Windows DDB和DIB技术应用(3)--图元外边矩形检测
GDI/GDI+中只有对字体的外边框的测量,而没有提供对点,线,面,曲线的外边框获取函数。下面是本人利用DIB技术编写的探测简单图元,甚至也可以探测自己定义的复杂图元的外边矩形框的函数。本人已经测试,效果很棒。
bool GetFeatureRange(void *object, //自己定义的图元对象 CRect rect, // DIB屏幕大小CDC *pDC, //绘图设置 CRect &retVal // 检测范围){CDC memDC; //临时绘图设备COLORREF bkcolor = RGB(255,255,255); // 背景色//创建临时设备memDC.CreateCompatibleDC(pDC);// 建立一个与屏幕显示相同大小的DIB位图BITMAPINFO info;memset(&info.bmiHeader,0,sizeof(BITMAPINFOHEADER));info.bmiHeader.biSize = sizeof(BITMAPINFOHEADER);info.bmiHeader.biWidth = rect.Width();info.bmiHeader.biHeight = rect.Height();info.bmiHeader.biPlanes = 1;info.bmiHeader.biBitCount = 32;info.bmiHeader.biCompression = BI_RGB;PVOID pBits; // 位图数据指针HBITMAP hbitmap = CreateDIBSection(memDC.m_hDC,&info,DIB_RGB_COLORS,&pBits,0,0);HBITMAP hOldBitmap = (HBITMAP)memDC.SelectObject(hbitmap);// 使用背景色清除位图memDC.FillSolidRect(0,0,rect.Width(), rect.Height(), bkcolor); // 绘制图元 object->Draw(...); // 还原位图memDC.SelectObject(hOldBitmap); // 销毁临时绘图设备memDC.DeleteDC(); // 获取位图信息CBitmap *pBitmap = CBitmap::FromHandle(hbitmap);BITMAP bmp;pBitmap->GetBitmap(&bmp);BYTE *pixels = (BYTE*)bmp.bmBits;// 探测范围bool bExist = false;// DIB存储方向有下至上 颜色存储形式BGRBYTE r,g,b;for(int i = 0; i < bmp.bmHeight; i++){for(int j = 0; j < bmp.bmWidth; j++){b = *(pixels++);g = *(pixels++);r = *(pixels++);pixels++; //跳过透明度 位图像素占32位字节if(RGB(r,g,b) != bkcolor){if(bExist){retVal.top = i;if(retVal.left > j) retVal.left = j;if(retVal.right < j) retVal.right = j;}else{retVal.left = retVal.right = j;retVal.top = retVal.bottom = i;bExist = true;}}}}if(bExist) //调整与屏幕相同的坐标{retVal.top = bmp.bmHeight - retVal.top;retVal.bottom = bmp.bmHeight - retVal.bottom;}pBitmap->DeleteObject();return bExist;}
