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"""Utility functions for cairo-specific operations"""
import cairo, pygame, struct
big_endian = struct.pack( '=i', 1 ) == struct.pack( '>i', 1 )
def newContext( width, height ):
"""Create a new render-to-image context
width, height -- pixel dimensions to be rendered
returns surface, context for rendering
"""
csrf = cairo.ImageSurface(cairo.FORMAT_ARGB32, width, height)
return csrf, cairo.Context (csrf)
def mangle_color(color):
"""Mange a colour depending on endian-ness, and swap-necessity
This implementation has only been tested on an AMD64
machine with a get_data implementation (rather than
a get_data_as_rgba implementation).
"""
r,g,b = color[:3]
if len(color) > 3:
a = color[3]
else:
a = 255.0
return map(_fixColorBase, (r,g,b,a) )
def _fixColorBase( v ):
"""Return a properly clamped colour in floating-point space"""
return max((0,min((v,255.0))))/255.0
def asImage( csrf ):
"""Get the pixels in csrf as a Pygame image
Note that Pygame 1.7.1 on Gentoo AMD64 is incorrectly calculating
the required size of the arrays, so this code will *not* work on that
platform with that version of the library. Pygame-ctypes does work
correctly.
"""
# Create and return a new Pygame Image derived from the Cairo Surface
format = 'ARGB'
if hasattr(csrf,'get_data'):
# more recent API, native-format, but have to (potentially) convert the format...
data = csrf.get_data()
if not big_endian:
# we use array here because it's considerably lighter-weight
# to import than the numpy module
import array
a = array.array( 'I' )
a.fromstring( data )
a.byteswap()
data = a.tostring()
else:
data = str(data) # there's one copy
else:
# older api, not native, but we know what it is...
data = csrf.get_data_as_rgba()
data = str(data) # there's one copy
width, height = csrf.get_width(),csrf.get_height()
try:
return pygame.image.fromstring(
data,
(width,height),
format
) # there's the next
except ValueError, err:
err.args += (len(data), (width,height), width*height*4,format )
raise
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