GDI+方式截取系統屏幕

#include <iostream>
#include <Windows.h>
#include <GdiPlus.h>

using namespace std;

#pragma comment(lib, "gdiplus")

int GetEncoderClsid(const TCHAR *format, CLSID *pClsid)
{
        //using namespace Gdiplus;
        UINT num = 0;                // number of image encoders
        UINT size = 0;                // size of the image encoder array in bytes

        Gdiplus::ImageCodecInfo *pImageCodecInfo = NULL;

        Gdiplus::GetImageEncodersSize(&num, &size);

        if (size == 0)
                return -1;

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

        if (pImageCodecInfo == NULL)
                return -1;

        Gdiplus::GetImageEncoders(num, size, pImageCodecInfo);

        for (UINT j = 0; j < num; ++j)
        {
                if (_tcscmp(pImageCodecInfo[j].MimeType, format) == 0)
                {
                        *pClsid = pImageCodecInfo[j].Clsid;
                        free(pImageCodecInfo);
                        return j;
                }
        }

        free(pImageCodecInfo);
        return 0;
}

void CaptureScreenByGDIPlus()
{
        Gdiplus::GdiplusStartupInput gdiplusStartupInput;
        ULONG_PTR gdiplusToken;
        Gdiplus::GdiplusStartup(&gdiplusToken, &gdiplusStartupInput, NULL);

        {
                HDC scrdc = ::GetDC(NULL);

                int nHeight = GetSystemMetrics(SM_CYSCREEN);
                int nWidth = GetSystemMetrics(SM_CXSCREEN);

                HDC memdc = CreateCompatibleDC(scrdc);
                HBITMAP membit = CreateCompatibleBitmap(scrdc, nWidth, nHeight);

                HBITMAP hOldBitmap = (HBITMAP)SelectObject(memdc, membit);
                BitBlt(memdc, 0, 0, nWidth, nHeight, scrdc, 0, 0, SRCCOPY);

                Gdiplus::Bitmap bitmap(membit, NULL);
                CLSID clsid;
                GetEncoderClsid(_T("image/jpeg"), &clsid);
                bitmap.Save(_T("D:\\CaptureScreenByGDIPlus.jpg"), &clsid);

                SelectObject(memdc, hOldBitmap);

                DeleteObject(memdc);
                DeleteObject(membit);

                ReleaseDC(NULL, scrdc);
        }

        Gdiplus::GdiplusShutdown(gdiplusToken);
}