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Re: NSImageView Will Not Alias Images
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Re: NSImageView Will Not Alias Images


  • Subject: Re: NSImageView Will Not Alias Images
  • From: Laurent Daudelin <email@hidden>
  • Date: Tue, 6 Apr 2010 17:40:18 -0700

On Apr 6, 2010, at 17:24, Chris Tracewell wrote:

> On Apr 6, 2010, at 4:50 PM, Ken Ferry wrote:
>
>>
>> On Tue, Apr 6, 2010 at 2:58 PM, Jens Alfke <email@hidden> wrote:
>>
>> On Apr 6, 2010, at 1:17 PM, Chris Tracewell wrote:
>>
>> I am trying to get NSImageView to alias dropped images, but it refuses.
>>
>> Nitpick: you mean "antialias". Aliasing is what creates the jaggies, antialiasing smooths them away.
>>
>>
>> Just spent an hour looking and trying several variations to no avail. Here's what I have done in a subclass of NSImageView.
>>
>> I remember having to deal with this too, years ago. It's too bad AppKit hasn't added support for this yet :(
>>
>> The problem is that NSImageView internally keeps a scaled copy of the image. So the actual scaling that creates the aliasing isn't done in the drawRect: method at all.
>>
>> This was once true, but is out of date.  I'd like to see a test app.  For example, how do you know you aren't getting antialiasing?  It may be that you just don't like the output. :-)
>
> Well - NSImageInterpolationHigh and NSImageInterpolationNone produce the same exact result - screen shot copy (control-command-shift-4) the imageView built once using NSImageInterpolationHigh  and once using NSImageInterpolationNone then paste each into a Photoshop layer, align them perfectly and then turn the top layer off and on at 800% and there is not a single pixel that moves or changes color.
>
> The dropped image is roughly 1000 x 1000 (a screen shot PNG) and the imageView size is 200x200
>
> To make sure the currentContext was correct - I log [[NSGraphicsContext currentContext] imageInterpolation] for each build and it shows the correct values 3 and 1 respectively. And then just to be super sure I I log [[NSGraphicsContext currentContext] isDrawingToScreen] inside drawRect of my NSImageView subclass and get YES.
>
> I did implement my own image sizing in drawRect and then used [self setImage] and it works great. Not sure what could be the issue.

Funny you're mentioning this problem as I've been trying to get a thumbnail icon of a pdf document and I get pretty much the same results. It doesn't seem to matter whether I use NSInterpolationHigh or NSInterpolationNone, at least I couldn't see any difference in the resulting image in Preview even when magnified.

-Laurent.
--
Laurent Daudelin
AIM/iChat/Skype:LaurentDaudelin 				http://nemesys.dyndns.org
Logiciels Nemesys Software              				email@hidden
Photo Gallery Store: http://laurentdaudelin.shutterbugstorefront.com/g/galleries

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References: 
 >NSImageView Will Not Alias Images (From: Chris Tracewell <email@hidden>)
 >Re: NSImageView Will Not Alias Images (From: Jens Alfke <email@hidden>)
 >Re: NSImageView Will Not Alias Images (From: Ken Ferry <email@hidden>)
 >Re: NSImageView Will Not Alias Images (From: Chris Tracewell <email@hidden>)

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