C++实现屏幕截图

上回分享了一个全屏截图的代码，保存为BMP，参考：C++实现屏幕截图（全屏截图）

实际使用的过程中我发现截图文件实在大，无奈又整成了PNG截图，现在分享出来。

MakePNG.h

//MakePNG.h 

#pragma once
#include <GdiPlus.h>
using namespace Gdiplus;
#pragma comment(lib,"GdiPlus.lib") 

class CMakePNG
{
public:
 CMakePNG(void);
 ~CMakePNG(void); 

 BOOL MakePNG(HDC hDC,CRect rect,CString strFilePath);
 BOOL BMptoPNG(LPCWSTR StrBMp,LPCWSTR StrPNG);
 BOOL PNGtoBMp(LPCWSTR StrPNG,LPCWSTR StrBMp);
 BOOL GetEncoderClsid(WCHAR* pFormat,CLSID* pClsid);
private:
 GdiplusStartupInput m_gdiplusStartupInput;
 ULONG_PTR m_pGdiToken;
}; 

MakePNG.cpp

//MakePNG.cpp 

#include "StdAfx.h"
#include "MakePNG.h" 

CMakePNG::CMakePNG(void)
{
 GdiplusStartup(&m_pGdiToken,&m_gdiplusStartupInput,NULL);
} 

CMakePNG::~CMakePNG(void)
{
} 

/***************************************************************************/
/* 功能： 根据rect屏幕抓图，保存为文件名为strFilePath的PNG图像文件 */
/* 输入参数： HDC hDC   屏幕HDC；    */
/*  CRect rect  需要的矩形;   */
/*  CString strFilePath 保存文件全路径（含后缀名）; */
/***************************************************************************/
BOOL CMakePNG::MakePNG(HDC hDC, CRect rect, CString strFilePath)
{
 BITMAP bmp;
 PBITMAPINFO pbmi;
 PBITMAPINFOHEADER pbih; // bitmap info-header
 BITMAPFILEHEADER hdr; // bitmap file-header
 WORD cClrBits;
 LPBYTE lpBits;  // memory pointer
 DWORD dwTmp;
 DWORD cb;   // incremental count of bytes
 BYTE *hp;   // byte pointer
 HANDLE hfile;  // file handle
 CString szBMPFilename = strFilePath.Left(strFilePath.GetLength() - 3) + _T("bmp");//先保存成位图
 HDC hdcCompatible = CreateCompatibleDC(hDC);
 HBITMAP hbmScreen = CreateCompatibleBitmap(hDC, rect.Width(), rect.Height()); 

 if (hbmScreen == NULL)
 {
 AfxMessageBox(_T("CreateCompatibleBitmap() error"));
 return FALSE;
 } 

 // Select the bitmaps into the compatible DC. 

 if (!SelectObject(hdcCompatible, hbmScreen))
 {
 AfxMessageBox(_T("Compatible Bitmap Selection error"));
 return FALSE;
 } 

 //Copy color data for the entire display into a
 //bitmap that is selected into a compatible DC. 

 if (!BitBlt(hdcCompatible,
 0,0,
 rect.Width(), rect.Height(),
 hDC,
 rect.left,rect.top,
 SRCCOPY))
 {
 AfxMessageBox(_T("Screen to Compat Blt Failed"));
 return FALSE;
 } 

 // Retrieve the bitmap's color format, width, and height.
 if (!GetObject(hbmScreen, sizeof(BITMAP), (LPSTR)&bmp))
 {
 AfxMessageBox(_T("GetObject()出错！"));
 return FALSE;
 }
 // Convert the color format to a count of bits.
 cClrBits = (WORD)(bmp.bmPlanes * bmp.bmBitsPixel);
 if (cClrBits == 1)
 cClrBits = 1;
 else if (cClrBits <= 4)
 cClrBits = 4;
 else if (cClrBits <= 8)
 cClrBits = 8;
 else if (cClrBits <= 16)
 cClrBits = 16;
 else if (cClrBits <= 24)
 cClrBits = 24;
 else cClrBits = 32; 

 // Allocate memory for the BITMAPINFO structure. (This structure
 // contains a BITMAPINFOHEADER structure and an array of RGBQUAD
 // data structures.) 

 if (cClrBits != 24)
 pbmi = (PBITMAPINFO) LocalAlloc(LPTR,
 sizeof(BITMAPINFOHEADER) +
 sizeof(RGBQUAD) * (1<< cClrBits)); 

 // There is no RGBQUAD array for the 24-bit-per-pixel format. 

 else
 pbmi = (PBITMAPINFO) LocalAlloc(LPTR,
 sizeof(BITMAPINFOHEADER)); 

 // Initialize the fields in the BITMAPINFO structure. 

 pbmi->bmiHeader.biSize = sizeof(BITMAPINFOHEADER);
 pbmi->bmiHeader.biWidth = bmp.bmWidth;
 pbmi->bmiHeader.biHeight = bmp.bmHeight;
 pbmi->bmiHeader.biPlanes = bmp.bmPlanes;
 pbmi->bmiHeader.biBitCount = bmp.bmBitsPixel;
 if (cClrBits < 24)
 pbmi->bmiHeader.biClrUsed = (1<<cClrBits); 

 // If the bitmap is not compressed, set the BI_RGB flag.
 pbmi->bmiHeader.biCompression = BI_RGB; 

 // Compute the number of bytes in the array of color
 // indices and store the result in biSizeImage.
 pbmi->bmiHeader.biSizeImage = ((pbmi->bmiHeader.biWidth * cClrBits +31) & ~31) /8
 * pbmi->bmiHeader.biHeight;
 // Set biClrImportant to 0, indicating that all of the device colors are important.
 pbmi->bmiHeader.biClrImportant = 0; 

 pbih = (PBITMAPINFOHEADER) pbmi;
 lpBits = (LPBYTE) GlobalAlloc(GMEM_FIXED, pbih->biSizeImage); 

 if (!lpBits)
 {
 AfxMessageBox(_T("内存分配错误！"));
 return FALSE;
 }
 // Retrieve the color table (RGBQUAD array) and the bits
 // (array of palette indices) from the DIB.
 if (!GetDIBits(hDC, hbmScreen, 0, (WORD) pbih->biHeight, lpBits, pbmi,
 DIB_RGB_COLORS))
 {
 AfxMessageBox(_T("GetDIBits() error"));
 return FALSE;
 } 

 // Create the .BMP file.
 hfile = CreateFile(szBMPFilename,
 GENERIC_READ | GENERIC_WRITE,
 (DWORD) 0,
 NULL,
 CREATE_ALWAYS,
 FILE_ATTRIBUTE_NORMAL,
 (HANDLE) NULL);
 if (hfile == INVALID_HANDLE_VALUE)
 {
  AfxMessageBox(_T("创建文件失败"));
 return false;
 }
 hdr.bfType = 0x4d42; // 0x42 = "B" 0x4d = "M"
 // Compute the size of the entire file.
 hdr.bfSize = (DWORD) (sizeof(BITMAPFILEHEADER) +
 pbih->biSize + pbih->biClrUsed
 * sizeof(RGBQUAD) + pbih->biSizeImage);
 hdr.bfReserved1 = 0;
 hdr.bfReserved2 = 0; 

 // Compute the offset to the array of color indices.
 hdr.bfOffBits = (DWORD) sizeof(BITMAPFILEHEADER) +
 pbih->biSize + pbih->biClrUsed
 * sizeof (RGBQUAD); 

 // Copy the BITMAPFILEHEADER into the .BMP file.
 if (!WriteFile(hfile, (LPVOID) &hdr, sizeof(BITMAPFILEHEADER),
 (LPDWORD) &dwTmp, NULL))
 {
  AfxMessageBox(_T("写BMP文件头失败"));
 return FALSE;
 } 

 // Copy the BITMAPINFOHEADER and RGBQUAD array into the file.
 if (!WriteFile(hfile, (LPVOID) pbih, sizeof(BITMAPINFOHEADER)
 + pbih->biClrUsed * sizeof (RGBQUAD),
 (LPDWORD) &dwTmp, ( NULL)))
 {
  AfxMessageBox(_T("写BMP文件头失败"));
 return FALSE;
 } 

 // Copy the array of color indices into the .BMP file.
 cb = pbih->biSizeImage;
 hp = lpBits;
 if (!WriteFile(hfile, (LPSTR) hp, (int) cb, (LPDWORD) &dwTmp,NULL))
 {
 AfxMessageBox(_T("写入BMP文件失败"));
 return FALSE;
 } 

 // Close the .BMP file.
 if (!CloseHandle(hfile))
 {
  AfxMessageBox(_T("Can't close BMP file."));
 } 

 // Free memory.
 GlobalFree((HGLOBAL)lpBits); 

 //转换成PNG
 if(!BMptoPNG(szBMPFilename,strFilePath))
 {
 DeleteFile(szBMPFilename);
 return FALSE;
 }
 DeleteObject(hbmScreen);
 DeleteFile(szBMPFilename);
 return TRUE;
}
// //转换BMP文件为PNG文件
BOOL CMakePNG::BMptoPNG(LPCWSTR StrBMp,LPCWSTR StrPNG)
{
 CLSID encoderClsid;
 Status stat;
 Image* image = NULL;
 image = Bitmap::FromFile(StrBMp,TRUE);
 if (!GetEncoderClsid(L"image/png",&encoderClsid))
 {
 return FALSE;
 }
 stat = image->Save(StrPNG,&encoderClsid,NULL);
 if (stat != Ok)
 {
 return FALSE;
 }
 delete image;
 return TRUE;
} 

// 功能描述: 转换PNG文件为BMP文件
BOOL CMakePNG::PNGtoBMp(LPCWSTR StrPNG,LPCWSTR StrBMp)
{
 CLSID encoderClsid;
 Status stat;
 Image* pImage;
 pImage = Bitmap::FromFile(StrPNG,TRUE);
 if (!GetEncoderClsid(L"image/bmp",&encoderClsid))
 {
 return FALSE;
 }
 stat = pImage->Save(StrBMp,&encoderClsid,NULL);
 if (stat != Ok)
 {
 return FALSE;
 }
 delete pImage;
 return TRUE;
} 

BOOL CMakePNG::GetEncoderClsid(WCHAR* pFormat,CLSID* pClsid)
{
 UINT num = 0,size = 0;
 ImageCodecInfo* pImageCodecInfo = NULL;
 GetImageEncodersSize(&num,&size);
 if (size == 0)
 {
 return FALSE;
 }
 pImageCodecInfo = (ImageCodecInfo*)(malloc(size));
 if (pImageCodecInfo == NULL)
 {
 return FALSE;
 }
 GetImageEncoders(num,size,pImageCodecInfo);
 BOOL bfound = FALSE;
 for (UINT i = 0;!bfound && i < num; i++)
 {
 if (_wcsicmp(pImageCodecInfo[i].MimeType,pFormat) == 0)
 {
  *pClsid = pImageCodecInfo[i].Clsid;
  bfound = TRUE;
 }
 }
 free(pImageCodecInfo);
 return bfound;
} 

以上两个文件实际上是CMakePNG类，使用时需要把他们添加到项目中，调用方法如下：

wstring GetAppPathW()
{
 wchar_t szExePath[MAX_PATH] = {0};
 GetModuleFileNameW(NULL, szExePath, MAX_PATH);
 wchar_t *pstr = wcsrchr(szExePath, '\\');
 memset(pstr + 1, 0, 2);
 wstring strAppPath(szExePath);
 return strAppPath;
} 

// 屏幕截图
CString CDemoDlg::ScreenShot(void)
{
 CWnd *pDesktop = GetDesktopWindow();
 CDC *pDC = pDesktop->GetDC();
 CRect rect;
 //获取窗口的大小
 pDesktop->GetClientRect(&rect); 

 //保存到的文件名
 CString strFileName(GetAppPathW().c_str());
 strFileName += _T("ScreenShot\\");
 CreateDirectory((LPCTSTR)strFileName,NULL);
 CTime t = CTime::GetCurrentTime();
 CString tt = t.Format("%Y%m%d_%H%M%S");
 strFileName += tt;
 strFileName += _T(".PNG");
 //保存为PNG
 CMakePNG MakePNG;
 MakePNG.MakePNG(pDC->m_hDC,rect,strFileName);
 ReleaseDC(pDC);
 return strFileName;
} 

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