1 files changed, 69 insertions, 0 deletions
diff --git a/olpcgames/_cairoimage.py b/olpcgames/_cairoimage.py
new file mode 100644
index 0000000..30e53f0
--- /dev/null
+++ b/olpcgames/_cairoimage.py
@@ -0,0 +1,69 @@
+"""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