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[ASP.net教程]UWP中的Direct2D


介绍

DirectX一直是Windows平台中高性能图形的代名词,自Win7开始,微软又推出了Direct2D技术,包装于Direct3D,但专注于2D图形,并且准备取代GDI这样的传统2D图形技术。对于Direct2D是怎么怎么好的具体描述,可以参考附录1.

不过Direct2D是基于COM技术的,看上去有些老旧的气息,而且是非托管的,似乎也和常见的.net语言有些隔阂。

不过微软也为我们提供了一个工具,一个跨越这一边界的工具,那就是SurfaceImageSource一族。该族中SurfaceImageSource继承自Windows.UI.Xaml.Media.ImageSource,VirtualSurfaceImageSource则继承自SurfaceImageSource,它们和BitmapSource在托管领域有着同样的地位。但同时这两个类又将触角伸到了COM的领域,分别可以query interface至ISurfaceImageSourceNative和IVirtualSurfaceImageSourceNative,再与Direct2D技术接轨。至此,XAML快速的界面技术,Direct2D高效的图形功能,得以合二为一。

本文将简单的介绍一下SurfaceImageSource的使用,为大家呈现一个高效图形应用的小例子(演示代码使用XAML和C++/CX)。

 

准备

代码主要是C++的(略有C++/CX扩展),因为要操作Direct2D和COM。大家可以根据需要自行包装自己的组件来调用。

用到了WIC(Windows Imaging Component)等技术,不过不是本文重点。

 

问题

熟悉WPF的读者可能想到,在classical desktop中使用的WPF,里面的一部分组件有一个神奇的属性,OpacityMask,利用它可以给控件的渲染显示加上一个蒙版,实现各种透明渐变和不规则轮廓等等。

不过到了UWP(更早的从Windows Store App出现开始),虽然大家写的还是一样的XAML,但是OpacityMask属性没了。估计是为了性能考虑吧,不给用这么繁琐的东西了。

但难免有时要用到这样的功能,我们可以依靠高效的Direct2D图形技术来实现它。

看看效果先:

 

托管的SurfaceImageSource

上文已经提到了,SurfaceImageSource是Windows.UI.Xaml.Media.ImageSource的子类,可以像使用BitmapSource一样使用它,赋给BitmatBrush的ImageSource什么的。这有点像WriteableBitmap,不过它却是操作Direct2D的入口。

 

我们先用XAML做一个这样的界面:

 1 <Page x:Class="App2.MainPage" 2    ="http://schemas.microsoft.com/winfx/2006/xaml/presentation" 3    ="http://schemas.microsoft.com/winfx/2006/xaml" 4    ="using:App2" 5    ="http://schemas.microsoft.com/expression/blend/2008" 6    ="http://schemas.open 7    mc:Ignorable="d"> 8  9   <Grid Background="{ThemeResource ApplicationPageBackgroundThemeBrush}">10     <Grid.RowDefinitions>11       <RowDefinition Height="50" />12       <RowDefinition Height="*" />13     </Grid.RowDefinitions>14 15     <Grid.Resources>16       <Style TargetType="Button">17         <Setter Property="Margin" Value="10,0,0,0" />18       </Style>19     </Grid.Resources>20 21     <StackPanel HorizontalAlignment="Center"22           Orientation="Horizontal"23           x:Name="btns">24       <Button Tag="Assets/star.png">Star</Button>25       <Button Tag="Assets/ellipse.png">Ellipse</Button>26     </StackPanel>27 28     <Rectangle Grid.Row="1" x:Name="canvas" />29   </Grid>30 </Page>

Button的Tag记载的是用来做蒙版的图片,我们的例子里使用的图片,为了方便都是400*400的。并且这两个蒙版图片都是用黑白表示的。黑色表示没有,白色表示全有,灰色就是半透明了,操作的是Alpha通道。

 

这分别是要显示的图片,和两种蒙版。

 

先看看MainPage声明了哪些成员:

1 Microsoft::WRL::ComPtr<IWICImagingFactory> m_factory; // WIC工厂,因为多处使用,可以复用一下2 Microsoft::WRL::ComPtr<IDXGIDevice> m_dxgiDevice; // DXGI Device3 Microsoft::WRL::ComPtr<ID2D1DeviceContext> m_d2dDeviceContext; // D2D Device Context4 Microsoft::WRL::ComPtr<IWICBitmapSource> m_img; // 这个就是要被蒙版处理的原始图片了

我们善用ComPtr,让C++的RAII机制(资源获取就是初始化)来帮我们实现简单的“垃圾回收”。

 

在MainPage::CreateDevice函数中,我们初始化Direct2D的相关设备:

void MainPage::CreateDevice(){  static D3D_FEATURE_LEVEL featureLevels[] =  {    D3D_FEATURE_LEVEL_11_1,    D3D_FEATURE_LEVEL_11_0,    D3D_FEATURE_LEVEL_10_1,    D3D_FEATURE_LEVEL_10_0,    D3D_FEATURE_LEVEL_9_3,    D3D_FEATURE_LEVEL_9_2,    D3D_FEATURE_LEVEL_9_1  };  HRESULT hr;  ComPtr<ID3D11Device> d3dDevice;  HR(D3D11CreateDevice(nullptr,    D3D_DRIVER_TYPE_HARDWARE,    0,    D3D11_CREATE_DEVICE_BGRA_SUPPORT, // 注意,Direct2D画图是BGRA通道顺序,不是常见的RGB    featureLevels,    extent<decltype(featureLevels)>::value, // C++ type traits,获取array长度    D3D11_SDK_VERSION,    &d3dDevice,    nullptr,    nullptr));  HR(d3dDevice.As(&m_dxgiDevice));  HR(D2D1CreateDevice(m_dxgiDevice.Get(), nullptr, &m_d2dDevice));  HR(m_d2dDevice->CreateDeviceContext(D2D1_DEVICE_CONTEXT_OPTIONS_NONE, &m_d2dDeviceContext));}

 

然后我们看看主要的画图流程:

这是那两个有蒙版设置的button,它们的Tag属性记录了要应用的蒙版的路径。

void MainPage::OnButtonClick(Object^ sender, RoutedEventArgs^ e){  HRESULT hr;  auto btn = safe_cast<Button^>(sender);  auto maskPath = btn->Tag->ToString();  SurfaceImageSource^ sis = ref new SurfaceImageSource(400, 400); // SurfaceImageSource创建时就必须指定大小,这个大小相当于画纸的大小  ComPtr<ISurfaceImageSourceNative> sisn;  // 跨越托管和非托管的边界  // 转换成IUnknown*也可以  HR(reinterpret_cast<IInspectable*>(sis)->QueryInterface(IID_PPV_ARGS(&sisn)));  HR(sisn->SetDevice(m_dxgiDevice.Get()));  // 这里需要注意,尽管SurfaceImageSource本身是个ImageSource,但是我们也应该在ImageBrush的层面上完成操作。如果我们将ImageBrush留在XAML上,而只新建和替换(在之后的流程里)SurfaceImageSource,会发生SurfaceImageSource赋值给ImageSource后引用计数增加量,和将ImageSource设为nullptr后引用计数减少量不相等的情况,发生“内存泄漏”。  auto brush = ref new ImageBrush();  brush->ImageSource = sis;  canvas->Fill = brush;  Draw(sisn.Get(), maskPath->Data());}

 

Draw函数。画图的操作我们需要在UI线程上完成:

void MainPage::Draw(ISurfaceImageSourceNative* sisn, const wchar_t* mask){  HRESULT hr;  ComPtr<IDXGISurface> surface;  RECT rect = { 0, 0, 400, 400 };  POINT renderTargetOffset; // 可视区域在surface中的偏移量  // 可以想象成surface是一张大画板,比我们的显示区域400*400要大。每次Direct2D会选择一个区域来画,不一定是(0,0),因为可能有一些缓冲策略,使得每次画图的区域都不一样  HR(PrepareDraw(sisn, rect, &surface, &renderTargetOffset));  // 创建所有我们需要的图形  ComPtr<IWICBitmapSource> maskSrc = GetMask(LoadImageByWIC(mask).Get());  ComPtr<ID2D1Bitmap> maskBmp;  ComPtr<ID2D1Bitmap> imgBmp;  ComPtr<ID2D1BitmapBrush> imgBrush;  ComPtr<ID2D1Bitmap1> tgrBmp; // Note ID2D1Bitmap1  HR(m_d2dDeviceContext->CreateBitmapFromWicBitmap(maskSrc.Get(), &maskBmp));  HR(m_d2dDeviceContext->CreateBitmapFromWicBitmap(m_img.Get(), &imgBmp));  HR(m_d2dDeviceContext->CreateBitmapBrush(imgBmp.Get(), &imgBrush));  HR(m_d2dDeviceContext->CreateBitmapFromDxgiSurface(surface.Get(), nullptr, &tgrBmp));  m_d2dDeviceContext->SetTarget(tgrBmp.Get());  m_d2dDeviceContext->BeginDraw();  m_d2dDeviceContext->SetTransform(D2D1::Matrix3x2F::Translation(renderTargetOffset.x, renderTargetOffset.y)); // 应用可视区域的偏移量来调整device context的位置  m_d2dDeviceContext->Clear({0, 0, 1, 1}); // 将画布填充成蓝色,让我们的改变变得明显一些    m_d2dDeviceContext->SetAntialiasMode(D2D1_ANTIALIAS_MODE_ALIASED); // 必须先设置这个,才能调用下面的函数  m_d2dDeviceContext->FillOpacityMask(maskBmp.Get(), imgBrush.Get()); // 应用蒙版  HR(m_d2dDeviceContext->EndDraw());  m_d2dDeviceContext->SetTarget(nullptr);  HR(sisn->EndDraw());}

 

以下是我们的一些辅助函数:

尝试开始画图。这会确定我们需要画图的区域(在surface上)。如果这个开始调用失败了,我们检测一下原因,尝试第二次。

HRESULT MainPage::PrepareDraw(ISurfaceImageSourceNative* sisn, const RECT& updateRect, IDXGISurface** surface, POINT* offset){  HRESULT hr;  hr = sisn->BeginDraw(updateRect, surface, offset);  if ((hr == DXGI_ERROR_DEVICE_REMOVED) || (hr == DXGI_ERROR_DEVICE_RESET))  {    CreateDevice();    // 设备有更改,并不是单纯的失败,重新创建设备,再试一次    return PrepareDraw(sisn, updateRect, surface, offset);  }  else  {    return hr;  }}

 

ComPtr<IWICBitmapSource> MainPage::LoadImageByWIC(const wchar_t* file)函数,通过WIC加载图片,既加载我们的原图像,也加载蒙版图像。

ComPtr<IWICBitmapSource> MainPage::LoadImageByWIC(const wchar_t* file){    ComPtr<IWICBitmapDecoder> decoder;  ComPtr<IWICBitmapFrameDecode> frame;  ComPtr<IWICFormatConverter> converter;  HRESULT hr;  HR(m_factory->CreateDecoderFromFilename(file, nullptr, GENERIC_READ, WICDecodeMetadataCacheOnDemand, &decoder));  HR(decoder->GetFrame(0, &frame));  HR(m_factory->CreateFormatConverter(&converter));  HR(converter->Initialize(    frame.Get(),    GUID_WICPixelFormat32bppPBGRA, // 这个预处理的BGRA,因为两个透明图层叠加时需要把RGB通道和Alpha通道相乘相加,而预处理就是预先把相乘的步骤完成了,可以增加一点效率    WICBitmapDitherTypeNone,    nullptr,    0,    WICBitmapPaletteTypeCustom));  return converter;}

 

MainPage::GetMask函数把黑白色的图片处理成用alpha通道表示透明度的bitmap。因为只有黑白色的话,颜色是通过RGB通道确定的,alpha通道一直是1.0。而direct2D提供的API呢,却是使用的alpha通道来进行蒙版应用。这样看似合理一些,但我们生成一张利用alpha通道来表现透明度的蒙版图片,肯定是要比我们用单纯的黑白色来表现蒙版要麻烦一些的。

ComPtr<IWICBitmapSource> MainPage::GetMask(IWICBitmapSource* src){  uint32_t width, height;  src->GetSize(&width, &height);  size_t len = width * 4 * height;  unique_ptr<byte[]> pixels(new byte[len]);  src->CopyPixels(nullptr, width * 4, len, pixels.get());  for (size_t i = 0; i < width * height; i++)  {    pixels[i * 4 + 3] = (pixels[i * 4] + pixels[i * 4 + 1] + pixels[i * 4 + 2]) / 3;  }  ComPtr<IWICBitmap> bmp;  m_factory->CreateBitmapFromMemory(width, height, GUID_WICPixelFormat32bppPBGRA, width * 4, len, pixels.get(), &bmp);  return bmp;}

 

用Direct2D的好处

图形应用(包括图像处理,地图),游戏,这些特殊的应用需要一个强悍的图形技术来支撑它们的运作和体验,而Direct2D无疑为我们提供了这样的可能,让我们能在XAML之中,发挥图形技术的强大威力。

 

扩展

对于SurfaceImageSource,除了转换成ISurfaceImageSourceNative接口外,还能转换成ISurfaceImageSourceNativeWithD2D接口,区别就在于withD2D的这一个,可以在后台线程上画图,只要在UI线程上刷新就可以了。

SurfaceImageSource还有一个子类,VirtualSurfaceImageSource,它主要是起虚拟化的作用,用于图像区域比可视区域大的情况,比如地图。

附录

[1] 关于Direct2D:

https://msdn.microsoft.com/zh-cn/library/windows/desktop/dd370987(v=vs.85).aspx

[2] DirectX 和 XAML 互操作

https://msdn.microsoft.com/zh-cn/library/windows/apps/hh825871.aspx

[3] SurfaceImageSource类:

https://msdn.microsoft.com/zh-cn/library/windows/apps/windows.ui.xaml.media.imaging.surfaceimagesource.aspx

[4] ISurfaceImageSourceNative接口:

 https://msdn.microsoft.com/zh-cn/library/windows/apps/hh848322.aspx

 

完整代码

MainPage.xaml.h

//// MainPage.xaml.h// Declaration of the MainPage class.//#pragma once#include "MainPage.g.h"namespace App2{/// <summary>/// An empty page that can be used on its own or navigated to within a Frame./// </summary>public ref class MainPage sealed{public:  MainPage();  void OnNavigatedTo(Windows::UI::Xaml::Navigation::NavigationEventArgs^ e) override;private:  void OnButtonClick(Platform::Object^ sender, Windows::UI::Xaml::RoutedEventArgs^ e);  void CreateDevice();  Microsoft::WRL::ComPtr<IWICBitmapSource> LoadImageByWIC(const wchar_t* file);  Microsoft::WRL::ComPtr<IWICBitmapSource> GetMask(IWICBitmapSource* src);  void Draw(ISurfaceImageSourceNative* sisn, const wchar_t* mask);  HRESULT PrepareDraw(ISurfaceImageSourceNative* sisn, const RECT& updateRect, IDXGISurface** surface, POINT* offset);  Microsoft::WRL::ComPtr<IWICImagingFactory> m_factory;  Microsoft::WRL::ComPtr<IDXGIDevice> m_dxgiDevice;  Microsoft::WRL::ComPtr<ID2D1DeviceContext> m_d2dDeviceContext;  Microsoft::WRL::ComPtr<IWICBitmapSource> m_img;};}

View Code

MainPage.xaml.cpp

//// MainPage.xaml.cpp// Implementation of the MainPage class.//#include "pch.h"#include "MainPage.xaml.h"using namespace App2;using namespace Platform;using namespace Windows::Foundation;using namespace Windows::Foundation::Collections;using namespace Windows::UI::Xaml;using namespace Windows::UI::Xaml::Controls;using namespace Windows::UI::Xaml::Controls::Primitives;using namespace Windows::UI::Xaml::Data;using namespace Windows::UI::Xaml::Input;using namespace Windows::UI::Xaml::Media;using namespace Windows::UI::Xaml::Media::Imaging;using namespace Windows::UI::Xaml::Navigation;using namespace Microsoft::WRL;using namespace std;#define HR(exp) hr = exp; assert(SUCCEEDED(hr))// The Blank Page item template is documented at http://go.microsoft.com/fwlink/?LinkId=402352&clcid=0x409MainPage::MainPage(){  InitializeComponent();}void MainPage::OnNavigatedTo(Windows::UI::Xaml::Navigation::NavigationEventArgs^ e){  for (UIElement^ uiElem : btns->Children)  {    auto btn = safe_cast<Button^>(uiElem);    btn->Click += ref new RoutedEventHandler(this, &MainPage::OnButtonClick);  }  CreateDevice();  HRESULT hr;  HR(CoCreateInstance(CLSID_WICImagingFactory, nullptr, CLSCTX_INPROC_SERVER, IID_PPV_ARGS(&m_factory)));  m_img = LoadImageByWIC(L"Assets/img.png");}void MainPage::CreateDevice(){  static D3D_FEATURE_LEVEL featureLevels[] =  {    D3D_FEATURE_LEVEL_11_1,    D3D_FEATURE_LEVEL_11_0,    D3D_FEATURE_LEVEL_10_1,    D3D_FEATURE_LEVEL_10_0,    D3D_FEATURE_LEVEL_9_3,    D3D_FEATURE_LEVEL_9_2,    D3D_FEATURE_LEVEL_9_1  };  HRESULT hr;  ComPtr<ID3D11Device> d3dDevice;  ComPtr<ID2D1Device> d2dDevice;  HR(D3D11CreateDevice(nullptr,    D3D_DRIVER_TYPE_HARDWARE,    0,    D3D11_CREATE_DEVICE_BGRA_SUPPORT,    featureLevels,    extent<decltype(featureLevels)>::value,    D3D11_SDK_VERSION,    &d3dDevice,    nullptr,    nullptr));  HR(d3dDevice.As(&m_dxgiDevice));  HR(D2D1CreateDevice(m_dxgiDevice.Get(), nullptr, &d2dDevice));  HR(d2dDevice->CreateDeviceContext(D2D1_DEVICE_CONTEXT_OPTIONS_NONE, &m_d2dDeviceContext));}ComPtr<IWICBitmapSource> MainPage::LoadImageByWIC(const wchar_t* file){    ComPtr<IWICBitmapDecoder> decoder;  ComPtr<IWICBitmapFrameDecode> frame;  ComPtr<IWICFormatConverter> converter;  HRESULT hr;  HR(m_factory->CreateDecoderFromFilename(file, nullptr, GENERIC_READ, WICDecodeMetadataCacheOnDemand, &decoder));  HR(decoder->GetFrame(0, &frame));  HR(m_factory->CreateFormatConverter(&converter));  HR(converter->Initialize(    frame.Get(),    GUID_WICPixelFormat32bppPBGRA, // Pre-multipled BGRA    WICBitmapDitherTypeNone,    nullptr,    0,    WICBitmapPaletteTypeCustom));  return converter;}ComPtr<IWICBitmapSource> MainPage::GetMask(IWICBitmapSource* src){  uint32_t width, height;  src->GetSize(&width, &height);  size_t len = width * 4 * height;  unique_ptr<byte[]> pixels(new byte[len]);  src->CopyPixels(nullptr, width * 4, len, pixels.get());  for (size_t i = 0; i < width * height; i++)  {    // BGRA. The average of RGB channels is used as Alpha channel.    pixels[i * 4 + 3] = (pixels[i * 4] + pixels[i * 4 + 1] + pixels[i * 4 + 2]) / 3;  }  ComPtr<IWICBitmap> bmp;  m_factory->CreateBitmapFromMemory(width, height, GUID_WICPixelFormat32bppPBGRA, width * 4, len, pixels.get(), &bmp);  return bmp;}void MainPage::OnButtonClick(Object^ sender, RoutedEventArgs^ e){  HRESULT hr;  auto btn = safe_cast<Button^>(sender);  auto maskPath = btn->Tag->ToString();  SurfaceImageSource^ sis = ref new SurfaceImageSource(400, 400);  ComPtr<ISurfaceImageSourceNative> sisn;  HR(reinterpret_cast<IInspectable*>(sis)->QueryInterface(IID_PPV_ARGS(&sisn)));  HR(sisn->SetDevice(m_dxgiDevice.Get())); // set device as DXGI device.  // Note this  auto brush = ref new ImageBrush();  brush->ImageSource = sis;  canvas->Fill = brush;  Draw(sisn.Get(), maskPath->Data());}void MainPage::Draw(ISurfaceImageSourceNative* sisn, const wchar_t* mask){  HRESULT hr;  ComPtr<IDXGISurface> surface;  RECT rect = { 0, 0, 400, 400 };  POINT renderTargetOffset; // view port offset in surface.  HR(PrepareDraw(sisn, rect, &surface, &renderTargetOffset));  ComPtr<IWICBitmapSource> maskSrc = GetMask(LoadImageByWIC(mask).Get());  ComPtr<ID2D1Bitmap> maskBmp;  ComPtr<ID2D1Bitmap> imgBmp;  ComPtr<ID2D1BitmapBrush> imgBrush;  ComPtr<ID2D1Bitmap1> tgrBmp; // Note ID2D1Bitmap1  HR(m_d2dDeviceContext->CreateBitmapFromWicBitmap(maskSrc.Get(), &maskBmp));  HR(m_d2dDeviceContext->CreateBitmapFromWicBitmap(m_img.Get(), &imgBmp));  HR(m_d2dDeviceContext->CreateBitmapBrush(imgBmp.Get(), &imgBrush));  HR(m_d2dDeviceContext->CreateBitmapFromDxgiSurface(surface.Get(), nullptr, &tgrBmp));  m_d2dDeviceContext->SetTarget(tgrBmp.Get());  m_d2dDeviceContext->BeginDraw();  m_d2dDeviceContext->SetTransform(D2D1::Matrix3x2F::Translation(renderTargetOffset.x, renderTargetOffset.y));  m_d2dDeviceContext->Clear({0, 0, 1, 1}); // Clear with blue color.    m_d2dDeviceContext->SetAntialiasMode(D2D1_ANTIALIAS_MODE_ALIASED); // Must set antialias mode.  m_d2dDeviceContext->FillOpacityMask(maskBmp.Get(), imgBrush.Get());  HR(m_d2dDeviceContext->EndDraw());  m_d2dDeviceContext->SetTarget(nullptr);  HR(sisn->EndDraw());}HRESULT MainPage::PrepareDraw(ISurfaceImageSourceNative* sisn, const RECT& updateRect, IDXGISurface** surface, POINT* offset){  HRESULT hr;  hr = sisn->BeginDraw(updateRect, surface, offset);  if ((hr == DXGI_ERROR_DEVICE_REMOVED) || (hr == DXGI_ERROR_DEVICE_RESET))  {    CreateDevice();    // Device changed, try again.    return PrepareDraw(sisn, updateRect, surface, offset);  }  else  {    return hr;  }}

View Code

MainPage.xaml见正文。