C / C++ / MFC

/*---------------------------------------------------------------------------
  This will create and Memory Device context and copy the bitmap given onto
  that memory context. Fail will return NULL as a memory context. 
  Caller takes responsibility for disposal of the device context.
  --------------------------------------------------------------------------*/
HDC BitmapToMemDc (HBITMAP hBmp)
{
   HDC hMemDC = 0;     // Preset memory context fail
   if (hBmp != 0)      // Check bitmap handle valid
   {
      hMemDC = CreateCompatibleDC(NULL);   // Create memory context
      if (hMemDC)                          // Check memory context success
      {
         SelectObject(hMemDC, hBmp);	   // Select the bitmap to the context	
      }
   }
   return hMemDC; // Return the memory context
}

/*---------------------------------------------------------------------------
  This will create and Memory Device context of the the bitmap filename given
  Caller must take responsibility for disposal of the device context.
  --------------------------------------------------------------------------*/
HDC MemDCFromBMPFile(char* Filename)
{
   HDC MemDC = 0;                               // Preset return value to fail
   HBITMAP bmp = LoadBitmapFromFile(Filename);	// Load the bitmap
   if (bmp != 0)                                // Load bitmap was successful
   {
      MemDC = BitmapToMemDc(bmp);		// Create a memory context of a valid bitmap  
      DeleteObject(bmp);                        // Release the bitmap no longer needed (image on memDC)
   }		
   return MemDC;   // Return result
}

#include "olectl.h"   // OLE is used for JPG image loading

/*---------------------------------------------------------------------------
  Creates a Memory Device context of the the JPEG/GIF filename given.
  Due to the way OLE works filename must be fully qualified (ie c:\folder\a.jpg)
  You can not assume the loading directory is the current directory.
  Caller must take responsibility for disposal of the device context.
  --------------------------------------------------------------------------*/
HDC MemDCFromJPG_GIF_File(char* filename)
{
	const int HIMETRIC_PER_INCH = 2540;
	WCHAR OlePathName[512];
	SIZE sizeInHiMetric;
	IPicture* Ipic = NULL;

	HDC MemDC = 0;     // Preset return value to fail
	MultiByteToWideChar(CP_ACP, 0, filename,
		(int)strlen(filename) + 1, &OlePathName[0], 512);	// Convert console ansi filename to unicode
	HRESULT hr = OleLoadPicturePath(OlePathName, NULL, 0, 0,
		IID_IPicture, (LPVOID*)&Ipic);		   // Load the picture
	if ((hr == S_OK) & (Ipic != 0))    // Picture loaded okay						
	{
		int Wth, Ht;
		HDC Dc = GetDC(NULL);	// Get screen DC
		int nPixelsPerInchX = GetDeviceCaps(Dc, LOGPIXELSX);  // Screen X pixels per inch 
		int nPixelsPerInchY = GetDeviceCaps(Dc, LOGPIXELSY); // Screen Y pixels per inch
		ReleaseDC(NULL, Dc);	// Release screen DC
		Ipic->get_Width(&sizeInHiMetric.cx);	// Get picture witdh in HiMetric
		Ipic->get_Height(&sizeInHiMetric.cy);	// Get picture height in HiMetric
		Wth = (nPixelsPerInchX * sizeInHiMetric.cx +
			HIMETRIC_PER_INCH / 2) / HIMETRIC_PER_INCH;	// Calculate picture width in pixels
		Ht = (nPixelsPerInchY * sizeInHiMetric.cy +
			HIMETRIC_PER_INCH / 2) / HIMETRIC_PER_INCH;	// Calculate picture height in pixels
		MemDC = CreateCompatibleDC(0);		// Create a memory device context
		if (MemDC)
		{
			BITMAPINFO	bi = { 0 };
			DWORD* pBits = 0;
			bi.bmiHeader.biSize = sizeof(BITMAPINFOHEADER);	// Set Structure Size
			bi.bmiHeader.biBitCount = 32;	// 32 Bit
			bi.bmiHeader.biWidth = Wth;  	// Image Width
			bi.bmiHeader.biHeight = Ht;		// Image Height
			bi.bmiHeader.biCompression = BI_RGB; // RGB Encoding
			bi.bmiHeader.biPlanes = 1;  	// 1 Bitplane
			HBITMAP bmp = CreateDIBSection(MemDC, &bi, DIB_RGB_COLORS,
				(void**)&pBits, 0, 0);		// Create a DIB section
			if (bmp)
			{
				SelectObject(MemDC, bmp); // Select the bitmap to the memory context															
				Ipic->Render(MemDC, 0, 0, Wth, Ht, 0,
					sizeInHiMetric.cy, sizeInHiMetric.cx,
					-sizeInHiMetric.cy, NULL);	// Render the image to the DC
				DeleteObject(bmp);	  // Delete the bitmap we are done with it
			}
		}
		Ipic->Release();      // Finished with IPic
	}
	return MemDC;  // Return the memory context
}

Due to the way OLE works filename must be fully qualified (ie c:\folder\a.jpg)

charlieg wrote:

Oh if this works, Christmas has come early! I'll check it out.

#include "stdio.h"
#include "conio.h"

int main()
{
    char c;
    c = _getch();
    putchar('*');
    printf("\nYou entered %c\n", c);
    _getch(); // just to pause the program before closing the output console
    return 0;
}

$ cat example.c
#include <stdio.h>

int main()
{
    int n;
    printf("&n = %p\n" , &n);
}
$ for ((i=0;i<4;++i)); do ./example; done
&n = 0x7fff2ddda67c
&n = 0x7ffdece1243c
&n = 0x7ffe42e7d2bc
&n = 0x7fffd2e78b2c
$