I have read many of the posts on this, and I ended up using this code:
NSSize theNewSize = {width*scaleFactor, height*scaleFactor};
NSImage *resizedImage = [[NSImage alloc] initWithSize: theNewSize];
[resizedImage lockFocus];
[NSGraphicsContext saveGraphicsState];
[[NSGraphicsContext currentContext]
setImageInterpolation:NSImageInterpolationHigh];
[image drawInRect:NSMakeRect(0.0,0.0,theNewSize.width,
theNewSize.height) fromRect:NSMakeRect(0.0,0.0,[image size].width,
[image size].height) operation:NSCompositeCopy fraction:1.0];
[NSGraphicsContext restoreGraphicsState];
It has a very poor interpolation, whether I use
NSImageInterpolationHigh, Low, or no call at all. "None" does cause
the image to not interpolate, as expected.
I am drawing to an offscreen bitmap, and using:
[image addRepresentation:offscreenRep];
prior to these calls.
In contrast, if the Java app call below is used, the image looks great:
g.setRenderingHint(RenderingHints.KEY_INTERPOLATION,
RenderingHints.VALUE_INTERPOLATION_BILINEAR);
Since this Java code runs well on my Mac (Leopard), I assume Java uses
low level system calls mapped to its functions. I would expect NSImage
to be similar in quality.
I am new to Obj C, so I apologize if I am missing something here.
I am thinking something is wrong with the call since Preview does no
better job scaling than my Cocoa code does.
Also, ImageApp code example also has a similar call, and setting the
quality high or low again has no effect.
http://developer.apple.com/samplecode/ImageApp/index.html
Here is a link to a forum that has the images in comparison:
http://episteme.arstechnica.com/eve/forums?a=tpc&s=50009562&f=6330927813&m=430008360931&r=430008360931#430008360931
If it will work better, how do I call the interpolation correctly?
Thanks in advance for any help!
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