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#41
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'extra' lossless compression for camera raw images
"Paul Furman" wrote in message . .. Sachin Garg wrote: "ray" wrote in message ... On Thu, 20 Mar 2008 09:40:05 +0530, Sachin Garg wrote: "ray" wrote in message ... On Thu, 20 Mar 2008 08:52:46 +0530, Sachin Garg wrote: "ray" wrote in message ... On Wed, 19 Mar 2008 18:08:26 -0400, me wrote: On 19 Mar 2008 21:49:36 GMT, in rec.photo.digital ray wrote: I'd be happy to do that if you'd provide specific information on a couple of images. Looking at the bar graphs is really not suitable. The bar graphs are for the images he provides on the site. Understood. And I'd be happy to use several compression programs to do the same ones - if I had any results to compare to. BTW - I've just done a simple bzip2 compression on a Kodak P850 raw file - compressed size is 53% of uncompressed. Thats great. If even bzip2 is able to get 53%, it will be very interesting to see how much better sgraw will be. Yes, it certainly would. It gives "Error: unsupported file format" - bzip2 works properly. Yep, for now sgraw only supports Nikon and Fuji raw formats. I will definitely try to support kodak formats in future, but for now they are unsupported. Really. I would have thought you would have started with DNG - it is quite well documented. Yep, its documented and I have tried (with partial success till now). Problem is that as DNG files need to support raw files from all cameras, there are lots of minor camera-specific variations in it depending on which orginal raw format a DNG was created from (a reason why editing softwares aren't always able to support DNGs from cameras they don't support natively). So supporting all DNGs will mean supporting all those variations. Now these are 'small' variations, nothing too difficult, but will need cosiderable time and effort due to huge no. of cameras. Get some programmers working on it, pay them with licensing fees from Adobe grin. LOL Seriously, I convert to dng & would like this but I'm not going to archive my photos in an obscure third party format. Yes, thats understandable. It might help a little to consider that conversion with sgraw is two-way. We will always be able to convert back to original formats, so there will be "no vendor lock-in" which is what usually makes obscure 3rd party formats ugly. If it can be done fast on-camera, the camera manufacturers could use it. Its fast, but looking at what camera makers use right now, and the speed expectation from cameras (multiple shots per second), it will probably be a little while before this can be seen in camera (and thats just the technical side of trouble). Sachin Garg [India] www.sachingarg.com | www.imagecompression.info |
#42
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'extra' lossless compression for camera raw images
On 19 Mar 2008 16:47:38 GMT, ray wrote:
On Wed, 19 Mar 2008 01:28:47 +0530, Sachin Garg wrote: I just finished writing a small tool (sgraw) which can losslessly compress camera raw images, usually between 20-to-60%. (Regulars here might recall I have mentioned this 'possibility' earlier, I finally put in some hours to actually build a working demo :-) http://www.sachingarg.com/compression/sgraw/ That would be savings between 1GB to 3GB for every 5GB of data. Even when camera has already compressed the raw image (which isn't always the case), its still possible to squeeze out extra compression as cameras have to use simple algorithms for speed. Compression is totally lossless, we get back the exact file we start with (just like with zip), so both pixel information and meta-data are perfectly restored. This is just the first quick hack version (and supports all nikon and fuji cameras), so it obviously wouldn't make sense to actually use it for backups etc, but if there is enough interest I can build it further to support other raw formats, along with improved compression and speed. Your thoughts on this? Sachin Garg [India] www.sachingarg.com | www.imagecompression.info It seems totally superfluous since there are already dozens of compression programs available. What makes you think you've discovered some 'new and improved' algorithm? Agreed. I just used WinRAR on a couple of RAW files and got anywhere from 38% to 52% compression rates by just using its auto defaults. RAR is a well-known and universal compression method that works well for all multimedia formats. Unless you can consistently do greater than 50-60% on all RAW files it's not worth anyone's time to test this for you. Well, except as your own as a learning exercise and a way to get attention for wasting everyone else's time and resources in doing so. |
#43
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'extra' lossless compression for camera raw images
"KandorMan" wrote in message ... On 19 Mar 2008 16:47:38 GMT, ray wrote: On Wed, 19 Mar 2008 01:28:47 +0530, Sachin Garg wrote: I just finished writing a small tool (sgraw) which can losslessly compress camera raw images, usually between 20-to-60%. (Regulars here might recall I have mentioned this 'possibility' earlier, I finally put in some hours to actually build a working demo :-) http://www.sachingarg.com/compression/sgraw/ That would be savings between 1GB to 3GB for every 5GB of data. Even when camera has already compressed the raw image (which isn't always the case), its still possible to squeeze out extra compression as cameras have to use simple algorithms for speed. Compression is totally lossless, we get back the exact file we start with (just like with zip), so both pixel information and meta-data are perfectly restored. This is just the first quick hack version (and supports all nikon and fuji cameras), so it obviously wouldn't make sense to actually use it for backups etc, but if there is enough interest I can build it further to support other raw formats, along with improved compression and speed. Your thoughts on this? It seems totally superfluous since there are already dozens of compression programs available. What makes you think you've discovered some 'new and improved' algorithm? Agreed. I just used WinRAR on a couple of RAW files and got anywhere from 38% to 52% compression rates by just using its auto defaults. RAR is a well-known and universal compression method that works well for all multimedia formats. Yes, general purpose compressors like rar/bzip2/zip etc can give good results if original raw format did not use any compression (lossless). sgraw is tuned for raw images, so it can give consistently better results than them (theoritically at better speed too, but current implementation is slow. I will try to improve this). Besides, it can further compress the raw files even if they were already compressed. Compression ratio is relatively less in this case as there are technical limitations. I would love to see any results different from what I found in my testing. Which camera's raw files did you use for your tests? If these were from a Nikon or Fuji, I am hoping that you will be amazed to see the difference when using sgraw. If it was some other camera then we will have to wait till I can work on those formats. Unless you can consistently do greater than 50-60% on all RAW files it's not worth anyone's time to test this for you. Well, except as your own as a learning exercise and a way to get attention for wasting everyone else's time and resources in doing so. Fortunately, not everyone uses 'all' the cameras :-) If its getting results on your raw files which are good enough for you, I will be happy to know that you can find it useful. Otherwise, my apologies for wasting your time. (If rar is getting those results you mentioned on your raw files, I am very optimistic that you will like what sgraw will manage to do for you :-) Sachin Garg [India] www.sachingarg.com | www.imagecompression.info |
#44
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'extra' lossless compression for camera raw images
On Mon, 24 Mar 2008 10:13:05 +0530, Sachin Garg wrote:
"KandorMan" wrote in message ... On 19 Mar 2008 16:47:38 GMT, ray wrote: On Wed, 19 Mar 2008 01:28:47 +0530, Sachin Garg wrote: I just finished writing a small tool (sgraw) which can losslessly compress camera raw images, usually between 20-to-60%. (Regulars here might recall I have mentioned this 'possibility' earlier, I finally put in some hours to actually build a working demo :-) http://www.sachingarg.com/compression/sgraw/ That would be savings between 1GB to 3GB for every 5GB of data. Even when camera has already compressed the raw image (which isn't always the case), its still possible to squeeze out extra compression as cameras have to use simple algorithms for speed. Compression is totally lossless, we get back the exact file we start with (just like with zip), so both pixel information and meta-data are perfectly restored. This is just the first quick hack version (and supports all nikon and fuji cameras), so it obviously wouldn't make sense to actually use it for backups etc, but if there is enough interest I can build it further to support other raw formats, along with improved compression and speed. Your thoughts on this? It seems totally superfluous since there are already dozens of compression programs available. What makes you think you've discovered some 'new and improved' algorithm? Agreed. I just used WinRAR on a couple of RAW files and got anywhere from 38% to 52% compression rates by just using its auto defaults. RAR is a well-known and universal compression method that works well for all multimedia formats. Yes, general purpose compressors like rar/bzip2/zip etc can give good results if original raw format did not use any compression (lossless). sgraw is tuned for raw images, so it can give consistently better results than them (theoritically at better speed too, but current implementation is slow. I will try to improve this). Besides, it can further compress the raw files even if they were already compressed. Compression ratio is relatively less in this case as there are technical limitations. I would love to see any results different from what I found in my testing. Which camera's raw files did you use for your tests? If these were from a Nikon or Fuji, I am hoping that you will be amazed to see the difference when using sgraw. If it was some other camera then we will have to wait till I can work on those formats. Unless you can consistently do greater than 50-60% on all RAW files it's not worth anyone's time to test this for you. Well, except as your own as a learning exercise and a way to get attention for wasting everyone else's time and resources in doing so. Fortunately, not everyone uses 'all' the cameras :-) If its getting results on your raw files which are good enough for you, I will be happy to know that you can find it useful. Otherwise, my apologies for wasting your time. (If rar is getting those results you mentioned on your raw files, I am very optimistic that you will like what sgraw will manage to do for you :-) Sachin Garg [India] www.sachingarg.com | www.imagecompression.info Actually, I have found that converting to DNG does quite well. And, of course, DNG is supported already by photo editors, so no need to convert back. |
#45
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'extra' lossless compression for camera raw images
On Mon, 24 Mar 2008 16:31:25 -0400, me wrote:
On 24 Mar 2008 16:02:42 GMT, in rec.photo.digital ray wrote: Actually, I have found that converting to DNG does quite well. And, of course, DNG is supported already by photo editors, so no need to convert back. You can't, as DNG doesn't preserve 100% of the metadata. Of course I can. |
#47
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'extra' lossless compression for camera raw images
On Mon, 24 Mar 2008 19:15:29 -0400, me wrote:
On 24 Mar 2008 22:38:33 GMT, in rec.photo.digital ray wrote: On Mon, 24 Mar 2008 16:31:25 -0400, me wrote: On 24 Mar 2008 16:02:42 GMT, in rec.photo.digital ray wrote: Actually, I have found that converting to DNG does quite well. And, of course, DNG is supported already by photo editors, so no need to convert back. You can't, as DNG doesn't preserve 100% of the metadata. Of course I can. Not according to Adobe in: Introducing the Digital Negative specification: Information for Manufacturers: http://www.adobe.com/products/dng/pd...ufacturers.pdf "It should be noted that the Adobe DNG Converter will not necessarily maintain all of the private metadata in certain camera-specific raw formats because this information is not publicly documented and therefore not available to Adobe. However, the Adobe DNG Converter will maintain all of the original image data as well as all of the metadata needed for a high-quality final conversion. Arguably, the private metadata is not really archival, regardless of the format used, simply because it is undocumented. Nevertheless, Adobe recommends that, when photographers use the Adobe DNG Converter for archival purposes, they should maintain both the resulting DNG file and the original camera-specific file." That's fine, but I can still use it if I damned well please!! |
#48
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'extra' lossless compression for camera raw images
["Followup-To:" header set to rec.photo.digital.slr-systems.]
John McWilliams wrote: You can't, as DNG doesn't preserve 100% of the metadata. [...] Note the words "not necessarily maintain....", certainly leaving room for some RAW formats that have all data captured regardless. True. But unless it is stated explicitely that for format X all metadata is preserved, and that is proved by experimentation ... -Wolfgang |
#49
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'extra' lossless compression for camera raw images
wrote:
On 24 Mar 2008 22:38:33 GMT, in rec.photo.digital ray wrote: On Mon, 24 Mar 2008 16:31:25 -0400, me wrote: On 24 Mar 2008 16:02:42 GMT, in rec.photo.digital ray wrote: Actually, I have found that converting to DNG does quite well. And, of course, DNG is supported already by photo editors, so no need to convert back. You can't, as DNG doesn't preserve 100% of the metadata. Of course I can. Not according to Adobe in: Introducing the Digital Negative specification: Information for Manufacturers: http://www.adobe.com/products/dng/pd...ufacturers.pdf "It should be noted that the Adobe DNG Converter will not necessarily maintain all of the private metadata in certain camera-specific raw formats because this information is not publicly documented and therefore not available to Adobe. Of course it is available: it's there in the file. Adobe's statement is disingenuous. If Adobe does not funnly understand some part of a file, they need merely copy it, as is, into their generic format along with the info needed to put it back in the original format. Doug McDonald |
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