C++实现的屏幕截图（PNG或BMP）

上回分享了一个全屏截图的代码，保存为BMP，

C++实现屏幕截图（全屏截图）：/article/10914848.html

实际使用的过程中我发现截图文件实在大，无赖又整成了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;
}