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Printing using GDI+ : a few tips

, 10 Sep 2002
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A few "specialized" tips on printing figures using GDI+

Introduction

This articles gives some hints on printing figure made with GDI+. As anybody knows, printing is one of the most mysterious feature in MFC (this is my point of view). It is not well (at all) documented and in fact, the best examples can be found in CodeProject Printing section.

Since GDI+ is a new technology, it brings new problems when trying to print.

In the following, I will try to give some hints encountered when trying to print GDI+ stuff. I will suppose that you have some basic knowledge about printing, especially that you have read one of the following articles, so I won't have to discuss about getting a printer DC working and other details already in those article but rather focus on GDI+ problem related:

In the following, dc denotes the printer dc and graphics denotes the GDI+ graphic context:

    CDC dc;
    Graphics graphics;

Setting the mapping modes

The mapping modes of dc and graphics must be tuned together:

    dc.SetMapMode(MM_TEXT);
    graphics.SetPageUnit(UnitDocument); 

With those setting, each logical unit is converted to 1 device unit (MM_TEXT) and one device unit is 1/300 inch (UnitDocument). So we get 300dpi printing, great.

What about other DPIs?

Gulp, we got it working for 300dpi, but what about 600 dpi? or 1200 ?

After a few try and error, I figured out we had to do the dirty job ourselves, that is check for the dpi of printer and scale accordingly the graphic:

  1. Get the dpi ratio dpiRatio:
        CPrintDialog MyPrintDialog;
         ...
         // the dpi of printer is enclosed in DEVMODE structure,
         DEVMODE* pDev=MyPrintDialog.GetDevMode();
        // getting dpi ratio between 300dpi and current printer dpi
        double dpiRatio=300.0/pDev->dmPrintQuality;
        // deallocating memory for pDev
        VERIFY(GlobalUnlock(pDev));
    
  2. Setting page scale in to graphics
        graphics.SetPageScale(dpiRatio);
    

That ugly hack should do the work. Of course, any nicer method is welcome Smile | :)

What about text?

Getting font size

Unfortunately, scaling the graphic is not sufficient and Dpi scaling has to be taken in account when computing the font size!

Here's a modification of the CreateFontSize of Barnhart article. As you see, the user has to pass the dpiRatio to scale the font accordingly:

int CreateFontSize(HDC hDC, int points, double dpiRatio)
{
	// This will calculate the font size for the printer that is specified
	// by a point size.
	//
	// if points is:
	//  (-) negative uses height as value for Net Font Height (ie. point size)
	//	(+) positive height is Total Height plus Leading Height!
	ASSERT(hDC);
	
	POINT size;
	int logPixelsY=::GetDeviceCaps(hDC, LOGPIXELSY);
	size.x = size.y = MulDiv(points, logPixelsY, 72);

	// here we scale the font...
	return (float)floor(size.y*dpiRatio);
}

Create font for printing

When creating a font, use the following unit:
Unit fontUnit = m_pGraphics->GetPageUnit();
// if fontUnit is UnitDisplay, then specify UnitPixel, 
// otherwise you'll get a "InvalidParameter" from GDI+
if (fontUnit == UnitDisplay)
fontUnit = UnitPixel;
// classical constructor use, lfHeight is the font height
Font font(&fontFamily, CreateFontSize(hDC, 
          lfHeight, dpiRatio), FontStyleRegular, fontUnit);

Credits

A lot of useful article available on the Printing section:

Update History

11/09/2002Fixed problem of text changing size when playing with the zoom in preview mode. Updated the demo project.

License

This article has no explicit license attached to it but may contain usage terms in the article text or the download files themselves. If in doubt please contact the author via the discussion board below.

A list of licenses authors might use can be found here

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About the Author

Jonathan de Halleux
Engineer
United States United States
Jonathan de Halleux is Civil Engineer in Applied Mathematics. He finished his PhD in 2004 in the rainy country of Belgium. After 2 years in the Common Language Runtime (i.e. .net), he is now working at Microsoft Research on Pex (http://research.microsoft.com/pex).

Comments and Discussions

 
GeneralMy vote of 5 Pinmembermanoj kumar choubey18-Feb-12 1:09 
GeneralAnother solution: Pinmemberommail18-Sep-08 22:40 
GeneralRe: Another solution: PinmemberShaunBloodsworth10-May-12 11:54 
GeneralError Pinmemberdanandu17-Apr-08 1:14 
GeneralGDI/GDI+ printing stuff... PinmemberAlberto_Canabal23-Jan-06 3:20 
GeneralPrinting to file Pinmemberanup_zade5-Jul-05 0:27 
Generaltransparency PinmemberDieter Hammer7-Dec-04 4:31 
Generalprinting problems using GDI+ enhanced metafile Pinmemberpdehon20-Oct-04 2:55 
QuestionHow to save GDI+ bmp as CMYK color GDI+ bmp Pinsusspubba28-May-04 0:49 
GeneralAnother Solution PinmemberFlyingHero5-Nov-03 17:10 
GeneralRe: Another Solution Pinmemberbob1697215-Jun-05 13:18 
GeneralRe: Another Solution PinmemberLars [Large] Werner19-Jun-06 10:39 
GeneralRe: Another Solution Pinmembernohara12-Jul-06 10:39 
GeneralPreview problem PinmemberDrFretBoard23-Dec-02 2:55 
Generalquestion about CPrintDialog and DEVMODE Structure Pinmemberlavocat2-Dec-02 1:38 
GeneralNew to GDI+ Printer PinsussLarsi21-Oct-02 3:59 
GeneralRe: New to GDI+ Printer Pinmemberwickywang28-Dec-04 22:57 
GeneralText Printing As Garbage PinmemberBrian Vollmer1-Oct-02 12:42 
GeneralComments PineditorNishant S1-Aug-02 15:42 
GeneralPrint preview... PinmemberJonathan de Halleux11-Sep-02 0:29 
GeneralSome good tips PinmemberRoger Allen30-Jul-02 3:30 
Generalnice but... PinmemberMario M.29-Jul-02 15:38 
GeneralDone PinmemberJonathan de Halleux30-Jul-02 5:23 

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