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handling of compressed images


 
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Voerman, L.
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PostPosted: Thu Mar 17, 2016 10:37 am    Post subject:
handling of compressed images
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Hi Robert,


I have written a few improvements for the osg's handling of compressed images; adding options 
- to copy subimages of compressed textures if region is a mutiple of block size,
- recognize GL_KHR_texture_compression_astc_hdr formats of compressed images
- get pixels from dxtc compressed textures
- (lossless) rotate dxtc comperssed textures
- actualy test pixels in dxt3/dxt5 files for opacity
- strip dxt3/dxt5 blocks of alpha channels 




attached is a zip with modified versions of
include/osg/Image
src/osg/Image.cpp
src/osg/ImageUtils.cpp
src/osg/dxtctool.cpp
src/osg/dxtctool.h


Changes are relative to current Git master branch.


Regards, Laurens.

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PostPosted: Thu Mar 17, 2016 10:58 am    Post subject:
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Hi Laurens,

Great changes, sounds like very useful features. Though, perhaps the addition to "get pixels from dxtc compressed textures", if it is what I think it is, should wait until the S3TC patent expires? http://www.patentcountdown.org/
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Voerman, L.
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PostPosted: Thu Mar 17, 2016 12:37 pm    Post subject:
handling of compressed images
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Hi Jannik,

thanks for your question, basically I have no idea what the answer should be. The rotate block and retrieve value functions do interpret the content of the compressed blocks, and therefore might be prohibited.
Any advise on the legality would be appreciated, as I cannot fully understand a patent covering the possibility to decode an image.
Even though I wrote the code based on publicy available descriptions of the format, I forgot that the format itself could be patented.
I do not intend to expose all osg users to patent fee claims - so the implementation might need to be disabled until the patent expires, the page you link says: Estimated expiry: Oct 2, 2017


Regards, Laurens.


ps. 
1> I suppose copying compressed blocks alligned to it's footprint should be fine, as the content of the block is not interpreted and the idea of grouping compressed pixels in blocks is not patented.


2> would an conditional compile like
#ifdef THIS_PATENT_HAS_EXPIRED
    be sufficient to protect the osg community against claims? 
    the most convenient place to store the code for me is still in the osg repository, and it might be usefull to describe the reason for not compiling it into the osg.






On Thu, Mar 17, 2016 at 11:58 AM, Jannik Heller < (
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Quote:
Hi Laurens,

Great changes, sounds like very useful features. Though, perhaps the addition to "get pixels from dxtc compressed textures", if it is what I think it is, should wait until the S3TC patent expires? http://www.patentcountdown.org/

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PostPosted: Mon Oct 02, 2017 12:44 pm    Post subject:
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Hi Laurens,

FYI, the S3TC patent appears to have expired now [1]. Maybe you're interested in picking up this submission again and re-submitting on github?

http://www.patentcountdown.org/
https://www.phoronix.com/scan.php?page=news_item&px=S3TC-Patent-Expires-Next-Week
https://www.phoronix.com/scan.php?page=news_item&px=S3TC-For-Mesa-Finally

Cheers,
Jannik
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psi29a
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PostPosted: Tue Oct 03, 2017 12:15 pm    Post subject:
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I second this. it would be great to see this included now that the patent has expired.

Cheers,
bret
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