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Libnetpbm PPM Drawing Function Manual
Updated: September 2005
Table Of Contents
This reference manual covers
functions in the libnetpbm library for drawing
images, using the PPM image format and the libnetpbm
in-memory image
formats.
We actually have very little
information here; this is mainly a framework
for adding documentation later if someone becomes interested
in this
facility.
The Functions
The functions are all declared in the ppmdraw.h header file.
ppmd_point_drawproc
ppmd_setlinetype
ppmd_setlineclip
ppmd_line
ppmd_spline3
ppmd_polyspline
ppmd_circle
ppmd_filledrectangle
ppmd_fill_init
ppmd_fill_drawproc
ppmd_fill
ppmd_text
ppmd_text_box
Fonts
The ppmd_text and ppmd_text_box
functions use fonts. You control the fonts
using functions described in this section. There is one font
that comes with
Netpbm, called "standard". It is built into the
function library and is the
default font. You can create additional fonts and use them
instead.
In a program that uses Netpbm
drawing facilities, there is a "current font."
all drawing of text uses the current font. When the program
starts, the
current font is "standard"; you can change it
after that by calling the
ppmd_setfont function.
Other than a built-in font, a
font lives in file in a format special to
Netpbm called Ppmdfont. The file typically has a name that
ends in
".ppmdfont".
Use the ppmddumpfont program to
dump the contents of a Ppmdfont file in
human readable format.
Use the ppmdmkfont program to
generate the "standard" font as a Ppmdfont
file. You don’t normally need to do this, becuase
"standard" is built into
libnetpbm.
Use the ppmdcfont program to
turn a Ppmdfont file into a C source file that
you can compile into a program as a built-in font. Though we
don’t give full
instructions here on how to do that, libnetpbm’s
built-in "standard" font is
a good example. In Netpbm source code, you will find the C
source file
standardppmdfont.c, which was generated from the file
standard.ppmdfont by
ppmdcfont. You simply use a pointer to the structure that
the C file defines
as a font handle, just like one you would get from
ppmd_readfont.
Font File Format
The font file starts with the
characters "ppmdfont" (without the quotation
marks) in ASCII.
The rest of the format is not
yet documented, but it generally describes,
for each code point, a sequence of straight line plotting
commands to form
the glyph for the indicated character. I.e. it is a vector,
not raster,
font.
Font Control Functions
These functions are declared in the header file ppmdfont.h.
ppmd_readfont
This function associates a
Ppmdfont file, which you identify by naming the
Ppmdfont file, with a handle that you can use to identify
the font to other
functions. Technically, this function reads the font into
memory.
ppmd_freefont
This function releases the
handle that you get from ppmd_readfont. It frees
resources associated with it; you can’t use the handle
after this.
ppmd_getfont
This function returns the handle of the currently selected font.
ppmd_setfont
This function sets the currently
selected font. You identify the font to
which to set it with a handle such as you get from
ppmd_readfont or
ppmd_getfont.
_________________________________________________________________
Table Of Contents
* The Functions
* Fonts
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