libnetpbm_draw (3) - Linux Manuals

libnetpbm_draw: Libnetpbm PPM Drawing Function Manual

NAME

libnetpbm_draw \- Libnetpbm PPM Drawing Function Manual

DESCRIPTION

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_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_set_font 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, because '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_read_font.

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_read_font

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_free_font

This function releases the handle that you get from ppmd_read_font. It frees resources associated with it; you can't use the handle after this.

ppmd_get_font

This function returns the handle of the currently selected font.

ppmd_set_font

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_read_font or ppmd_get_font.