1 files changed, 135 insertions, 0 deletions
diff --git a/olpcgames/_cairoimage.py b/olpcgames/_cairoimage.py
new file mode 100755
index 0000000..3cfa22c
--- /dev/null
+++ b/olpcgames/_cairoimage.py
@@ -0,0 +1,135 @@
+"""Utility functions for cairo-specific operations
+
+USE_BASE_ARRAY -- if False (default), uses numpy arrays,
+    currently this is the only version that works on 32-bit
+    machines.
+"""
+import pygame, struct, logging
+big_endian = struct.pack( '=i', 1 ) == struct.pack( '>i', 1 )
+
+log = logging.getLogger( 'olpcgames._cairoimage' )
+##log.setLevel( logging.DEBUG )
+
+USE_BASE_ARRAY = False
+
+def newContext( width, height ):
+    """Create a new render-to-image context
+    
+    width, height -- pixel dimensions to be rendered
+    
+    Produces an ARGB format Cairo ImageSurface for 
+    rendering your data into using rsvg, Cairo or Pango.
+    
+    returns (ImageSurface, CairoContext) for rendering
+    """
+    import cairo
+    csrf = cairo.ImageSurface(cairo.FORMAT_ARGB32, width, height)
+    context = cairo.Context (csrf)
+    #log.info( 'Format (expect: %s): %s', cairo.FORMAT_ARGB32, csrf.get_format())
+    return csrf, context
+
+def mangle_color(color):
+    """Mange a colour depending on endian-ness, and swap-necessity
+    
+    Converts a 3 or 4 int (or float) value in the range 0-255 into a 
+    4-float value in the range 0.0-1.0
+    """
+    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 Linux) AMD64 is incorrectly 
+    calculating the required size ARGB images, so this code will *not* work 
+    on that  platform with that version of the library.  Pygame-ctypes 
+    does work correctly there.
+    
+    Note also that Pygame 1.7.1 is showing a strange colour rotation 
+    bug on 32-bit platforms, such that ARGB mode cannot be used for 
+    images there.  Instead we have to do an expensive bit-shift operation
+    to produce an RGBA image from the ARGB native Cairo format.
+    
+    Will raise a ValueError if passed a Null image (i.e. dimension of 0)
+    
+    returns Pygame.Surface (image) with convert_alpha() called for it.
+    """
+    # 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...
+        log.debug( 'Native-mode api (get_data)' )
+        data = csrf.get_data()
+        if not big_endian:
+            # we use array here because it's considerably lighter-weight
+            # to import than the numpy module
+            log.debug( 'Not big-endian, byte-swapping array' )
+            if USE_BASE_ARRAY:
+                import array
+                a = array.array( 'I' )
+                a.fromstring( data )
+                a.byteswap()
+                data = a.tostring()
+            else:
+                import numpy 
+                n = numpy.fromstring( data, dtype='I' )
+                n =  ((n & 0xff000000) >> 24  ) | ((n & 0x00ffffff) << 8 )
+                n = n.byteswap()
+                data = n.tostring()
+                format = 'RGBA'
+        else:
+            log.debug( 'Big-endian, array unchanged' )
+            data = str(data) # there's one copy
+    else:
+        # older api, not native, but we know what it is...
+        log.debug( 'Non-native mode api, explicitly RGBA' )
+        data = csrf.get_data_as_rgba()
+        data = str(data) # there's one copy
+        format = 'RGBA'
+    width, height = csrf.get_width(),csrf.get_height()
+
+    try:
+        log.info( 'Format = %s', format )
+        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
+
+if __name__ == "__main__":
+    import unittest
+    logging.basicConfig()
+    class Tests( unittest.TestCase ):
+        def test_colours( self ):
+            """Test that colours are correctly translated
+            
+            If we draw a given colour in cairo, we want the same
+            colour to show up in Pygame, let's test that...
+            """
+            for sourceColour in [
+                (255,0,0, 255),
+                (0,255,0, 255),
+                (0,0,255, 255),
+                (255,255,0, 255),
+                (0,255,255,255),
+                (255,0,255,255),
+            ]:
+                csrf,cctx = newContext( 1,1 )
+                background = mangle_color( sourceColour )
+                cctx.set_source_rgba(*background)
+                cctx.paint()
+                img = asImage( csrf )
+                colour = img.get_at( (0,0))
+                assert colour == sourceColour, (sourceColour,mangle_color(sourceColour),colour)
+    unittest.main()