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surface_write_to_png.py

#!/usr/bin/env python
"""
Test Surface.write_to_png()
"""

import cStringIO
import math
import sys
import StringIO

import cairo


00014 class C(object):
    """a file-like object (for testing), it simulates sys.stdout
    """
    def __init__ (self):
        self.closed = False

00020     def write(self, s):
        """just echo to stdout, without newlines"""
        if self.closed:
            raise ValueError ("I/O operation on closed file")
        sys.stdout.write (s)

    def close(self):
        self.closed = True


WIDTH, HEIGHT  = 256, 256

surface = cairo.ImageSurface (cairo.FORMAT_ARGB32, WIDTH, HEIGHT)
ctx = cairo.Context (surface)

ctx.scale (WIDTH/1.0, HEIGHT/1.0)

pat = cairo.LinearGradient (0.0, 0.0, 0.0, 1.0)
pat.add_color_stop_rgba (1, 0, 0, 0, 1)
pat.add_color_stop_rgba (0, 1, 1, 1, 1)

ctx.rectangle (0,0,1,1)
ctx.set_source (pat)
ctx.fill ()

pat = cairo.RadialGradient (0.45, 0.4, 0.1,
                            0.4,  0.4, 0.5)
pat.add_color_stop_rgba (0, 1, 1, 1, 1)
pat.add_color_stop_rgba (1, 0, 0, 0, 1)

ctx.set_source (pat)
ctx.arc (0.5, 0.5, 0.3, 0, 2 * math.pi)
ctx.fill ()

# a selection of possible args to surface.write_to_png()
#fo = '/tmp/f.png'
fo = file('/tmp/f.png', 'w')
#fo = StringIO.StringIO()
#fo = cStringIO.StringIO()
#fo = sys.stdout
#fo = C()

fo.close()  # this should cause: ValueError: I/O operation on closed file
surface.write_to_png (fo)

# for testing StringIO: get data and write to file
#string = fo.getvalue()
#f2 = file('/tmp/f.png', 'w')
#f2.write(string)
#f2.close()

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