[GREENFOOT-94] Scaling transparent GreenfootImages is buggy on Leopard

If you scale a GreenfootImage on Leopard when using the Quarts rendering pipeline the images are no longer transparent. They produce some weird colors when painted on top of other colors \- possibly using an XOR algorithm or something similar.

This can be seen in the explosion in the lunarlander scenario.

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Issue metadata

• Issue type: Bug
• Priority: Medium
• Fix versions: 1.4.0