Re: can a Cocoa app scale jpeg images as nicely as Preview does?
Re: can a Cocoa app scale jpeg images as nicely as Preview does?
- Subject: Re: can a Cocoa app scale jpeg images as nicely as Preview does?
- From: Mike Morton <email@hidden>
- Date: Fri, 7 Oct 2005 12:30:25 -0400
Ali et alia --
This worked great.
Googling for setImageInterpolation:, I found
<http://www.cocoadev.com/index.pl?ThumbnailImages>. Of the techniques
there, I found that I had to use drawInRect:... -- compositing didn’t
work for me.
I wound up doing:
NSImage *result = [[[NSImage alloc] initWithSize: newSize]
autorelease];
[result lockFocus];
[[NSGraphicsContext currentContext] setImageInterpolation:
quality];
[self drawInRect: NSMakeRect (0, 0, newSize.width,
newSize.height)
fromRect: NSMakeRect (0, 0, currentSize.width,
currentSize.height)
operation: NSCompositeCopy
fraction: 1.0];
[result unlockFocus];
Thanks!
-- Mike
On Oct 6, 2005, at 4:02 PM, Ali Ozer wrote:
You can get better scaling via -[NSGraphicsContext
setImageInterpolation:NSImageInterpolationHigh].
Ali
Begin forwarded message:
From: Mike Morton <email@hidden>
Date: October 6, 2005 9:34:33 AM PDT
To: Cocoa-Dev <email@hidden>
Subject: can a Cocoa app scale jpeg images as nicely as Preview does?
Folks --
When I load a jpeg image into my app and shrink it, certain images
look pretty awful. When I open the same image in Preview and Zoom Out
a bunch of times, it briefly looks awful, but then it sharpens up and
looks great.
For example, try grabbing
<http://images.amazon.com/images/P/B000006TRV.01._SCLZZZZZZZ_.jpg>
and doing Zoom Out six times, scaling it down 8x in each dimension.
You can almost read the text.
When I scale that image by the same amount in a simple Cocoa app (by
resizing the NSImage or by making the NSImageView the right size), it
comes out pretty ugly
I’m sure there are techniques and libraries out there to do this, but
I thought NSImage would do a good job right out of the box...
Thanks,
-- Mike
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