On 6 Mar 2012, at 1:21 AM, Graham Cox wrote:
> Why not add a single layer with red on the left, alpha = 1, and blue on the
> right, alpha = 1? I don't see why you need to composite two layers.
>
> Drawing a gradient dynamically is probably more efficient than blitting a
> PNG, and will be resolution independent.
My experience on iOS is that compositing of any kind, at least offscreen, is
very expensive, even with no scaling. That includes gradients and shadows. I
profile, and fall back on PNG if necessary.
Also, you'd have better control over how the gradient looks. Trusting Core
Graphics may not get you what you want.
If we're talking about a background for an iPhone, or even of the right-hand
portion of a UISplitView, the size and load time aren't an issue. (I've had to
use a 1600 x 1600, though, for which the preheat time is half a second; doing
-[UIImage imageWithContentsOfFile:] at startup didn't help.)
If the compositing is being done on a Mac, then never mind — most Macs have CPU
and GPU to spare.
— F
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