Re: [APML] Scaling Images (was: Cocoon Nebula)

[Matt BenDaniel <matt@starmatt.com>]

At 11:08 PM 11/6/2001 -0500, Jerry Lodriguss wrote:

>>I downloaded the free evaluation version of Genuine Fractals. Using GF I scaled the image down to the exact same size (703x640) as my PS JPG and uploaded it to my web site:
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>>The pixels patterns resulting from GF are slightly different than Photoshop bicubic. The GF stars are sharper and less smeared. The JPG size of the GF image is larger, which may be an indication that GF preserves more information from the original image.
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>>It is very curious how the image annoyingly shifts around when you toggle between the two. Could PS or GF be screwing up its scaling?
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>Hi Matt,
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>I'm trying to understand exactly what you did here.
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>You took an original uncompressed full-sized image and you ran Genuine Fractals on it to compress it. Did you use the lossey or lossless compression in GF?

lossless


>Then you downsized it in GF, and you JPEG compressed it? So which image is that on your web page the img_on or img_off?

mouse off image is GF.


>You also took the original uncompressed full-sized image, and downsized it in PS, and Jpeg compressed it?

yup


>Then you compared both as PS JPEGS?
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>This sounds crazy to me. <G> The comparison should have been using both just resized and not compressed the final time. The GF image was already compressed once, then re-sized, and then compressed again (the final time with Jpeg).

The GF is compression is lossless.

BTW the same grid artifacts are apparent in PS even when JPEG is involved at all. I resize form the original without JPEG conversion. The same weird grid actions happens when I toggle the top layer. This is NOT a JPEG issue.


>To my understanding, Genuine Fractals is mainly for enlarging images larger than the original file size.
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>As for enlarging images with GF, I've done several comparisons between GF and Photoshop's interpolation when increasing the file size of an image, and I don't see where GF is any better at all.  I think Chuck has reached the same conclusions from some tests he did with Lightjet prints.

When I zoom in on the downscaled images, I see, differences. The GF image is definitely sharper with more detail visible. You can even see it in the Cocoon nebula itself on my web site.


>GF is supposed to work better with images that contain fractal patterns in them, such as nature shots with trees. I have heard that GF does work better than PS with extreme enlargements, like blowing up a 35mm original to the size of a billboard, and if I ever need to do this, I'll keep GF in mind. <G>
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>Jerry
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>Save your money and don't get GF.  Do some comparisons on enlarging an original non-compressed file both with GF and Photoshop.
>Astrophotography, Tips and Techniques
>for Digital Enhancement in Photoshop:
>http://www.astropix.com
>
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--
Matt BenDaniel
http://starmatt.com


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