Re: Core Graphics: Is it better to up-sample or down-sample images when drawing into a rect?
Re: Core Graphics: Is it better to up-sample or down-sample images when drawing into a rect?
- Subject: Re: Core Graphics: Is it better to up-sample or down-sample images when drawing into a rect?
- From: Steve Christensen <email@hidden>
- Date: Thu, 25 Aug 2016 06:20:37 -0700
> On Aug 24, 2016, at 8:37 PM, Jeff Szuhay <email@hidden> wrote:
>
>
>> On Aug 24, 2016, at 8:02 PM, Britt Durbrow <email@hidden> wrote:
>>
>>
>>> On Aug 24, 2016, at 12:59 PM, Jeff Szuhay <email@hidden> wrote:
>>>
>>> I draw my images (clocks) into a “reference” sized rectangle—for simplified position calculations—and then have CoreGraphics scale into the destination view rect.
>>
>> Don’t do that with bitmap scaling. It’s wasteful, and will look bad.
>>
>> Instead, create the bitmap at the correct size for it’s destination; and use the drawing matrix transform functions (scale, translate, rotate, etc) to set up your drawing environment.
>
>
> Okay, so when the user changes the clock size (it’s destination), then recreate the bitmap to the new size and redraw everything at the new scale?
Yep. That way you get the best-quality image since it's built to fit an explicit size.
And if parts of your display are cacheable, e.g., the clock background, then you can recreate them at that point. Keep an ivar with the size of the view when the image(s) were last cached and compare it against the view's current size.
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