C++ 绘制部分透明的GDI+;使用UpdateLayeredWindow将位图设置为无边框窗口
我试图创建一个具有半透明像素的非矩形窗口。图像不是来自PNG,而是使用GDI+调用动态绘制的 我按如下方式创建窗口:C++ 绘制部分透明的GDI+;使用UpdateLayeredWindow将位图设置为无边框窗口,c++,windows,gdi+,C++,Windows,Gdi+,我试图创建一个具有半透明像素的非矩形窗口。图像不是来自PNG,而是使用GDI+调用动态绘制的 我按如下方式创建窗口: WNDCLASSEX wc = WNDCLASSEX(); wc.cbSize = sizeof(wc); HINSTANCE instance = GetModuleHandle(nullptr); std::wstring classname(L"gditest ui window class"); if (!GetClassInfoEx(instance, classna
WNDCLASSEX wc = WNDCLASSEX();
wc.cbSize = sizeof(wc);
HINSTANCE instance = GetModuleHandle(nullptr);
std::wstring classname(L"gditest ui window class");
if (!GetClassInfoEx(instance, classname.c_str(), &wc)) {
//wc.cbSize;
//wc.style = CS_DROPSHADOW;
wc.lpfnWndProc = process_messages;
//wc.cbClsExtra;
//wc.cbWndExtra;
wc.hInstance = instance;
wc.hIcon;
wc.hCursor = LoadCursor(0, IDC_ARROW);
//wc.hbrBackground;
//wc.lpszMenuName;
wc.lpszClassName = classname.c_str();
wc.hIconSm;
if (!RegisterClassEx(&wc))
throw GetLastError();
}
m_window = CreateWindowEx(WS_EX_APPWINDOW | WS_EX_LAYERED,
classname.c_str(), L"User Interface",
WS_VISIBLE,
CW_USEDEFAULT, CW_USEDEFAULT, 640, 480,
HWND_DESKTOP, 0, instance, this);
if (!m_window)
throw GetLastError();
update_window();
update_window()函数如下所示:
void user_interface::update_window()
{
RECT r;
GetClientRect(m_window, &r);
Bitmap buf(r.right - r.left, r.bottom - r.top, PixelFormat32bppARGB);
Graphics gfx(&buf);
Rect rect(r.left, r.top, r.right - r.left, r.bottom - r.top);
SolidBrush b(Color(0x7f00ff00));
gfx.FillRectangle(&b, rect);
/* CLSID clsid;
UINT numbytes = 0, numenc = 0;
GetImageEncodersSize(&numenc, &numbytes);
std::vector<char> encoders(numbytes, 0);
ImageCodecInfo *encoderptr = (ImageCodecInfo *)&encoders[0];
GetImageEncoders(numenc, numbytes, encoderptr);
clsid = encoderptr[4].Clsid;
buf.Save(L"test.png", &clsid);
*/
HDC gfxdc = gfx.GetHDC();
HDC scrndc = GetDC(HWND_DESKTOP);
BLENDFUNCTION blend;
blend.BlendOp = AC_SRC_OVER;
blend.BlendFlags = 0;
blend.SourceConstantAlpha = 255;
blend.AlphaFormat = AC_SRC_ALPHA;
POINT src = POINT(), dst;
SIZE size;
GetWindowRect(m_window, &r);
dst.x = r.left;
dst.y = r.top;
size.cx = buf.GetWidth();
size.cy = buf.GetHeight();
if (!UpdateLayeredWindow(m_window, scrndc, &dst, &size, gfxdc, &src, 0, &blend, ULW_ALPHA)) {
throw GetLastError();
}
ReleaseDC(HWND_DESKTOP, scrndc);
gfx.ReleaseHDC(gfxdc);
}
void用户界面::更新窗口()
{
矩形r;
GetClientRect(m_窗口和r);
位图buf(右-左,右下-右上,像素格式32bppargb);
图形gfx(&buf);
Rect Rect(右左,右上,右右-右左,右下-右上);
SolidBrush b(颜色(0x7f00ff00));
gfx.FillRectangle(&b,rect);
/*CLSID-CLSID;
UINT numbytes=0,numen=0;
GetImageEncodersSize(&numenc,&numbytes);
std::矢量编码器(numbytes,0);
ImageCodecInfo*编码器=(ImageCodecInfo*)和编码器[0];
GetImageEncoder(numenc、numbytes、Encoder);
clsid=编码器RPTR[4]。clsid;
buf.Save(L“test.png”和&clsid);
*/
HDC gfxdc=gfx.GetHDC();
HDC scrndc=GetDC(HWND_桌面);
混合功能混合;
blend.BlendOp=AC\u SRC\u OVER;
blend.BlendFlags=0;
blend.SourceConstantAlpha=255;
blend.AlphaFormat=AC_SRC_ALPHA;
点src=点(),dst;
大小;
GetWindowRect(m_窗口和r);
dst.x=右左;
dst.y=r.top;
size.cx=buf.GetWidth();
size.cy=buf.GetHeight();
if(!UpdateLayeredWindow(m_窗口、scrndc和dst、大小、gfxdc和src、0和混合、ULW_ALPHA)){
抛出GetLastError();
}
ReleaseDC(HWND_桌面,scrndc);
gfx.ReleaseHDC(gfxdc);
}
注释后的代码将位图对象保存到PNG中,我编写PNG只是为了确认位图绘制正确
没有错误发生,但是屏幕上的结果不是我想要的。我得到的不是一个50%透明的绿色正方形,而是一个几乎看不见的白色正方形:
另一件奇怪的事情是,点击窗户会穿透到下面的任何东西,即使它稍微可见
我做错了什么?通过重写update\u window()方法,自己解决了这个问题:
void user_interface::update_window()
{
RECT r;
GetClientRect(m_window, &r);
HDC scrndc = GetDC(HWND_DESKTOP);
HDC memdc = CreateCompatibleDC(scrndc);
HBITMAP bmp = CreateCompatibleBitmap(scrndc, r.right - r.left, r.bottom - r.top);
HBITMAP oldbmp = (HBITMAP)SelectObject(memdc, bmp);
Graphics gfx(memdc);
Rect rect(r.left, r.top, r.right - r.left, r.bottom - r.top);
SolidBrush b(Color(0x7f00ff00));
gfx.FillRectangle(&b, rect);
BLENDFUNCTION blend;
blend.BlendOp = AC_SRC_OVER;
blend.BlendFlags = 0;
blend.SourceConstantAlpha = 255;
blend.AlphaFormat = AC_SRC_ALPHA;
POINT src = POINT(), dst;
SIZE size;
size.cx = r.right - r.left;
size.cy = r.bottom - r.top;
GetWindowRect(m_window, &r);
dst.x = r.left;
dst.y = r.top;
if (!UpdateLayeredWindow(m_window, scrndc, &dst, &size, memdc, &src, 0, &blend, ULW_ALPHA)) {
throw GetLastError();
}
SelectObject(memdc, oldbmp);
DeleteObject(bmp);
DeleteDC(memdc);
ReleaseDC(HWND_DESKTOP, scrndc);
}
也许这不是最有效的方法,但它确实有效。可能会使HBITMAP、memdc和图形对象保留更长时间。这一点留给读者做练习 UpdateLayeredWindow()的源位图必须与屏幕兼容,否则视觉效果取决于硬件。GDI和GDIplus似乎能够绘制到任何位图中,但bitblt操作通常无法处理不同的(即不兼容的)格式。原因是速度。 不幸的是,Windows文档并没有很清楚地指出这些事实