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POHow can I take a screenshot and save it as JPEG on Windows?
 

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  1. POHow can I take a screenshot and save it as JPEG on Windows?
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    <p>I'm trying to find a (somewhat) easy way to take a screenshot on window and save the resulting HBITMAP as a JPEG. The tricky part here is that since the code is in C I can't use GDI+ and since the code is a module for a bigger program I can't neither use an external lib (like libjpeg).</p> <p>This code takes a screenshot and returns a HBITMAP. Saving that bitmap into a file is easy. the problem is that the bitmap is 2 or 3mb.</p> <pre><code>HDC hDCMem = CreateCompatibleDC(NULL); HBITMAP hBmp; RECT rect; HDC hDC; HGDIOBJ hOld; GetWindowRect(hWnd, &amp; rect); hBmp = NULL; { hDC = GetDC(hWnd); hBmp = CreateCompatibleBitmap(hDC, rect.right - rect.left, rect.bottom - rect.top); ReleaseDC(hWnd, hDC); } hOld = SelectObject(hDCMem, hBmp); SendMessage(hWnd, WM_PRINT, (WPARAM) hDCMem, PRF_CHILDREN | PRF_CLIENT | PRF_ERASEBKGND | PRF_NONCLIENT | PRF_OWNED); SelectObject(hDCMem, hOld); DeleteObject(hDCMem); return hBmp; </code></pre> <p>any ideas on how to do this? thanks so much, any help is appreciated</p> <p>EDIT: Since we went in the direction of GDI+ I thought I'd post the code iv C++ that can take the screenshot and convert it to a JPEG using GDI+. If anyone knows how to achieve this using the FLAT GDI+ i'd appreciate the help. Code:</p> <pre><code> #include &lt;windows.h&gt; #include &lt;stdio.h&gt; #include &lt;gdiplus.h&gt; using namespace Gdiplus; int GetEncoderClsid(WCHAR *format, CLSID *pClsid) { unsigned int num = 0, size = 0; GetImageEncodersSize(&amp;num, &amp;size); if(size == 0) return -1; ImageCodecInfo *pImageCodecInfo = (ImageCodecInfo *)(malloc(size)); if(pImageCodecInfo == NULL) return -1; GetImageEncoders(num, size, pImageCodecInfo); for(unsigned int j = 0; j &lt; num; ++j) { if(wcscmp(pImageCodecInfo[j].MimeType, format) == 0){ *pClsid = pImageCodecInfo[j].Clsid; free(pImageCodecInfo); return j; } } free(pImageCodecInfo); return -1; } int GetScreeny(LPWSTR lpszFilename, ULONG uQuality) // by Napalm { ULONG_PTR gdiplusToken; GdiplusStartupInput gdiplusStartupInput; GdiplusStartup(&amp;gdiplusToken, &amp;gdiplusStartupInput, NULL); HWND hMyWnd = GetForegroundWindow(); // get my own window RECT r; // the area we are going to capture int w, h; // the width and height of the area HDC dc; // the container for the area int nBPP; HDC hdcCapture; LPBYTE lpCapture; int nCapture; int iRes; CLSID imageCLSID; Bitmap *pScreenShot; HGLOBAL hMem; int result; // get the area of my application's window //GetClientRect(hMyWnd, &amp;r); GetWindowRect(hMyWnd, &amp;r); dc = GetWindowDC(hMyWnd);// GetDC(hMyWnd) ; w = r.right - r.left; h = r.bottom - r.top; nBPP = GetDeviceCaps(dc, BITSPIXEL); hdcCapture = CreateCompatibleDC(dc); // create the buffer for the screenshot BITMAPINFO bmiCapture = { sizeof(BITMAPINFOHEADER), w, -h, 1, nBPP, BI_RGB, 0, 0, 0, 0, 0, }; // create a container and take the screenshot HBITMAP hbmCapture = CreateDIBSection(dc, &amp;bmiCapture, DIB_PAL_COLORS, (LPVOID *)&amp;lpCapture, NULL, 0); // failed to take it if(!hbmCapture) { DeleteDC(hdcCapture); DeleteDC(dc); GdiplusShutdown(gdiplusToken); printf("failed to take the screenshot. err: %d\n", GetLastError()); return 0; } // copy the screenshot buffer nCapture = SaveDC(hdcCapture); SelectObject(hdcCapture, hbmCapture); BitBlt(hdcCapture, 0, 0, w, h, dc, 0, 0, SRCCOPY); RestoreDC(hdcCapture, nCapture); DeleteDC(hdcCapture); DeleteDC(dc); // save the buffer to a file pScreenShot = new Bitmap(hbmCapture, (HPALETTE)NULL); EncoderParameters encoderParams; encoderParams.Count = 1; encoderParams.Parameter[0].NumberOfValues = 1; encoderParams.Parameter[0].Guid = EncoderQuality; encoderParams.Parameter[0].Type = EncoderParameterValueTypeLong; encoderParams.Parameter[0].Value = &amp;uQuality; GetEncoderClsid(L"image/jpeg", &amp;imageCLSID); iRes = (pScreenShot-&gt;Save(lpszFilename, &amp;imageCLSID, &amp;encoderParams) == Ok); delete pScreenShot; DeleteObject(hbmCapture); GdiplusShutdown(gdiplusToken); return iRes; } </code></pre>
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    1. COdoes it really have to be a JPG? if a PNG is ok you could use libpng..
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      1. POHow can I take a screenshot and save it as JPEG on Windows?
      1. USsean riley
    2. COYes, it has to be JPG. PNG is not small enough for what I need. Besides, I can't use external or 3rd party libs. libpng it's big and it adds a lot of extra code that I don't need (i tried this already) Thanks for the answer tho.
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      1. POHow can I take a screenshot and save it as JPEG on Windows?
      1. USwonderer
    3. COJPG is not good choice for screenshots. It's much better for photos and like, but for screenshots PNG provides much better results. You can make it smaller by scaling down or color bit depth reduction.
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      1. POHow can I take a screenshot and save it as JPEG on Windows?
      1. USAndriy Tylychko
 

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