Encapsulating the GDI+ drawing methods

windows GDI+ 绘图的简单封装

Brief: A simple package of GDI+ drawing methods makes the drawing in mfc much easier.

由于用mfc经常需要在界面上进行一些绘制输出，所以用windows GDI比较多，但是用windowsGDI 绘图比较麻烦，刚开始学的时候还经常弄不清一堆DC, Object, HANDLE到底是干啥的。后来就琢磨清楚了，但为了用起来更方便，就弄个类，这样画什么就直接调对应的函数和常用的控制参数，比如大小位置颜色，而不需要自己去操控上下文、绘制画笔画刷等等麻烦事，而且一个函数完成一个简单图形的绘制，后面又学了gdi+，就重写了部分函数实现，用了更简单的方式完成。

为了避免闪烁，这里用了双缓存的原理，其实就是相当于在内存里开辟空间画完后在显示在屏幕上。至于闪烁的缘由，在我的另一篇博文里面有浅浅的探究：http://www.straka.cn/blog/flickering-in-mfc/

这里也不得不指明这么做是有损效率的，因为期间会重复创建和销毁画笔画刷等对象。但对于多数应用场景，这个损失是可以接受的。

要使用GDI+（Graphics device interface），要做些铺垫工作，

	ULONG_PTR m_gdiplusToken;

BOOL CGDIDemoApp::InitInstance()
{
...
	CWinApp::InitInstance();

	Gdiplus::GdiplusStartupInput gdiplusStartupInput;
	Gdiplus::GdiplusStartup(&m_gdiplusToken, &gdiplusStartupInput, NULL);
...
}

int CGDIDemoApp::ExitInstance()
{
	// TODO: 在此添加专用代码和/或调用基类
	Gdiplus::GdiplusShutdown(m_gdiplusToken);
	return CWinApp::ExitInstance();
}

ULONG_PTR m_gdiplusToken;

BOOL CGDIDemoApp::InitInstance()

{

...

CWinApp::InitInstance();

Gdiplus::GdiplusStartupInput gdiplusStartupInput;

Gdiplus::GdiplusStartup(&m_gdiplusToken, &gdiplusStartupInput, NULL);

...

}

int CGDIDemoApp::ExitInstance()

{

// TODO: 在此添加专用代码和/或调用基类

Gdiplus::GdiplusShutdown(m_gdiplusToken);

return CWinApp::ExitInstance();

}

一般为了方便在应用程序的实例初始化阶段就可以把gdiplus一起初始化了，然后实现ExitInstance虚函数，在其中释放使用gdiplus所占的资源。

封装的类：

class CDrawMethod
{
	HWND m_dlgHWND; //the handle of dialog window
	CDC *m_pDC;     //the device context of dialog
	CDC m_dcMem;    //the memory dc, to contain all the drawing than flush onto screen
	CBitmap m_bmpMem;  //bitmap bind to memory dc--m_dcMem 
	Gdiplus::Graphics* m_pGraph; //point to the object of Gdiplus
	
	CDrawMethod(HWND hwnd, CDC *pDC);
	~CDrawMethod();
	//call this func to init the member before any draw method
	int BeginDraw();
	//after all operate has been executed(drawn on memory DC), call this to draw on screen
	void DrawOnScreen();
	//call this func after all operate has done, free or release the resources, in case of memory leak
	int EndDraw();
	
	//save picture in memory DC to path as jpg file
	int SaveMemDCAsJPG(char* strPath);
	int SaveMemDCAsBMP(char* strPath);

	//return the memory bitmap member 
	CBitmap *GetMemBitmap();
	//return the memory DC member
	CDC *GetMemDC();
public:
	CRect m_rtClient;
};

class CDrawMethod

{

HWND m_dlgHWND; //the handle of dialog window

CDC *m_pDC; //the device context of dialog

CDC m_dcMem; //the memory dc, to contain all the drawing than flush onto screen

CBitmap m_bmpMem; //bitmap bind to memory dc--m_dcMem

Gdiplus::Graphics* m_pGraph; //point to the object of Gdiplus

CDrawMethod(HWND hwnd, CDC *pDC);

~CDrawMethod();

//call this func to init the member before any draw method

int BeginDraw();

//after all operate has been executed(drawn on memory DC), call this to draw on screen

void DrawOnScreen();

//call this func after all operate has done, free or release the resources, in case of memory leak

int EndDraw();

//save picture in memory DC to path as jpg file

int SaveMemDCAsJPG(char* strPath);

int SaveMemDCAsBMP(char* strPath);

//return the memory bitmap member

CBitmap *GetMemBitmap();

//return the memory DC member

CDC *GetMemDC();

public:

CRect m_rtClient;

};

主要的成员和函数都在上述代码中列出，使用的话每次新建类实例，传入对话框句柄HANDLE和设备上下文DC，然后调用BeginDraw()初始化，等全部函数执行完毕，再调用DrawOnScreen()画到屏幕上，最后EndDraw()释放资源。如果需要更进一步的操作可以用GetMemBitmap() 和 GetMemDC()方法取得内存位图和画布进一步操作。但是注意这里的指针是指向成员的，用完不可释放，类内部管理。如果画完不需要显示在显示器上也可以用SaveMemDCAsJPG 和 SaveMemDCAsBMP 函数输出到文件。

而具体承担绘图任务的函数是自定义可以添加的：

        //putout the text follow the params onto the dc
	TEXTMETRIC PutOutTextA(char* lpsz, int X, int Y, unsigned long lColor, int nFontHeight, int nFontWidth = FW_NORMAL, EShadowType eShadow = NONE, unsigned long lShadowColor = 0, LPCWSTR lpFont = TEXT("微软雅黑"));
	TEXTMETRIC PutOutTextW(char* lpsz, int X, int Y, unsigned long lColor, int nFontHeight, int nFontWidth = FW_NORMAL, EShadowType eShadow = NONE, unsigned long lShadowColor = 0, LPCWSTR lpFont = TEXT("微软雅黑"));
	
	
	//draw rectangle frame
	void DrawRectFrame(CRect rect,int width, unsigned long lColor,byte alpha=255);
	//draw shadow of rectangle 
	//@param coeff: control the color gradiant rate
	void DrawRectShadow(CRect rect, unsigned long lColor, byte alpha, int width, float coeff=0.8);
	//fill inside of  rectangle 
	void FillRect(CRect rect, unsigned long lColor, byte alpha);
	
	void DrawEllipseFrame(CRect rect, int width, unsigned long lColor, byte alpha=255);
	void DrawEllipseShadow(CRect rect, unsigned long lColor, byte alpha, int width, float coeff=0.8);
	void FillEllipse(CRect rect, unsigned long lColor, byte alpha);
	
	void DrawPolygonFrame(Gdiplus::Point* arrPoints, int ctn, int width, unsigned long lColor, byte alpha=255);
	void FillPolygon(Gdiplus::Point* arrPoints, int ctn, unsigned long lColor, byte alpha);
	//draw round corner rectangle
	void DrawRoundRect(CRect rect, float arcSize, float lineWidth, unsigned long lColor, byte alpha, bool fillPath = false, unsigned long lColorFill = 0, byte alphaFill = 0);
	void DrawRoundRect(float x, float y, float Width, float Height, float arcSize, float lineWidth, unsigned long lColor, byte alpha, bool fillPath = false, unsigned long lColorFill = 0, byte alphaFill = 0);
	
	//method to draw cubic of area located by points array
	void FillCubicSurface(Gdiplus::Point* arrPoints, int ctn, unsigned long lColor, byte alpha = 155,unsigned long frameColor = 0);

	//draw image on path by method 1 to location by rect
	bool DrawImage(char* pStr, CRect rect);
	//draw png picture at path input to location by rect
	void DrawPNG(WCHAR* strPath, CRect rect);

//putout the text follow the params onto the dc

TEXTMETRIC PutOutTextA(char* lpsz, int X, int Y, unsigned long lColor, int nFontHeight, int nFontWidth = FW_NORMAL, EShadowType eShadow = NONE, unsigned long lShadowColor = 0, LPCWSTR lpFont = TEXT("微软雅黑"));

TEXTMETRIC PutOutTextW(char* lpsz, int X, int Y, unsigned long lColor, int nFontHeight, int nFontWidth = FW_NORMAL, EShadowType eShadow = NONE, unsigned long lShadowColor = 0, LPCWSTR lpFont = TEXT("微软雅黑"));

//draw rectangle frame

void DrawRectFrame(CRect rect,int width, unsigned long lColor,byte alpha=255);

//draw shadow of rectangle

//@param coeff: control the color gradiant rate

void DrawRectShadow(CRect rect, unsigned long lColor, byte alpha, int width, float coeff=0.8);

//fill inside of rectangle

void FillRect(CRect rect, unsigned long lColor, byte alpha);

void DrawEllipseFrame(CRect rect, int width, unsigned long lColor, byte alpha=255);

void DrawEllipseShadow(CRect rect, unsigned long lColor, byte alpha, int width, float coeff=0.8);

void FillEllipse(CRect rect, unsigned long lColor, byte alpha);

void DrawPolygonFrame(Gdiplus::Point* arrPoints, int ctn, int width, unsigned long lColor, byte alpha=255);

void FillPolygon(Gdiplus::Point* arrPoints, int ctn, unsigned long lColor, byte alpha);

//draw round corner rectangle

void DrawRoundRect(CRect rect, float arcSize, float lineWidth, unsigned long lColor, byte alpha, bool fillPath = false, unsigned long lColorFill = 0, byte alphaFill = 0);

void DrawRoundRect(float x, float y, float Width, float Height, float arcSize, float lineWidth, unsigned long lColor, byte alpha, bool fillPath = false, unsigned long lColorFill = 0, byte alphaFill = 0);

//method to draw cubic of area located by points array

void FillCubicSurface(Gdiplus::Point* arrPoints, int ctn, unsigned long lColor, byte alpha = 155,unsigned long frameColor = 0);

//draw image on path by method 1 to location by rect

bool DrawImage(char* pStr, CRect rect);

//draw png picture at path input to location by rect

void DrawPNG(WCHAR* strPath, CRect rect);

我就把常用的一些添加了进来，画矩形、椭圆形、多边形框、及填充矩形、椭圆形、多边形内部、画矩形、椭圆形阴影，画圆角矩形、画立方体，绘制图片,以及输出文字。

其中画矩形阴影实现就是画了尺寸稍大的多个矩形，这种比较简单，当然也有别的处理方法，根据大家需要另外添加函数即可。

使用示例：

在对话框OnPaint函数中添加代码：

        if (IsIconic())
	{
		...
        }
	else
	{
		//CDialogEx::OnPaint();
		CPaintDC dc(this); // 用于绘制的设备上下文
		CDrawMethod drawMethod(m_hWnd,&dc);
		drawMethod.BeginDraw();
		...//draw objects here
		drawMethod.DrawOnScreen();

		drawMethod.EndDraw();
	}

if (IsIconic())

{

...

}

else

{

//CDialogEx::OnPaint();

CPaintDC dc(this); // 用于绘制的设备上下文

CDrawMethod drawMethod(m_hWnd,&dc);

drawMethod.BeginDraw();

...//draw objects here

drawMethod.DrawOnScreen();

drawMethod.EndDraw();

}

在第11行处添加画图代码，比如：

drawMethod.DrawRectFrame(rect1,1,RGB(0,255,0),150);
drawMethod.DrawRectShadow(rect1,RGB(200,255,255),200,5);
drawMethod.FillRect(rect1,RGB(255,0,0),150);

drawMethod.DrawEllipseFrame(rect2,1,RGB(100,20,155),200);
drawMethod.DrawEllipseShadow(rect2,RGB(0,255,255),200,5,0.7);
drawMethod.FillEllipse(rect2,RGB(255,255,0),190);

Gdiplus::Point pts[8];
pts[0].X = 170; pts[0].Y = 250;
pts[1].X = 280; pts[1].Y = pts[0].Y;
pts[2].X = 400; pts[2].Y = 100;
pts[3].X = 330; pts[3].Y = pts[2].Y;
pts[4].X = pts[0].X; pts[4].Y = 210;
pts[5].X = pts[1].X; pts[5].Y = pts[4].Y;
pts[6].X = pts[2].X; pts[6].Y = 75;
pts[7].X = pts[3].X; pts[7].Y = pts[6].Y;
drawMethod.FillCubicSurface(pts,8,RGB(0,200,50),200,RGB(0,255,0));

drawMethod.DrawRectFrame(rect1,1,RGB(0,255,0),150);

drawMethod.DrawRectShadow(rect1,RGB(200,255,255),200,5);

drawMethod.FillRect(rect1,RGB(255,0,0),150);

drawMethod.DrawEllipseFrame(rect2,1,RGB(100,20,155),200);

drawMethod.DrawEllipseShadow(rect2,RGB(0,255,255),200,5,0.7);

drawMethod.FillEllipse(rect2,RGB(255,255,0),190);

Gdiplus::Point pts[8];

pts[0].X = 170; pts[0].Y = 250;

pts[1].X = 280; pts[1].Y = pts[0].Y;

pts[2].X = 400; pts[2].Y = 100;

pts[3].X = 330; pts[3].Y = pts[2].Y;

pts[4].X = pts[0].X; pts[4].Y = 210;

pts[5].X = pts[1].X; pts[5].Y = pts[4].Y;

pts[6].X = pts[2].X; pts[6].Y = 75;

pts[7].X = pts[3].X; pts[7].Y = pts[6].Y;

drawMethod.FillCubicSurface(pts,8,RGB(0,200,50),200,RGB(0,255,0));

上述代码绘图效果：

代码下载：

GDIDemo

https://github.com/atp798/BlogStraka/

Welcom !

Encapsulating the GDI+ drawing methods

windows GDI+ 绘图的简单封装

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windows GDI+ 绘图的简单封装

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