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[Imgcif-l] Update: Possible bug in cbf_byte_offset.c
- To: imgcif-l@iucr.org
- Subject: [Imgcif-l] Update: Possible bug in cbf_byte_offset.c
- From: "Herbert J. Bernstein" <yaya@bernstein-plus-sons.com>
- Date: Sun, 21 Feb 2010 12:37:21 -0500
- In-Reply-To: <4B7D3610020000C80005E79E@hermes.dowling.edu>
- References: <4B7D3610020000C80005E79E@hermes.dowling.edu>
Dear Colleagues, There is a difficult to provoke bug in the CBFlib byte offset code. It arises in handling 16 bit images (not 32 bit images) in which the difference between two adjacent pixel values is -32768. I hope to have a fully tested update later this coming week. The problem is that the 16-bit code did not catch a delta of 0x8000 and escape it. I do not think you will see anything equivalent to this for 31-bit images (e.g. from the Pilatus 6M), even when there is an abrupt transition in pixel values, but I am rechecking that code and adding test cases just to be certain. Our thanks for Nick Sauter for starting us on tracing this bug. Regards, Herbert At 12:44 PM -0500 2/18/10, Herbert J. Bernstein wrote: >To: imgcif-l@iucr.org >From: "Herbert J. Bernstein" <yaya@bernstein-plus-sons.com> >Subject: Re: [Imgcif-l] Fwd: Re: Possible bug in cbf_byte_offset.c > >Dear Graeme, > > Yup. I agree. I am working on a see-saw image to cover a very >wide range of >both positive and negative delta's tp try to flush out any other such >bugs. I would appreciate your 128x128, but I also want to do a much >larger one to catch the 32 bit image cases. > > Regards, > Herbert >At 11:06 AM -0500 2/18/10, Herbert J. Bernstein wrote: > >To: <imgcif-l@iucr.org>, <nksauter@lbl.gov> > >Subject: Re: [Imgcif-l] Possible bug in cbf_byte_offset.c > > >>Dear Herbert, >> >>Surely it would be relatively straightforward to "fake" some >>pathalogical images for the purposes of testing, i.e. set values of >>0xffff, 0x0000, 0xffff, 0x0000 &c. in a "C" array and compress this to a >>CBF stream? >> >>As you could have a valid CBF 128 x 128 pixels (say) it needn't be that >>large even... If I get a quiet moment I'll code something up. >> >>Best wishes, >> >>Graeme >> >>-----Original Message----- >>From: imgcif-l-bounces@iucr.org [mailto:imgcif-l-bounces@iucr.org] On >>Behalf Of Herbert J. Bernstein >>Sent: 18 February 2010 04:21 >>To: Nicholas K. Sauter >>Cc: imgcif-l@iucr.org >>Subject: Re: [Imgcif-l] Possible bug in cbf_byte_offset.c >> >>Dear Nick, >> >> You are absolutely right. I am also having trouble working up a test >>case. It needs an image with a very large negative delta. I'll try >>to force something. >> >> In the meantime, I have updated the sourceforge cbflib svn with the >>fix in CBFlib_bleeding_edge. After I have a test case, I'll propagate >>the change more widely. >> >> I am copying this to the imgCIF list to warn others in the meantime. >> >> Thank you very much. Well done. >> >> Regards, >> Herbert >> >> >> >> >>At 11:06 AM -0800 2/17/10, Nicholas K. Sauter wrote: >>>Herbert, >>> >>>Please see line 1166 in src/cbf_byte_offset.c. >>> >>>Based on the logic of the algorithm I think this line should be >>> >>>if (delta[0] & 0x8000) { >>> >>>i.e., there is an extra "0" in the hex value in the CVS code. >>>That being said, I don't think this line has an effect on any of my >>>test cases, so I'm at a loss about how to test this out. >>> >>>Nick >> >> >>-- >>===================================================== >> Herbert J. Bernstein, Professor of Computer Science >> Dowling College, Kramer Science Center, KSC 121 >> Idle Hour Blvd, Oakdale, NY, 11769 >> >> +1-631-244-3035 >> yaya@dowling.edu >>===================================================== >>_______________________________________________ >>imgcif-l mailing list >>imgcif-l@iucr.org >>http://scripts.iucr.org/mailman/listinfo/imgcif-l >> >>-- >>This e-mail and any attachments may contain confidential, copyright >>and or privileged material, and are for the use of the intended >>addressee only. If you are not the intended addressee or an >>authorised recipient of the addressee please notify us of receipt by >>returning the e-mail and do not use, copy, retain, distribute or >>disclose the information in or attached to the e-mail. > >Any opinions expressed within this e-mail are those of the >>individual and not necessarily of Diamond Light Source Ltd. >>Diamond Light Source Ltd. cannot guarantee that this e-mail or any >>attachments are free from viruses and we cannot accept liability for >>any damage which you may sustain as a result of software viruses >>which may be transmitted in or with the message. >>Diamond Light Source Limited (company no. 4375679). Registered in >>England and Wales with its registered office at Diamond House, >>Harwell Science and Innovation Campus, Didcot, Oxfordshire, OX11 >>0DE, United Kingdom >> >> >> >> >>_______________________________________________ >>imgcif-l mailing list >>imgcif-l@iucr.org >>http://scripts.iucr.org/mailman/listinfo/imgcif-l > > >-- >===================================================== > Herbert J. Bernstein, Professor of Computer Science > Dowling College, Kramer Science Center, KSC 121 > Idle Hour Blvd, Oakdale, NY, 11769 > > +1-631-244-3035 > yaya@dowling.edu >===================================================== >_______________________________________________ >imgcif-l mailing list >imgcif-l@iucr.org >http://scripts.iucr.org/mailman/listinfo/imgcif-l -- ===================================================== Herbert J. Bernstein, Professor of Computer Science Dowling College, Kramer Science Center, KSC 121 Idle Hour Blvd, Oakdale, NY, 11769 +1-631-244-3035 yaya@dowling.edu ===================================================== _______________________________________________ imgcif-l mailing list imgcif-l@iucr.org http://scripts.iucr.org/mailman/listinfo/imgcif-l
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