Re: Image scaling
Re: Image scaling
- Subject: Re: Image scaling
- From: John Stiles <email@hidden>
- Date: Fri, 04 Jan 2008 15:51:02 -0800
I'd suggest that if you are trying to demonstrate an image's sharpness,
a lossy format like JPG is not the format to use :)
FWIW it's entirely possible that Flickr is explicitly running a
sharpening filter on the image before scaling it down. I am not 100%
sure but I am fairly positive that Google's photo service (Picasa) does
this when you scale down images from within its iPhoto plugin.
Adam Knight wrote:
On Jan 4, 2008, at 4:25 PM, Adam Knight wrote:
I tried this using CIImage and a CILanczosScaleTransform filter then
using NSBitmapImageRep's initWithCIImage method. This worked very
well and made a great image, but it looks like Apple's
initWithCIImage code leaks a whole copy of the image outside of my
reach. I'm working with too many images for this to be good. Also,
this method drops the file metadata entirely (EXIF, etc.) and doesn't
appear to give me the chance to add it back in.
I take this back -- even this method produces slightly blurry scaled
images. Is there anything in the system that can make a sharp, proper
scaled image?
Examples:
http://www.bssware.com/~ahknight/good_scale.jpg (Image uploaded to
Flickr in full size, the resulting image at 500px wide)
http://www.bssware.com/~ahknight/bad_scale.jpg (Scaled using
either CG or CI to 500 pixels wide)
Adam Knight
Co-Founder; CTO
Barton Springs Software
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