITMAP hBmp;

LRESULT CALLBACK WndProc(HWND hWnd, UINT message, WPARAM wParam, LPARAM lParam)
{
	PAINTSTRUCT ps;
	HDC hdc;

	switch (message) 
	{
		case WM_NCHITTEST:
			return HTCAPTION;

		case WM_LBUTTONDOWN:
			break;

		case WM_PAINT:
				hdc = BeginPaint (hWnd, &ps);
				if (hBmp)
				{
					BITMAP bm;
					GetObject(hBmp, sizeof(bm), &bm);

					HDC memdc = CreateCompatibleDC(NULL);
					HBITMAP h = (HBITMAP)SelectObject(memdc, hBmp);
					BitBlt(hdc, 0, 0, bm.bmWidth, bm.bmHeight, memdc, 0, 0, SRCCOPY);
					SelectObject(memdc, h);
				}
				EndPaint (hWnd, &ps);
			break;

		case WM_KEYDOWN:
			if (wParam != VK_ESCAPE)
				break;
			// Fall thru

		case WM_DESTROY:
				PostQuitMessage(0);
			break;

		default:
			return (DefWindowProc(hWnd, message, wParam, lParam));
	}
	
	return (0);
}



//
//	BitmapToRegion :	Create a region from the "non-transparent" pixels of a bitmap
//	Author :			Jean-Edouard Lachand-Robert (http://www.geocities.com/Paris/LeftBank/1160/resume.htm), June 1998.
//
//	hBmp :				Source bitmap
//	cTransparentColor :	Color base for the "transparent" pixels (default is black)
//	cTolerance :		Color tolerance for the "transparent" pixels.
//
//	A pixel is assumed to be transparent if the value of each of its 3 components (blue, green and red) is 
//	greater or equal to the corresponding value in cTransparentColor and is lower or equal to the 
//	corresponding value in cTransparentColor + cTolerance.
//
HRGN BitmapToRegion (HBITMAP hBmp, COLORREF cTransparentColor = 0, COLORREF cTolerance = 0x101010)
{
	HRGN hRgn = NULL;

	if (hBmp)
	{
		// Create a memory DC inside which we will scan the bitmap content
		HDC hMemDC = CreateCompatibleDC(NULL);
		if (hMemDC)
		{
			// Get bitmap size
			BITMAP bm;
			GetObject(hBmp, sizeof(bm), &bm);

			// Create a 32 bits depth bitmap and select it into the memory DC 
			BITMAPINFOHEADER RGB32BITSBITMAPINFO = {	
					sizeof(BITMAPINFOHEADER),	// biSize 
					bm.bmWidth,					// biWidth; 
					bm.bmHeight,				// biHeight; 
					1,							// biPlanes; 
					32,							// biBitCount 
					BI_RGB,						// biCompression; 
					0,							// biSizeImage; 
					0,							// biXPelsPerMeter; 
					0,							// biYPelsPerMeter; 
					0,							// biClrUsed; 
					0							// biClrImportant; 
			};
			VOID * pbits32; 
			HBITMAP hbm32 = CreateDIBSection(hMemDC, (BITMAPINFO *)&RGB32BITSBITMAPINFO, DIB_RGB_COLORS, &pbits32, NULL, 0);
			if (hbm32)
			{
				HBITMAP holdBmp = (HBITMAP)SelectObject(hMemDC, hbm32);

				// Create a DC just to copy the bitmap into the memory DC
				HDC hDC = CreateCompatibleDC(hMemDC);
				if (hDC)
				{
					// Get how many bytes per row we have for the bitmap bits (rounded up to 32 bits)
					BITMAP bm32;
					GetObject(hbm32, sizeof(bm32), &bm32);
					while (bm32.bmWidthBytes % 4)
						bm32.bmWidthBytes++;

					// Copy the bitmap into the memory DC
					HBITMAP holdBmp = (HBITMAP)SelectObject(hDC, hBmp);
					BitBlt(hMemDC, 0, 0, bm.bmWidth, bm.bmHeight, hDC, 0, 0, SRCCOPY);

					// For better performances, we will use the ExtCreateRegion() function to create the
					// region. This function take a RGNDATA structure on entry. We will add rectangles by
					// amount of ALLOC_UNIT number in this structure.
					#define ALLOC_UNIT	100
					DWORD maxRects = ALLOC_UNIT;
					HANDLE hData = GlobalAlloc(GMEM_MOVEABLE, sizeof(RGNDATAHEADER) + (sizeof(RECT) * maxRects));
					RGNDATA *pData = (RGNDATA *)GlobalLock(hData);
					pData->rdh.dwSize = sizeof(RGNDATAHEADER);
					pData->rdh.iType = RDH_RECTANGLES;
					pData->rdh.nCount = pData->rdh.nRgnSize = 0;
					SetRect(&pData->rdh.rcBound, MAXLONG, MAXLONG, 0, 0);

					// Keep on hand highest and lowest values for the "transparent" pixels
					BYTE lr = GetRValue(cTransparentColor);
					BYTE lg = GetGValue(cTransparentColor);
					BYTE lb = GetBValue(cTransparentColor);
					BYTE hr = min(0xff, lr + GetRValue(cTolerance));
					BYTE hg = min(0xff, lg + GetGValue(cTolerance));
					BYTE hb = min(0xff, lb + GetBValue(cTolerance));

					// Scan each bitmap row from bottom to top (the bitmap is inverted vertically)
					BYTE *p32 = (BYTE *)bm32.bmBits + (bm32.bmHeight - 1) * bm32.bmWidthBytes;
					for (int y = 0; y < bm.bmHeight; y++)
					{
						// Scan each bitmap pixel from left to right
						for (int x = 0; x < bm.bmWidth; x++)
						{
							// Search for a continuous range of "non transparent pixels"
							int x0 = x;
							LONG *p = (LONG *)p32 + x;
							while (x < bm.bmWidth)
							{
								BYTE b = GetRValue(*p);
								if (b >= lr && b <= hr)
								{
									b = GetGValue(*p);
									if (b >= lg && b <= hg)
									{
										b = GetBValue(*p);
										if (b >= lb && b <= hb)
											// This pixel is "transparent"
											break;
									}
								}
								p++;
								x++;
							}

							if (x > x0)
							{
								// Add the pixels (x0, y) to (x, y+1) as a new rectangle in the region
								if (pData->rdh.nCount >= maxRects)
								{
									GlobalUnlock(hData);
									maxRects += ALLOC_UNIT;
									hData = GlobalReAlloc(hData, sizeof(RGNDATAHEADER) + (sizeof(RECT) * maxRects), GMEM_MOVEABLE);
									pData = (RGNDATA *)GlobalLock(hData);
								}
								RECT *pr = (RECT *)&pData->Buffer;
								SetRect(&pr[pData->rdh.nCount], x0, y, x, y+1);
								if (x0 < pData->rdh.rcBound.left)
									pData->rdh.rcBound.left = x0;
								if (y < pData->rdh.rcBound.top)
									pData->rdh.rcBound.top = y;
								if (x > pData->rdh.rcBound.right)
									pData->rdh.rcBound.right = x;
								if (y+1 > pData->rdh.rcBound.bottom)
									pData->rdh.rcBound.bottom = y+1;
								pData->rdh.nCount++;

								// On Windows98, ExtCreateRegion() may fail if the number of rectangles is too
								// large (ie: > 4000). Therefore, we have to create the region by multiple steps.
								if (pData->rdh.nCount == 2000)
								{
									HRGN h = ExtCreateRegion(NULL, sizeof(RGNDATAHEADER) + (sizeof(RECT) * maxRects), pData);
									if (hRgn)
									{
										CombineRgn(hRgn, hRgn, h, RGN_OR);
										DeleteObject(h);
									}
									else
										hRgn = h;
									pData->rdh.nCount = 0;
									SetRect(&pData->rdh.rcBound, MAXLONG, MAXLONG, 0, 0);
								}
							}
						}

						// Go to next row (remember, the bitmap is inverted vertically)
						p32 -= bm32.bmWidthBytes;
					}

					// Create or extend the region with the remaining rectangles
					HRGN h = ExtCreateRegion(NULL, sizeof(RGNDATAHEADER) + (sizeof(RECT) * maxRects), pData);
					if (hRgn)
					{
						CombineRgn(hRgn, hRgn, h, RGN_OR);
						DeleteObject(h);
					}
					else
						hRgn = h;

					// Clean up
					SelectObject(hDC, holdBmp);
					DeleteDC(hDC);
				}

				DeleteObject(SelectObject(hMemDC, holdBmp));
			}

			DeleteDC(hMemDC);
		}	
	}

	return hRgn;
}


int APIENTRY WinMain(HINSTANCE hInstance,
                     HINSTANCE hPrevInstance,
                     LPSTR     lpCmdLine,
                     int       nCmdShow)
{
	WNDCLASS wc;
	HWND hWnd;
	MSG msg;

	hBmp = (HBITMAP)LoadImage(hInstance, MAKEINTRESOURCE(IDB_BITMAP1), IMAGE_BITMAP, 0, 0, LR_CREATEDIBSECTION);
	if (hBmp)
	{
		ZeroMemory(&wc, sizeof(wc));
		wc.style         = CS_HREDRAW | CS_VREDRAW;
		wc.lpszClassName = szClassName;
		wc.lpfnWndProc   = (WNDPROC)WndProc;
		wc.hInstance     = hInstance;

		if (RegisterClass(&wc))
		{
			BITMAP bm;
			GetObject(hBmp, sizeof(bm), &bm);

			hWnd = CreateWindow(szClassName, NULL, WS_POPUP, 0, 0, bm.bmWidth, bm.bmHeight, NULL, NULL, hInstance, NULL);
			if (hWnd)
			{
				HRGN h = BitmapToRegion(hBmp);
				if (h)
					SetWindowRgn(hWnd, h, TRUE);

				ShowWindow(hWnd, nCmdShow);
				UpdateWindow(hWnd);

				// Main message loop:
				while (GetMessage(&msg, NULL, 0, 0)) 
				{
					TranslateMessage(&msg);
					DispatchMessage(&msg);
				}

				return (msg.wParam);
			}
		}
	}

	return -1;
}