[cairo] High Quality ImagePattern Scaling

[Andrew Ingram]

Hi all,

Having explored other options i've come to try using pycairo to resize 
and rotate some png images. The problem i'm having is that no matter 
what options I specify, I can't seem to get the resized images to be of 
a high quality, the output is very pixelated even without rotating.

This is my algorithm:

image = cairo.ImageSurface.create_from_png(path)
   
# some mathsy calculations
   
pattern = cairo.SurfacePattern(image)
pattern.set_filter(cairo.FILTER_BEST)
   
surface = cairo.ImageSurface(cairo.FORMAT_ARGB32, WIDTH, HEIGHT)
context = cairo.Context(surface)
   
context.set_antialias(cairo.ANTIALIAS_SUBPIXEL)

context.rectangle (0,0,WIDTH,HEIGHT)
context.translate(H_SHIFT,V_SHIFT)
context.scale(scaleX,scaleY)  
context.rotate(math.radians(float(rotate)))

context.set_source(pattern)
context.fill()
   
output = cStringIO.StringIO()
surface.write_to_png(output)


I've tried using PIL to achieve this but the quality for rotations was 
very poor, cairo seems to do rotations to a reasonable quality but 
resizing is a different matter.

Regards,
Andrew Ingram

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