How does one print from a document from a memory dc

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How can I write from a memory device context to a printer device context using StretchBlt considering differences in resolution between the printer and the window that the memory device context is compatible with.

What I have tried:

I have been searching on-line for this for months.

Posted 23-May-24 5:43am

Gbenbam

Updated 23-May-24 6:13am

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Rick York 23-May-24 12:25pm

That is a rather curious design if that is what you have to do. I have written a lot of programs that do rendering both 2D (usually GDI+) and 3D (OpenGL, see my profile) and they are almost always double buffered and I have never had a persistent memory DC. It is always drawn to, written to the device, and then automatically deleted. That means this topic has never come up for me because I always do printing from the device. Why do you need to print from the memory context? Also - the printer and device (nearly) always have different resolutions so why does that make a difference in this case?

Gbenbam 23-May-24 14:19pm

I currently write write to window dc using double buffering, but write direct to printer. But the printed version vision is not a replica of the window version. Users might be displeased. So, i am thinking to use double buffering for printing too, but I want to know how to handle difference in resolution issues. I felt using stretch but to write from a window compatible dc to printer using a scale factor that factors in resolution might work. What do you think?

Richard MacCutchan 23-May-24 12:26pm

The same way that you write to the screen. You need to look into the use of the different MAPMODES that are used in order to map the image onto the printer.

Gbenbam 23-May-24 14:20pm

I sure know about mapping modes. See my response to Rick York above.

Richard MacCutchan 24-May-24 5:09am

I have some code that may help you, but it is too long to post here. If you go to Re: rfcomm ? - Linux Programming Discussion Boards[^] and click on the Email link below my message, you can send me a private message. I can then reply to that and send you my code as a complete VS project.

Gbenbam 24-May-24 10:28am

I have searched again and again.I could not find an email link there. Can you give me some more guidance?

Richard MacCutchan 24-May-24 10:35am

Sorry about that, it seems the link is only available to members with a higher number of points. If you put a reply to that message of mine, and make sure you tick the box marked "Allow private email replies to this message", then we can (I hope) deal with this without making our emails public.

Gbenbam 24-May-24 13:48pm

Thank you. I appreciate your assistance. I will do that right away.

Gbenbam 25-May-24 13:02pm

I don't think that will work dump it this google drive location:

https://drive.google.com/drive/folders/1edgHHWJcknOlJnf7rXu3NmmtGtG0URKP?usp=sharing

Richard MacCutchan 26-May-24 7:09am

Zip file uploaded, good luck.

Gbenbam 26-May-24 8:45am

Thank you.

Gbenbam 8-Jun-24 12:13pm

I thought I should give you feedback and thank you. The vs project had the information I sought and has helped me to effect printing with StretchBlt. Once again,thank you.

Richard MacCutchan 8-Jun-24 12:14pm

Thanks, you are welcome.

Gbenbam 9-Jun-24 20:16pm

I just shared my code.

2 solutions

Solution 1

The concept of the device context DC is the abstraction of the peripheral device attached to the computer. You draw or print in exactly same way to all of them. So, if you have function say like in MFC OnDraw(CDC* pDC) - if you pass the screen CDC it will draw onto the screen. If you pass Printer CDC it will draw to your printer. Same goes for plotter, fax or whatever is supported by windows.

Posted 23-May-24 9:37am

steveb

Comments

Gbenbam 23-May-24 21:35pm

What about resolution? Of course my function wires successfully . to printer. The issue is that what was printed is not a replica of what was displayed on the screen because of differences in resolution.

For instance, I use the GDI+- function which draws the images as desired to windows without hassles but the exact same function drew something way way bigger on printer. I had to read documentation long enough to find out that GDI+ graphics function can be set to draw u device units like millimetre . Setting display unit of graphics class resolved the issue, but not completely. The position of the images were not a exact replica of what was displayed in that they were not drawn to perspective in terms of positioning. I had to add printer specific codes.

steveb 24-May-24 21:49pm

If I remember correctly you need to call GetDeviceCaps with X and Y parameter and this should be applied to rectangles, coordinates, etc. For screen those usually always equal 1 but for printers depends. I saw 9 for printer. If you have MFC installed peek inside CPreviewView (They use those methods everywhere)

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Gbenbam · Accepted Answer · 2024-06-09T14:15:00

Below is a sample code.

C++

void PrintDocument(
	HDC	hPrinterDC,
	HDC hMemoryDC,
	int iSourceWidth,
	int iSourceHeight

	)
{
	POINT destSize{};
	destSize.x = iSourceWidth;
	destSize.y = iSourceHeight;

	double dMemoryDCX = GetDeviceCaps(hMemoryDC, LOGPIXELSX);	// and the dimensions of the memoryDC
	double dMemoryDCY = GetDeviceCaps(hMemoryDC, LOGPIXELSY);
	double dDeviceX = GetDeviceCaps(hPrinterDC, LOGPIXELSX);		// and the target device
	double dDeviceY = GetDeviceCaps(hPrinterDC, LOGPIXELSY);

	//Calculate scale factor
	double dScaleFactorX = dDeviceX / dMemoryDCX;
	double dScaleFactorY = dDeviceY / dMemoryDCY;

	destSize.x = static_cast<int>(destSize.x * dScaleFactorX);
	destSize.y = static_cast<int>(destSize.y * dScaleFactorY);
	DPtoLP(hPrinterDC, &destSize, 1);

	// Blit it on to the printerDC, stretching or compressing as necessary
	StretchBlt(hPrinterDC,
		0,	// destination X position
		0,		// destination Y position
		destSize.x,			// destination width
		destSize.y,			// destination height
		hMemoryDC, 0,0,		// source start
		iSourceWidth		// source image width
		iSourceHeight,	//       ..     height
		SRCCOPY);			// how to blit

}