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！