C++ GDI+ DrawString 保存字符串文字为透明图片

实现通过GDI+将输入的字符串保存为背景透明的图片的示例代码

【1】头文件

#ifndef  _AFXSTD_EF4A7E9D_ECEF_4D13_B0AD_ADEB38D1E347_INCLUDE_H_
#define  _AFXSTD_EF4A7E9D_ECEF_4D13_B0AD_ADEB38D1E347_INCLUDE_H_


#if _MSC_VER > 1000
#pragma  once
#endif


#include <string>
using namespace std;

#include <gdiplus.h>

//==================================CTextToImage==================================
/// @brief 文本转图片
///
/// 将文本字符串转成透明图片
//================================================================================
class CTextToImage
{
public:
	CTextToImage();
	CTextToImage(wstring &strText, wstring pFontName = L"宋体",  float fontSize=12, DWORD pColor=0x000000FF, int fontStyle=0);
	~CTextToImage();

public:
	void	SetString(wstring &strText);
	int		GetFontCount();
	void    GetFontNameArr(WCHAR **pFontNameArr, int numSought,  int *pNumFound);
	void    SetFontName(wstring &fontName);
	void    SetFontSize(float fontSize);
	void    SetFontColor(DWORD  color);
	void    SetFontStyle(int fontStyle);
	void    SaveToImage(HWND hWnd, wstring &strPicPath );

private:
	wstring			*m_pStrText;	//文本
	WCHAR			*m_pFontName;	//字体名称
	Gdiplus::Color  *m_pFontColor;  //文本的颜色
	float            m_FontSize;	//字号
	int				 m_FontStyle;	//字体效果规则、粗体、斜体、粗斜体、下划线、强调线
};


#endif //!_AFXSTD_EF4A7E9D_ECEF_4D13_B0AD_ADEB38D1E347_INCLUDE_H_

【2】cpp文件

#include "stdafx.h"
#include "Caption.h"

using namespace Gdiplus;

CTextToImage::CTextToImage()
{
	m_pStrText	 = new wstring;
	m_pFontColor = new Gdiplus::Color(Gdiplus::Color::Black);
	m_pFontName  = new WCHAR[32];
	wcscpy_s(m_pFontName, 32, L"宋体");
	m_FontSize   = 12;
	m_FontStyle  = Gdiplus::FontStyleRegular;
}

CTextToImage::CTextToImage( wstring &strText, wstring pFontName /*= "宋体"*/, float fontSize/*=12*/, DWORD pColor/*=0x000000FF*/, int fontStyle/*=0*/ )
{
	new(this)CTextToImage();

	*m_pStrText = strText;
	wcscpy_s(m_pFontName, 32, pFontName.c_str());
	m_FontSize  = fontSize;
	m_FontStyle = fontStyle;
	m_pFontColor->SetFromCOLORREF(pColor);
}

CTextToImage::~CTextToImage()
{
	if (NULL != m_pStrText)
	{
		delete m_pStrText;
	}

	if (NULL != m_pFontColor)
	{
		delete m_pFontColor;
	}
	if (NULL != m_pFontName)
	{
		delete []m_pFontName;
	}
}

void CTextToImage::SetString(wstring &strText )
{
	if (NULL == m_pStrText)
	{
		return;
	}

	*m_pStrText = strText;
}

bool GetEncoderClsid(const WCHAR* format, CLSID* pClsid)
{
	UINT num = 0, size = 0;

	Gdiplus::GetImageEncodersSize(&num, &size);
	if(size == 0)
		return -1;  // Failure

	Gdiplus::ImageCodecInfo* pImageCodecInfo = (Gdiplus::ImageCodecInfo*)(malloc(size));

	Gdiplus::GetImageEncoders(num, size, pImageCodecInfo);
	bool found = false;
	for (UINT ix = 0; !found && ix < num; ++ix) 
	{
		if (_wcsicmp(pImageCodecInfo[ix].MimeType, format) == 0) 
		{
			*pClsid = pImageCodecInfo[ix].Clsid;
			found = true;
			break;
		}
	}

	free(pImageCodecInfo);
	return found;
}

void CTextToImage::SaveToImage(HWND hWnd, wstring &strPicPath )
{
	if (NULL == m_pStrText || NULL == m_pFontColor)
	{
		return;
	}

	Gdiplus::FontFamily fontFamily(m_pFontName);
	Gdiplus::Font       font(&fontFamily, m_FontSize, m_FontStyle, Gdiplus::Unit::UnitPoint);
	Gdiplus::SolidBrush solidBrush(*m_pFontColor);
	Gdiplus::Graphics   graphics(hWnd);

	//Gdiplus::StringFormat stringformat;
	//stringformat.SetTrimming(StringTrimming::StringTrimmingEllipsisWord);

	//字体边沿平滑处理
	graphics.SetTextRenderingHint(Gdiplus::TextRenderingHint::TextRenderingHintAntiAlias);

	//【1】计算字符串的尺寸
	Gdiplus::RectF boundingBox(0, 0, 0, 0);
	graphics.MeasureString(m_pStrText->c_str(), -1, &font, Gdiplus::PointF(0, 0), &boundingBox);

	//【2】创建bitMap	
	Gdiplus::SizeF  size;
	boundingBox.GetSize(&size);
	Gdiplus::Bitmap bitmap((int)size.Width, (int)size.Height, PixelFormat32bppARGB);
	Gdiplus::Graphics g(&bitmap);

	//【3】绘制文本
	g.DrawString(m_pStrText->c_str(), -1, &font, Gdiplus::PointF(0, 0), &solidBrush);
	
	CLSID   clsID			 = GUID_NULL;
	wchar_t ext[_MAX_EXT]    = {0};
	wchar_t format[_MAX_EXT] = {L"image/"};

	_wsplitpath_s(strPicPath.c_str(), NULL, 0, NULL, 0, NULL, 0, ext, _MAX_EXT);
	wcscat_s(format, _MAX_EXT, ext + 1);
	if (GetEncoderClsid(format, &clsID))
	{
		bitmap.Save(strPicPath.c_str(), &clsID, NULL);
	}	
}

void CTextToImage::SetFontColor( DWORD color )
{
	m_pFontColor->SetFromCOLORREF(color);
}

void CTextToImage::GetFontNameArr(WCHAR **pFontNameArr, int numSought, int *pNumFound)
{
	if (NULL == pFontNameArr || numSought < 1)
		return;	
	
	//获取字体名称列表
	FontFamily *pFontFamily = new FontFamily[numSought];

	InstalledFontCollection installedFontCollection;  
	installedFontCollection.GetFamilies(numSought, pFontFamily, pNumFound);  
	
	for(int j=0; j<*pNumFound; j++)
	{  
		pFontFamily[j].GetFamilyName(pFontNameArr[j]); 	
	}  
	
	delete[] pFontFamily;  
}

int CTextToImage::GetFontCount()
{
	InstalledFontCollection installedFontCollection;  
	return ( installedFontCollection.GetFamilyCount() );  
}

void CTextToImage::SetFontName( wstring &fontName )
{
	wcscpy_s(m_pFontName, 32, fontName.c_str());	
}

void CTextToImage::SetFontSize( float fontSize )
{
	m_FontSize = fontSize;
}

void CTextToImage::SetFontStyle( int fontStyle )
{
	m_FontStyle = fontStyle;
}

【3】测试代码

CTextToImage  txtImage(wstring(L"dafsdfasd"));
	txtImage.SaveToImage(m_picCtrl, wstring(L"D:\\filterTest\\txtTojpg.png"));

说明：保存为png格式的图片才可以带透明通道！