Rendering fonts with Python
((c) João S. O. Bueno - jsbueno(at)python.org.br. Code license: CreativeCommons BY 3.0)
Using "helvetica" or "sans" fonts with Cairo only is easy with the "toyfont" api provided. However, for serious font work, one gets trapped as FreeType engine is not implemented. To the rescue, comes pango, and pangocairo - pango is a library created with the sole purpose of high quality text rendering.
Documentation on using pango along with cairo is scarce, and most examples are in C, - and those don't map straight into Python.
My system has all the libraries available - I suppose pangocairo comes along with the python-pango bindings.
The snippet bellow can render a sample text in a given font family, that can be specified as a command line parameter. It also prints the available font families to stdout.
# -*- coding: utf-8 -*-
import cairo
import pango
import pangocairo
import sys
surf = cairo.ImageSurface(cairo.FORMAT_ARGB32, 320, 120)
context = cairo.Context(surf)
#draw a background rectangle:
context.rectangle(0,0,320,120)
context.set_source_rgb(1, 1, 1)
context.fill()
#get font families:
font_map = pangocairo.cairo_font_map_get_default()
families = font_map.list_families()
# to see family names:
print [f.get_name() for f in font_map.list_families()]
#context.set_antialias(cairo.ANTIALIAS_SUBPIXEL)
# Translates context so that desired text upperleft corner is at 0,0
context.translate(50,25)
pangocairo_context = pangocairo.CairoContext(context)
pangocairo_context.set_antialias(cairo.ANTIALIAS_SUBPIXEL)
layout = pangocairo_context.create_layout()
fontname = sys.argv[1] if len(sys.argv) >= 2 else "Sans"
font = pango.FontDescription(fontname + " 25")
layout.set_font_description(font)
layout.set_text(u"Hello World")
context.set_source_rgb(0, 0, 0)
pangocairo_context.update_layout(layout)
pangocairo_context.show_layout(layout)
with open("cairo_text.png", "wb") as image_file:
surf.write_to_png(image_file)