Re: Anti-alias an NSIamgeView
Re: Anti-alias an NSIamgeView
- Subject: Re: Anti-alias an NSIamgeView
- From: Ben Mackin <email@hidden>
- Date: Sun, 24 Nov 2002 18:26:08 -0800
On 11/24/02 6:12 PM, "Dennis De Mars" <email@hidden> wrote:
>
Anti-aliasing is the process of preventing "aliasing" artifacts when a
>
signal is sampled. For an image, this means that if you have an image
>
at a high resolution, you pass it through an anti-alias filter before
>
sampling down to a lower resolution.
Before, I was displaying my images at 72 DPI (by accident they should have
been 209) and I could see that it was "blurring" the image, and it looked
pretty bad. I hope that isn't the best Quartz can do...
>
For geometric shapes (lines, bezier curves) and fonts which are defined
>
in terms of bezier curves, the resolution of the image before rendering
>
is effectively infinite. The standard way to apply anti-aliasing is to
>
render these objects at a high resolution (that is, at some multiple of
>
the pixels you actually need) and then apply an anti-aliasing filter
>
when downsampling to the actual resolution desired. That is what Quartz
>
does when you draw shapes and character strings into a view.
>
>
For predefined bitmap images, there is nothing Quartz can do if the
>
image is already at the size needed. If the predefined image is larger
>
than what you require, Quartz will apply anti-aliasing while scaling
>
down the image to the size requested. For instance, all of those images
>
you see in the dock are derived from a large icon which is scaled down
>
and looks smooth at any size, but to do this Quartz needs a large image
>
to begin with. If not, the results do not look good.
I guess I should have been a little clearer. The image is filled with text
(it is a received fax). So the image received is a TIFF file at 209 DPI,
filled with text (and some "true" images).
What I am shooting for is the look of Preview. If I open my tiff file in
Preview it anti-aliases it (if I turn off anti-aliasing in Preview it
degrades the quality so I know something is happening). So there has got to
be some way of keeping my DPI, and getting the anti-aliasing to work,
because that9s what preview seems to be able to do.
Thanks,
Ben
http://www.shayufilms.com
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