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  #1  
Old June 14th 13, 11:19 PM posted to rec.photo.digital
Dudley Hanks[_4_]
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Posts: 1,282
Default Crazy Comp...

Two files compressed from an original with 16,777,216 pixels and 16,777,216
colours...

One is a .png file, 133,450 bites...
http://www.blind-apertures.ca/pics/16MillionColours.png

The other is a .jpg, 7,416,217 bytes...
http://www.blind-apertures.ca/pics/16MillionColours.jpg

Which one has lost about 3/4 of the original data?

Take Care,
Dudley

  #2  
Old June 15th 13, 07:34 AM posted to rec.photo.digital
David Taylor
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Posts: 1,146
Default Crazy Comp...

On 14/06/2013 23:19, Dudley Hanks wrote:
Two files compressed from an original with 16,777,216 pixels and
16,777,216 colours...

One is a .png file, 133,450 bites...
http://www.blind-apertures.ca/pics/16MillionColours.png

The other is a .jpg, 7,416,217 bytes...
http://www.blind-apertures.ca/pics/16MillionColours.jpg

Which one has lost about 3/4 of the original data?

Take Care,
Dudley


The JPEG reports just under 4 million colours. Wonderful what lossless
compression can achieve on specially contrived data!

Visually indistinguishable, at a quick glance.
--
Cheers,
David
Web: http://www.satsignal.eu
  #3  
Old June 15th 13, 10:41 AM posted to rec.photo.digital
Pablo
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Posts: 220
Default Crazy Comp...

Dudley Hanks wrote:

Two files compressed from an original with 16,777,216 pixels and
16,777,216 colours...

One is a .png file, 133,450 bites...
http://www.blind-apertures.ca/pics/16MillionColours.png

The other is a .jpg, 7,416,217 bytes...
http://www.blind-apertures.ca/pics/16MillionColours.jpg


"socket timed out"

--

Pablo

http://www.ipernity.com/home/313627
http://paulc.es/

  #4  
Old June 17th 13, 02:53 PM posted to rec.photo.digital
Martin Brown
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Posts: 821
Default Crazy Comp...

On 14/06/2013 23:19, Dudley Hanks wrote:
Two files compressed from an original with 16,777,216 pixels and
16,777,216 colours...

One is a .png file, 133,450 bites...
http://www.blind-apertures.ca/pics/16MillionColours.png

The other is a .jpg, 7,416,217 bytes...
http://www.blind-apertures.ca/pics/16MillionColours.jpg

Which one has lost about 3/4 of the original data?


Considering that the target image is inappropriate for JPEG encoding it
has actually done well to achieve a fairly close visual similarity.

Photoshop isn't the best at this by any means. PSPro JPEG manages

5,502,195 bytes and 4007721 colours as a JPEG

and

1,754,469 bytes and 16,377,913 colours as a J2k (lossy)

Moral of the story you need to think about which method of compression
you use on line art and test pieces intended to break JPEG encoders.

--
Regards,
Martin Brown
 




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