Direct2D 几何图形绘制基础

之前说过，D2D主要为了绘制有三种类型的数据：几何图形，图片，文字。这几种对象也叫做资源，资源就是要D2D流水线中要被加工的对象。

几何图形包括：

 

• 简单几何图形
  • 直线，DrawLine，由起点和终点构成，点用结构体：D2D1_POINT_2F描述。
  • 矩形，ID2D1RectangleGeometry，DrawRectangle，由距四条边的距离表示，用结构体：D2D1_RECT_F描述。
  • 圆角矩形，ID2D1RoundedRectangleGeometry ，DrawRoundedRectangle，同矩形，用结构体：D2D1_ROUNDED_RECT描述，另外还要加入圆角参数。
  • 椭圆，包括圆，ID2D1EllipseGeometry ，DrawEllipse，用结构体：D2D1_ELLIPSE 描述。
• 路径，ID2D1PathGeometry 
• 组合图形，
  • 几何图形组合，ID2D1GeometryGroup 
  • 变幻几何图形，ID2D1TransformedGeometry 

准备绘制：

在开始绘制之前，至少要准备好3样东西：

• D2D工厂对象，ID2D1Factory接口。用于创建绘制目标，用方法CreateHwndRenderTarget。
  
• 渲染窗口，ID2D1HwndRenderTarget接口。如果是Win32程序就是默认的HWND窗口，如果是商店应用则是一个绘制表面的控件。
  渲染窗口同时还负责着绘制几何图形，文字和图片。
  
• 画刷，ID2D1SolidColorBrush接口。绘制几何图形时用于指定图形的样式。
• 绘制区域，如果是win32程序还需要指定渲染窗口中要绘制的区域。

首先要引入头文件和命名空间：

#include "windows.h"

#include "D2D1.h"



using namespace D2D1;

别忘了加要链接的Lib，要input的lib如下：

d2d1.lib;

dxgi.lib;

dwrite.lib;

dxguid.lib;

windowscodecs.lib;

声明以上4个对象的代码如下：

	// Direct2D factory

	ID2D1Factory* pD2DFactory; 

	// Render target

	ID2D1HwndRenderTarget* pRenderTarget;

	// A black brush, reflect the line color

	ID2D1SolidColorBrush* pBlackBrush; 

	// Render area

	RECT rc ; 

初始化这些值的代码如下：

	//create d2d factory

	hr =  D2D1CreateFactory(D2D1_FACTORY_TYPE_SINGLE_THREADED, &pD2DFactory) ;

	//create render target (hwnd window)

	GetClientRect(hWnd, &rc);

	hr = pD2DFactory->CreateHwndRenderTarget( RenderTargetProperties(), HwndRenderTargetProperties(hWnd, SizeU(rc.right - rc.left, rc.bottom - rc.top)), &pRenderTarget);

	//create brush

	hr = pRenderTarget->CreateSolidColorBrush(ColorF(ColorF::Blue), &pBlackBrush);

然后就可以开始绘制了。笔者使用的程序是win32应用程序，绘制的代码都必须写在WndProc回调函数的case WM_PAINT:之后，并且要将所有绘制代码都包含在pRenderTarget->BeginDraw();和pRenderTarget->EndDraw();之间。例如：

	pRenderTarget->BeginDraw();



	//clear screen

	pRenderTarget->Clear(D2D1::ColorF(D2D1::ColorF::White));



	//draw line with 2 points

	D2D1_POINT_2F ptStart = Point2F(0,0);

	D2D1_POINT_2F ptEnd = Point2F(100,100);

	pRenderTarget->DrawLine(ptStart,ptEnd,pBlackBrush);

	

	//draw rectangle

	D2D1_RECT_F rect  = RectF(rc.left + 100.0f, rc.top + 100.0f, rc.right - 100.0f, rc.bottom - 100.0f);

	pRenderTarget->DrawRectangle(rect, pBlackBrush);



	//draw round rect

	D2D1_ROUNDED_RECT roundrect  = RoundedRect(RectF(rc.left + 100.0f, rc.top + 100.0f, rc.right - 100.0f, rc.bottom - 100.0f), 30.0f, 50.0f);

	pRenderTarget->DrawRoundedRectangle(roundrect, pBlackBrush, 1.0f);



	pRenderTarget->EndDraw();

WM_PAINT是在窗口需要重绘时由系统调用的，所以我们不用主动地去调用它，它们不断地刷新的。
当然了，把代码都积压在WM_PAINT之后也太SB了，最好自己封装一个类，如下：

头文件如下：

#pragma once



#include "stdafx.h"

#include "windows.h"

#include "D2D1.h"



using namespace D2D1;



class D2DRender

{

public:

	D2DRender(void);

	~D2DRender(void);

	

	HRESULT CreateDeviceIndependentResources();

	HRESULT CreateDeviceResources(HWND hWnd);

	void OnRender();

	void DiscardDeviceResources();

	void OnResize(UINT width, UINT height);



private:

	// Direct2D factory

	ID2D1Factory* pD2DFactory; 

	// Render target

	ID2D1HwndRenderTarget* pRenderTarget;

	// A black brush, reflect the line color

	ID2D1SolidColorBrush* pBlackBrush; 

	// Render area

	RECT rc ; 

	//result

	HRESULT hr;

};

实现如下：

#include "stdafx.h"

#include "D2DRender.h"



D2DRender::D2DRender()

{

	// Direct2D factory

	pD2DFactory = NULL; 

	// Render target

	pRenderTarget = NULL;

	// A black brush, reflect the line color

	pBlackBrush = NULL; 	

}



D2DRender::~D2DRender()

{

	pD2DFactory->Release();

	pRenderTarget->Release();

	pBlackBrush->Release();



}



void D2DRender::DiscardDeviceResources()

{

	pD2DFactory->Release();

	pRenderTarget->Release();

	pBlackBrush->Release();

}





void D2DRender::OnResize(UINT width, UINT height)

{

	if(pRenderTarget)

	{

		pRenderTarget->Resize(SizeU(width,height));

	}

}



HRESULT D2DRender::CreateDeviceIndependentResources()

{

	//create d2d factory

	hr =  D2D1CreateFactory(D2D1_FACTORY_TYPE_SINGLE_THREADED, &pD2DFactory) ;



	return hr;

}



HRESULT D2DRender::CreateDeviceResources(HWND hWnd)

{

	//create render target (hwnd window)

	GetClientRect(hWnd, &rc);

	hr = pD2DFactory->CreateHwndRenderTarget( RenderTargetProperties(), HwndRenderTargetProperties(hWnd, SizeU(rc.right - rc.left, rc.bottom - rc.top)), &pRenderTarget);



	//create brush

	hr = pRenderTarget->CreateSolidColorBrush(ColorF(ColorF::Blue), &pBlackBrush);



	return hr;

}



void D2DRender::OnRender()

{

	pRenderTarget->BeginDraw();



	//clear screen

	pRenderTarget->Clear(D2D1::ColorF(D2D1::ColorF::White));



	//draw line with 2 points

	D2D1_POINT_2F ptStart = Point2F(0,0);

	D2D1_POINT_2F ptEnd = Point2F(100,100);

	pRenderTarget->DrawLine(ptStart,ptEnd,pBlackBrush);

	

	//draw rectangle

	D2D1_RECT_F rect  = RectF(rc.left + 100.0f, rc.top + 100.0f, rc.right - 100.0f, rc.bottom - 100.0f);

	pRenderTarget->DrawRectangle(rect, pBlackBrush);



	//draw round rect

	D2D1_ROUNDED_RECT roundrect  = RoundedRect(RectF(rc.left + 100.0f, rc.top + 100.0f, rc.right - 100.0f, rc.bottom - 100.0f), 30.0f, 50.0f);

	pRenderTarget->DrawRoundedRectangle(roundrect, pBlackBrush, 1.0f);



	pRenderTarget->EndDraw();

}

然后在WM_PANIT里调用，默认生成的gdi绘制用到的hdc相关代码可以删掉。

	case WM_PAINT:

		//hdc = BeginPaint(hWnd, &ps);

		D2DRender pRender;

		pRender.CreateDeviceIndependentResources();

		pRender.CreateDeviceResources(hWnd);

		pRender.OnRender();

		//EndPaint(hWnd, &ps);

		break;

还是比较简单。