DynaPDF Manual - Page 767

Previous Page 766   Index   Next Page 768

Function Reference

Page 767 of 874

HFONT f = CreateFont(

-240,

// height of font

0,

// average character width

0,

// angle of escapement

0,

// base-line orientation angle

500,

// font weight

1,

// italic attribute option

0,

// underline attribute option

0,

// strikeout attribute option

Ansi_CHARSET,

// character set identifier

OUT_TT_ONLY_PRECIS,

// output precision

CLIP_DEFAULT_PRECIS, // clipping precision

ANTIALIASED_QUALITY, // output quality

FF_DONTCARE,

// pitch and family

"Arial")

// typeface name (Family Name)

nHeight

The GDI supports three modes how the font size or height can be specified. We want to discuss

negative values only because the other modes are not of interest for high precision output (positive

values specify the cell height of a font, this value must be converted by DynaPDF to determine the

wished font size). The font height we used in the example CreateFont() function call is defined as a

negative value. The absolute value of it is transformed to device units by the font mapper. We

choose a size of 240 units; this is a normal font size for a 1440 DPI output.

A negative font height in a CreateFont() function call is exactly the same as a positive height or size

in a SetFont() function call in DynaPDF (negative values are not supported by SetFont()).

However, GDI coordinates are normally upscaled because GDI functions support integer values

only. For example, if we want to use a font size of 12.74 units, we can only upscale the coordinate

system because it is impossible to define such a font size with a GDI function. That is the reason

why GDI drawings are defined in a specific resolution. GDI coordinates are never really device

independent.

However, to avoid issues with a fixed resolution the PDF format uses a completely different system

to produce device independent output. PDF coordinates and font sizes are expressed in floating

point units so that we can use our font size of 12.74 units directly. We do not need to upscale the

coordinate system and we don't need to consider whether the PDF file is drawn on a monitor or

printer. All the details about the output resolution are completely hidden for the user.

BTW - A PDF unit is 1/72 inch.

nWidth

The average character width (nWidth) is the same as horizontal text scaling in PDF (see

SetTextScaling()), but the calculation is completely different. The GDI uses the average character

width of a font to calculate the text scaling (the unscaled value is returned by the GDI function

GetTextMetrics() if nWidth was set to zero during font selection). So, the font must be selected into

Previous topic: How to use CJK encodings?, GDI Font selection in comparison to DynaPDF

Next topic: nEscapement, nOrientation, nWeight, fdwCharSet