首先是抓圖服務：

ICaptureHelper.h

#pragma once

#include <windows.h>
#include <string>
using std::string;

class ICaptureHelper
{
public:
  virtual ~ICaptureHelper() {}
  virtual bool Init(const string& windowName) = 0;
  virtual bool Init(HWND hwnd) = 0;
  virtual void Cleanup() = 0;
  virtual bool RefreshWindow() = 0;
  virtual bool ChangeWindowHandle(const string& windowName) = 0;
  virtual bool ChangeWindowHandle(HWND hwnd) = 0;
  virtual bool Capture() = 0;

  virtual const RECT& GetWindowRect() const = 0;
  virtual const RECT& GetClientRect() const = 0;
  virtual int GetBitmapDataSize() const = 0;
  virtual HBITMAP GetBitmap() const = 0;
  virtual void* GetBitmapAddress() const = 0;
};

CaptureService.h

#pragma once

#include "ICaptureHelper.h"
#include <map>
using std::map;

class CaptureService
{
public:
  CaptureService() = default;
  static CaptureService& GetInstance();

  enum CaptureType
  {
    //使用CreateDIBSection抓圖，速度快，但是無法抓取D3D等渲染的視窗
    CreateDibSection = 0,//使用PrintWindow抓圖，速度慢(16ms左右)，但是可以抓取D3D等渲染的視窗
    PrintWindow
  };

  bool RegisterCapture(string name,string windowName,CaptureType type = CreateDibSection); //註冊抓圖服務
  bool RegisterCapture(string name,HWND hwnd,CaptureType type = CreateDibSection); //註冊抓圖服務
  void UnRegisterCapture(string name); //登出抓圖服務
  bool IsRegister(string name); //獲取是否已註冊抓圖服務

  bool RefreshWindow(string name); //重新整理視窗
  bool ChangeWindowHandle(string name,string windowName); //修改視窗控制代碼
  bool ChangeWindowHandle(string name,HWND hwnd); //修改視窗控制代碼
  bool Capture(string name); //抓圖

  bool GetWindowRect(string name,RECT& winRect); //獲取視窗尺寸
  bool GetClientRect(string name,RECT& clientRect); //獲取視窗客戶區尺寸
  bool GetBitmapDataSize(string name,int& bmpDataSize); //獲取抓圖資料大小
  bool GetBitmap(string name,HBITMAP& bitmap); //獲取視窗點陣圖
  bool GetBitmapAddress(string name,void** bitsPtr); //獲取視窗點陣圖地址

  void Cleanup(); //清理所有抓圖服務

private:
  ~CaptureService();

private:
  map<string,ICaptureHelper*> captureHelpers_;
};

其次是抓圖程式碼封裝：

AbsCaptureHelper.h

#pragma once

#include "ICaptureHelper.h"

class AbsCaptureHelper : public ICaptureHelper
{
public:
  AbsCaptureHelper();
  virtual ~AbsCaptureHelper();

  bool Init(const string& windowName) override;
  bool Init(HWND hwnd) override;
  void Cleanup() override;
  bool RefreshWindow() override;
  bool ChangeWindowHandle(const string& windowName) override;
  bool ChangeWindowHandle(HWND hwnd) override;
  bool Capture() override;

  const RECT& GetWindowRect() const override { return windowRect_; }
  const RECT& GetClientRect() const override { return clientRect_; }
  int GetBitmapDataSize() const override { return bmpDataSize_; }
  HBITMAP GetBitmap() const override { return bitmap_; }
  void* GetBitmapAddress() const override { return bitsPtr_; }

protected:
  virtual bool InitDC(const BITMAPINFO& bitmapInfo) = 0;
  virtual bool DoCapture() = 0;

protected:
  HWND hwnd_;
  HDC scrDc_;
  HDC memDc_;
  HBITMAP bitmap_;
  HBITMAP oldBitmap_;
  void* bitsPtr_;

  RECT windowRect_;
  RECT clientRect_;
  int bmpDataSize_;
};

AbsCaptureHelper.cpp

#include "stdafx.h"
#include "AbsCaptureHelper.h"


AbsCaptureHelper::AbsCaptureHelper()
  : hwnd_(nullptr),scrDc_(nullptr),memDc_(nullptr),bitmap_(nullptr),oldBitmap_(nullptr),bitsPtr_(nullptr),windowRect_{ 0,0 },clientRect_{ 0,bmpDataSize_(0)
{
}

AbsCaptureHelper::~AbsCaptureHelper()
{
  AbsCaptureHelper::Cleanup();
}

bool AbsCaptureHelper::Init(const string& windowName)
{
  const auto handle = ::FindWindowA(nullptr,windowName.c_str());
  if (handle == nullptr)
  {
    return false;
  }

  return Init(handle);
}

bool AbsCaptureHelper::Init(HWND hwnd)
{
  hwnd_ = hwnd;

  //獲取視窗大小
  if (!::GetWindowRect(hwnd_,&windowRect_) || !::GetClientRect(hwnd_,&clientRect_))
  {
    return false;
  }

  const auto clientRectWidth = clientRect_.right - clientRect_.left;
  const auto clientRectHeight = clientRect_.bottom - clientRect_.top;
  bmpDataSize_ = clientRectWidth * clientRectHeight * 4;

  //點陣圖資訊
  BITMAPINFO bitmapInfo;
  bitmapInfo.bmiHeader.biSize = sizeof(bitmapInfo);
  bitmapInfo.bmiHeader.biWidth = clientRectWidth;
  bitmapInfo.bmiHeader.biHeight = clientRectHeight;
  bitmapInfo.bmiHeader.biPlanes = 1;
  bitmapInfo.bmiHeader.biBitCount = 32;
  bitmapInfo.bmiHeader.biSizeImage = clientRectWidth * clientRectHeight;
  bitmapInfo.bmiHeader.biCompression = BI_RGB;

  return InitDC(bitmapInfo);
}

void AbsCaptureHelper::Cleanup()
{
  if (bitmap_ == nullptr)
  {
    return;
  }

  //刪除用過的物件
  ::SelectObject(memDc_,oldBitmap_);
  ::DeleteObject(bitmap_);
  ::DeleteDC(memDc_);
  ::ReleaseDC(hwnd_,scrDc_);

  hwnd_ = nullptr;
  scrDc_ = nullptr;
  memDc_ = nullptr;
  bitmap_ = nullptr;
  oldBitmap_ = nullptr;
  bitsPtr_ = nullptr;
}

bool AbsCaptureHelper::RefreshWindow()
{
  const auto hwnd = hwnd_;
  Cleanup();
  return Init(hwnd);
}

bool AbsCaptureHelper::ChangeWindowHandle(const string& windowName)
{
  Cleanup();
  return Init(windowName);
}

bool AbsCaptureHelper::ChangeWindowHandle(HWND hwnd)
{
  Cleanup();
  return Init(hwnd);
}

bool AbsCaptureHelper::Capture()
{
  if (bitmap_ == nullptr || memDc_ == nullptr || scrDc_ == nullptr)
  {
    return false;
  }

  return DoCapture();
}

DibCaptureHelper.h

#pragma once

#include "AbsCaptureHelper.h"

class DibCaptureHelper : public AbsCaptureHelper
{
public:
  DibCaptureHelper();
  virtual ~DibCaptureHelper();

protected:
  bool InitDC(const BITMAPINFO& bitmapInfo) override;
  bool DoCapture() override;

private:
  bool saveBitmap_;
  int mockPageNumber;
  int bmpCount_;
};

DibCaptureHelper.cpp

#include "stdafx.h"
#include "DibCaptureHelper.h"
#include <sstream>

static int BmpCount = 0;
static int BmpMaxCount = 50;

DibCaptureHelper::DibCaptureHelper()
  : saveBitmap_(false),mockPageNumber(++BmpCount),bmpCount_(0)
{
}

DibCaptureHelper::~DibCaptureHelper()
{
}

bool DibCaptureHelper::InitDC(const BITMAPINFO& bitmapInfo)
{
  scrDc_ = ::GetWindowDC(hwnd_);
  memDc_ = ::CreateCompatibleDC(scrDc_);

  bitmap_ = ::CreateDIBSection(memDc_,&bitmapInfo,DIB_RGB_COLORS,&bitsPtr_,nullptr,0);
  if (bitmap_ == nullptr)
  {
    ::DeleteDC(memDc_);
    ::ReleaseDC(hwnd_,scrDc_);
    return false;
  }

  oldBitmap_ = static_cast<HBITMAP>(::SelectObject(memDc_,bitmap_));
  return true;
}

bool DibCaptureHelper::DoCapture()
{
  const auto clientRectWidth = clientRect_.right - clientRect_.left;
  const auto clientRectHeight = clientRect_.bottom - clientRect_.top;

  const auto ret = ::BitBlt(
    memDc_,clientRectWidth,clientRectHeight,scrDc_,SRCCOPY);

  return ret != 0;
}

PrintCaptureHelper.h

#pragma once

#include "AbsCaptureHelper.h"

class PrintCaptureHelper : public AbsCaptureHelper
{
public:
  PrintCaptureHelper();
  virtual ~PrintCaptureHelper();

protected:
  bool InitDC(const BITMAPINFO& bitmapInfo) override;
  bool DoCapture() override;
};

PrintCaptureHelper.cpp

#include "stdafx.h"
#include "PrintCaptureHelper.h"


PrintCaptureHelper::PrintCaptureHelper()
{
}

PrintCaptureHelper::~PrintCaptureHelper()
{
}

bool PrintCaptureHelper::InitDC(const BITMAPINFO& bitmapInfo)
{
  scrDc_ = ::GetWindowDC(hwnd_);
  memDc_ = ::CreateCompatibleDC(scrDc_);

  bitmap_ = ::CreateDIBSection(scrDc_,scrDc_);
    return false;
  }
  
  oldBitmap_ = static_cast<HBITMAP>(::SelectObject(memDc_,bitmap_));
  return true;
}

bool PrintCaptureHelper::DoCapture()
{
  const auto ret = ::PrintWindow(hwnd_,memDc_,PW_CLIENTONLY | PW_RENDERFULLCONTENT);
  return ret != 0;
}

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