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Re: Any quick, easy way to compare two images?

From john hevelin <bwotte@panix.com>
Newsgroups comp.sys.mac.system
Subject Re: Any quick, easy way to compare two images?
Date 2014-01-24 01:57 +0000
Organization PANIX Public Access Internet and UNIX, NYC
Message-ID <lbshan$kfr$1@reader1.panix.com> (permalink)
References <lbrnpr$q5o$1@dont-email.me> <230120141424174937%nospam@nospam.invalid> <lbrvrh$7ua$1@dont-email.me> <bkdesoFr87nU1@mid.individual.net> <lbscm3$7ua$3@dont-email.me>

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Don Bruder <dakidd@sonic.net> wrote:

> I think that's likely going to be the way to go - I actually get handed 
> a wad of NSData that I then feed to NSImage to create the actual image, 
> so if I save the raw data to PreviousImage, then XOR it against the 
> "NewImage" data (before feeding it to NSImage), it should be simple 
> enough. Better yet, just grab the same range of bytes from each, rather 
> than doing the full data buffer...

I know nothing about your problem domain, but if what you want to
do is compare two sets of bytes for equality, and you don't have
metadata such as timestamps, why not use cmp(1)?  It does a
byte-by-byte comparison and terminates at the first inequality.
Your worst case would be if the two sets are identical, since cmp
would read both files in their entirety.

I wouldn't use diff(1) -- diff would report all the detected
differences between the two sets, which could be considerable.

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Thread

Any quick, easy way to compare two images? Don Bruder <dakidd@sonic.net> - 2014-01-23 10:42 -0800
  Re: Any quick, easy way to compare two images? nospam <nospam@nospam.invalid> - 2014-01-23 14:24 -0500
    Re: Any quick, easy way to compare two images? Don Bruder <dakidd@sonic.net> - 2014-01-23 13:00 -0800
      Re: Any quick, easy way to compare two images? Tom Stiller <clusterfux.upmon@gmail.com> - 2014-01-23 21:11 +0000
        Re: Any quick, easy way to compare two images? Don Bruder <dakidd@sonic.net> - 2014-01-23 16:38 -0800
          Re: Any quick, easy way to compare two images? john hevelin <bwotte@panix.com> - 2014-01-24 01:57 +0000
            Re: Any quick, easy way to compare two images? Doug Anderson <ethelthelogremovethis@gmail.com> - 2014-01-23 18:03 -0800
        Re: Any quick, easy way to compare two images? Don Bruder <dakidd@sonic.net> - 2014-01-23 21:25 -0800
      Re: Any quick, easy way to compare two images? JF Mezei <jfmezei.spamnot@vaxination.ca> - 2014-01-23 16:31 -0500
        Re: Any quick, easy way to compare two images? nospam <nospam@nospam.invalid> - 2014-01-23 16:57 -0500
          Re: Any quick, easy way to compare two images? JF Mezei <jfmezei.spamnot@vaxination.ca> - 2014-01-23 17:02 -0500
        Re: Any quick, easy way to compare two images? Don Bruder <dakidd@sonic.net> - 2014-01-23 21:28 -0800
      Re: Any quick, easy way to compare two images? nospam <nospam@nospam.invalid> - 2014-01-23 16:32 -0500
        Re: Any quick, easy way to compare two images? Don Bruder <dakidd@sonic.net> - 2014-01-23 16:22 -0800
          Re: Any quick, easy way to compare two images? Alan Browne <alan.browne@FreelunchVideotron.ca> - 2014-01-23 19:48 -0500
            Re: Any quick, easy way to compare two images? Don Bruder <dakidd@sonic.net> - 2014-01-23 23:54 -0800
              Re: Any quick, easy way to compare two images? Doug Anderson <ethelthelogremovethis@gmail.com> - 2014-01-24 08:09 -0800
                Re: Any quick, easy way to compare two images? Don Bruder <dakidd@sonic.net> - 2014-01-24 08:44 -0800
          Re: Any quick, easy way to compare two images? nospam <nospam@nospam.invalid> - 2014-01-23 22:06 -0500
            Re: Any quick, easy way to compare two images? Don Bruder <dakidd@sonic.net> - 2014-01-23 23:37 -0800
  Re: Any quick, easy way to compare two images? Jolly Roger <jollyroger@pobox.com> - 2014-01-23 20:46 +0000
  Re: Any quick, easy way to compare two images? Lewis <g.kreme@gmail.com.dontsendmecopies> - 2014-01-23 23:19 +0000
    Re: Any quick, easy way to compare two images? Alan Browne <alan.browne@FreelunchVideotron.ca> - 2014-01-23 18:38 -0500
      Re: Any quick, easy way to compare two images? Lewis <g.kreme@gmail.com.dontsendmecopies> - 2014-01-24 00:49 +0000
        Re: Any quick, easy way to compare two images? Alan Browne <alan.browne@FreelunchVideotron.ca> - 2014-01-23 19:59 -0500
  Re: Any quick, easy way to compare two images? Doug Anderson <ethelthelogremovethis@gmail.com> - 2014-01-23 15:25 -0800
    Re: Any quick, easy way to compare two images? Alan Browne <alan.browne@FreelunchVideotron.ca> - 2014-01-23 18:37 -0500
      Re: Any quick, easy way to compare two images? Doug Anderson <ethelthelogremovethis@gmail.com> - 2014-01-23 16:05 -0800
        Re: Any quick, easy way to compare two images? Alan Browne <alan.browne@FreelunchVideotron.ca> - 2014-01-23 19:47 -0500
          Re: Any quick, easy way to compare two images? Doug Anderson <ethelthelogremovethis@gmail.com> - 2014-01-23 17:10 -0800
            Re: Any quick, easy way to compare two images? Alan Browne <alan.browne@FreelunchVideotron.ca> - 2014-01-24 17:42 -0500
              Re: Any quick, easy way to compare two images? Doug Anderson <ethelthelogremovethis@gmail.com> - 2014-01-24 16:42 -0800
                Re: Any quick, easy way to compare two images? Don Bruder <dakidd@sonic.net> - 2014-01-24 20:08 -0800
                Re: Any quick, easy way to compare two images? Alan Browne <alan.browne@FreelunchVideotron.ca> - 2014-01-25 10:54 -0500
                Re: Any quick, easy way to compare two images? JF Mezei <jfmezei.spamnot@vaxination.ca> - 2014-01-25 15:31 -0500
                Re: Any quick, easy way to compare two images? Don Bruder <dakidd@sonic.net> - 2014-01-25 17:31 -0800
                Re: Any quick, easy way to compare two images? Michael Vilain <vilain@NOspamcop.net> - 2014-01-25 17:57 -0800
                Re: Any quick, easy way to compare two images? Jolly Roger <jollyroger@pobox.com> - 2014-01-26 03:09 +0000
                Re: Any quick, easy way to compare two images? JF Mezei <jfmezei.spamnot@vaxination.ca> - 2014-01-25 23:02 -0500
                Re: Any quick, easy way to compare two images? Jolly Roger <jollyroger@pobox.com> - 2014-01-26 05:04 +0000
                Re: Any quick, easy way to compare two images? Alan Browne <alan.browne@FreelunchVideotron.ca> - 2014-01-25 10:58 -0500
                Re: Any quick, easy way to compare two images? Doug Anderson <ethelthelogremovethis@gmail.com> - 2014-01-25 10:29 -0800
                Re: Any quick, easy way to compare two images? Alan Browne <alan.browne@FreelunchVideotron.ca> - 2014-01-25 13:39 -0500
                Re: Any quick, easy way to compare two images? nospam <nospam@nospam.invalid> - 2014-01-25 13:45 -0500
                Re: Any quick, easy way to compare two images? Doug Anderson <ethelthelogremovethis@gmail.com> - 2014-01-25 13:27 -0800
                Re: Any quick, easy way to compare two images? nospam <nospam@nospam.invalid> - 2014-01-25 16:30 -0500
                Re: Any quick, easy way to compare two images? Doug Anderson <ethelthelogremovethis@gmail.com> - 2014-01-25 13:33 -0800
                Re: Any quick, easy way to compare two images? nospam <nospam@nospam.invalid> - 2014-01-25 16:52 -0500
                Re: Any quick, easy way to compare two images? JF Mezei <jfmezei.spamnot@vaxination.ca> - 2014-01-25 17:31 -0500
                Re: Any quick, easy way to compare two images? Jolly Roger <jollyroger@pobox.com> - 2014-01-25 22:35 +0000
                Re: Any quick, easy way to compare two images? nospam <nospam@nospam.invalid> - 2014-01-25 17:49 -0500
                Re: Any quick, easy way to compare two images? Tom Stiller <clusterfux.upmon@gmail.com> - 2014-01-25 22:55 +0000
                Re: Any quick, easy way to compare two images? JF Mezei <jfmezei.spamnot@vaxination.ca> - 2014-01-25 18:33 -0500
                Re: Any quick, easy way to compare two images? nospam <nospam@nospam.invalid> - 2014-01-25 19:42 -0500
                Re: Any quick, easy way to compare two images? Don Bruder <dakidd@sonic.net> - 2014-01-25 17:38 -0800
                Re: Any quick, easy way to compare two images? JF Mezei <jfmezei.spamnot@vaxination.ca> - 2014-01-25 22:50 -0500
                Re: Any quick, easy way to compare two images? Jolly Roger <jollyroger@pobox.com> - 2014-01-26 02:49 +0000
                Re: Any quick, easy way to compare two images? Lewis <g.kreme@gmail.com.dontsendmecopies> - 2014-01-26 14:21 +0000
                Re: Any quick, easy way to compare two images? Jolly Roger <jollyroger@pobox.com> - 2014-01-26 15:17 +0000
                Re: Any quick, easy way to compare two images? nospam <nospam@nospam.invalid> - 2014-01-26 14:04 -0500
                Re: Any quick, easy way to compare two images? Jolly Roger <jollyroger@pobox.com> - 2014-01-26 00:17 +0000
                Re: Any quick, easy way to compare two images? nospam <nospam@nospam.invalid> - 2014-01-25 19:42 -0500
                Re: Any quick, easy way to compare two images? dorayme <do_ray_me@bigpond.com> - 2014-01-26 12:23 +1100
                Re: Any quick, easy way to compare two images? Jolly Roger <jollyroger@pobox.com> - 2014-01-26 02:54 +0000
                Re: Any quick, easy way to compare two images? Jolly Roger <jollyroger@pobox.com> - 2014-01-26 02:52 +0000
                Re: Any quick, easy way to compare two images? nospam <nospam@nospam.invalid> - 2014-01-25 22:10 -0500
                Re: Any quick, easy way to compare two images? Jolly Roger <jollyroger@pobox.com> - 2014-01-26 03:32 +0000
                Re: Any quick, easy way to compare two images? nospam <nospam@nospam.invalid> - 2014-01-25 22:55 -0500
                Re: Any quick, easy way to compare two images? Jolly Roger <jollyroger@pobox.com> - 2014-01-26 05:02 +0000
                Re: Any quick, easy way to compare two images? nospam <nospam@nospam.invalid> - 2014-01-26 14:04 -0500
                Re: Any quick, easy way to compare two images? Doug Anderson <ethelthelogremovethis@gmail.com> - 2014-01-25 18:03 -0800
                Re: Any quick, easy way to compare two images? nospam <nospam@nospam.invalid> - 2014-01-25 22:10 -0500
                Re: Any quick, easy way to compare two images? nospam <nospam@nospam.invalid> - 2014-01-25 17:49 -0500
                Re: Any quick, easy way to compare two images? Savageduck <savageduck1@{REMOVESPAM}me.com> - 2014-01-25 15:59 -0800
                Re: Any quick, easy way to compare two images? Jolly Roger <jollyroger@pobox.com> - 2014-01-26 00:24 +0000
                Re: Any quick, easy way to compare two images? nospam <nospam@nospam.invalid> - 2014-01-25 19:42 -0500
                Re: Any quick, easy way to compare two images? Savageduck <savageduck1@{REMOVESPAM}me.com> - 2014-01-25 17:30 -0800
                Re: Any quick, easy way to compare two images? Jolly Roger <jollyroger@pobox.com> - 2014-01-26 02:57 +0000
                Re: Any quick, easy way to compare two images? JF Mezei <jfmezei.spamnot@vaxination.ca> - 2014-01-25 22:46 -0500
                Re: Any quick, easy way to compare two images? Jolly Roger <jollyroger@pobox.com> - 2014-01-26 03:49 +0000
                Re: Any quick, easy way to compare two images? nospam <nospam@nospam.invalid> - 2014-01-25 22:55 -0500
                Re: Any quick, easy way to compare two images? dorayme <do_ray_me@bigpond.com> - 2014-01-26 12:08 +1100
                Re: Any quick, easy way to compare two images? Savageduck <savageduck1@{REMOVESPAM}me.com> - 2014-01-25 17:31 -0800
                Re: Any quick, easy way to compare two images? dorayme <do_ray_me@bigpond.com> - 2014-01-26 13:00 +1100
                Re: Any quick, easy way to compare two images? Don Bruder <dakidd@sonic.net> - 2014-01-25 20:13 -0800
                Re: Any quick, easy way to compare two images? dorayme <do_ray_me@bigpond.com> - 2014-01-26 16:15 +1100
                Re: Any quick, easy way to compare two images? Doug Anderson <ethelthelogremovethis@gmail.com> - 2014-01-25 18:07 -0800
                Re: Any quick, easy way to compare two images? Savageduck <savageduck1@{REMOVESPAM}me.com> - 2014-01-25 18:24 -0800
                Re: Any quick, easy way to compare two images? Jolly Roger <jollyroger@pobox.com> - 2014-01-26 02:58 +0000
                Re: Any quick, easy way to compare two images? nospam <nospam@nospam.invalid> - 2014-01-25 22:10 -0500
                Re: Any quick, easy way to compare two images? Don Bruder <dakidd@sonic.net> - 2014-01-25 17:36 -0800
                Re: Any quick, easy way to compare two images? Savageduck <savageduck1@{REMOVESPAM}me.com> - 2014-01-25 17:51 -0800
                Re: Any quick, easy way to compare two images? Don Bruder <dakidd@sonic.net> - 2014-01-26 00:39 -0800
                Re: Any quick, easy way to compare two images? Jolly Roger <jollyroger@pobox.com> - 2014-01-26 15:43 +0000
                Re: Any quick, easy way to compare two images? Doug Anderson <ethelthelogremovethis@gmail.com> - 2014-01-26 08:19 -0800
                Re: Any quick, easy way to compare two images? Jolly Roger <jollyroger@pobox.com> - 2014-01-26 16:31 +0000
                Re: Any quick, easy way to compare two images? Doug Anderson <ethelthelogremovethis@gmail.com> - 2014-01-26 09:54 -0800
                Re: Any quick, easy way to compare two images? Jolly Roger <jollyroger@pobox.com> - 2014-01-26 18:14 +0000
                Re: Any quick, easy way to compare two images? Doug Anderson <ethelthelogremovethis@gmail.com> - 2014-01-26 10:44 -0800
                Re: Any quick, easy way to compare two images? Jolly Roger <jollyroger@pobox.com> - 2014-01-26 19:10 +0000
                Re: Any quick, easy way to compare two images? dorayme <do_ray_me@bigpond.com> - 2014-01-27 11:14 +1100
                Re: Any quick, easy way to compare two images? Doug Anderson <ethelthelogremovethis@gmail.com> - 2014-01-26 16:22 -0800
                Re: Any quick, easy way to compare two images? dorayme <do_ray_me@bigpond.com> - 2014-01-27 11:44 +1100
                Re: Any quick, easy way to compare two images? nospam <nospam@nospam.invalid> - 2014-01-27 13:06 -0500
                Re: Any quick, easy way to compare two images? Lewis <g.kreme@gmail.com.dontsendmecopies> - 2014-01-27 12:48 +0000
                Re: Any quick, easy way to compare two images? Doug Anderson <ethelthelogremovethis@gmail.com> - 2014-01-27 05:49 -0800
                Re: Any quick, easy way to compare two images? Alan Browne <alan.browne@FreelunchVideotron.ca> - 2014-01-26 12:05 -0500
                Re: Any quick, easy way to compare two images? Jolly Roger <jollyroger@pobox.com> - 2014-01-26 17:08 +0000
                Re: Any quick, easy way to compare two images? Alan Browne <alan.browne@FreelunchVideotron.ca> - 2014-01-26 12:27 -0500
                Re: Any quick, easy way to compare two images? Jolly Roger <jollyroger@pobox.com> - 2014-01-26 17:37 +0000
                Re: Any quick, easy way to compare two images? JF Mezei <jfmezei.spamnot@vaxination.ca> - 2014-01-26 15:36 -0500
                Re: Any quick, easy way to compare two images? Jolly Roger <jollyroger@pobox.com> - 2014-01-26 21:46 +0000
                Re: Any quick, easy way to compare two images? nospam <nospam@nospam.invalid> - 2014-01-26 14:04 -0500
                Re: Any quick, easy way to compare two images? Doug Anderson <ethelthelogremovethis@gmail.com> - 2014-01-26 12:16 -0800
                Re: Any quick, easy way to compare two images? Jolly Roger <jollyroger@pobox.com> - 2014-01-26 21:47 +0000
                Re: Any quick, easy way to compare two images? Doug Anderson <ethelthelogremovethis@gmail.com> - 2014-01-26 16:21 -0800
                Re: Any quick, easy way to compare two images? Jolly Roger <jollyroger@pobox.com> - 2014-01-27 01:57 +0000
                Re: Any quick, easy way to compare two images? Don Bruder <dakidd@sonic.net> - 2014-01-26 10:32 -0800
                Re: Any quick, easy way to compare two images? Jolly Roger <jollyroger@pobox.com> - 2014-01-26 18:54 +0000
                Re: Any quick, easy way to compare two images? JF Mezei <jfmezei.spamnot@vaxination.ca> - 2014-01-26 15:40 -0500
                Re: Any quick, easy way to compare two images? Savageduck <savageduck1@{REMOVESPAM}me.com> - 2014-01-26 13:30 -0800
                Re: Any quick, easy way to compare two images? Don Bruder <dakidd@sonic.net> - 2014-01-26 15:06 -0800
                Re: Any quick, easy way to compare two images? JF Mezei <jfmezei.spamnot@vaxination.ca> - 2014-01-26 18:20 -0500
                Re: Any quick, easy way to compare two images? Jolly Roger <jollyroger@pobox.com> - 2014-01-26 23:35 +0000
                Re: Any quick, easy way to compare two images? nospam <nospam@nospam.invalid> - 2014-01-27 13:06 -0500
                Re: Any quick, easy way to compare two images? Jolly Roger <jollyroger@pobox.com> - 2014-01-27 19:14 +0000
                Re: Any quick, easy way to compare two images? JF Mezei <jfmezei.spamnot@vaxination.ca> - 2014-01-27 23:18 -0500
                Re: Any quick, easy way to compare two images? Jolly Roger <jollyroger@pobox.com> - 2014-01-28 04:27 +0000
                Re: Any quick, easy way to compare two images? nospam <nospam@nospam.invalid> - 2014-01-29 14:01 -0500
                Re: Any quick, easy way to compare two images? nospam <nospam@nospam.invalid> - 2014-01-29 14:01 -0500
                Re: Any quick, easy way to compare two images? john hevelin <bwotte@panix.com> - 2014-01-27 01:19 +0000
                Re: Any quick, easy way to compare two images? Don Bruder <dakidd@sonic.net> - 2014-01-26 18:28 -0800
                Re: Any quick, easy way to compare two images? john hevelin <bwotte@panix.com> - 2014-01-28 02:26 +0000
                Re: Any quick, easy way to compare two images? Don Bruder <dakidd@sonic.net> - 2014-01-28 06:35 -0800
                Re: Any quick, easy way to compare two images? dorayme <do_ray_me@bigpond.com> - 2014-01-27 10:55 +1100
                Re: Any quick, easy way to compare two images? nospam <nospam@nospam.invalid> - 2014-01-25 22:10 -0500
                Re: Any quick, easy way to compare two images? Doug Anderson <ethelthelogremovethis@gmail.com> - 2014-01-25 21:41 -0800
                Re: Any quick, easy way to compare two images? nospam <nospam@nospam.invalid> - 2014-01-26 14:04 -0500
                Re: Any quick, easy way to compare two images? Jolly Roger <jollyroger@pobox.com> - 2014-01-26 03:13 +0000
                Re: Any quick, easy way to compare two images? JF Mezei <jfmezei.spamnot@vaxination.ca> - 2014-01-25 17:30 -0500
                Re: Any quick, easy way to compare two images? john hevelin <bwotte@panix.com> - 2014-01-25 18:51 +0000
                Re: Any quick, easy way to compare two images? Lewis <g.kreme@gmail.com.dontsendmecopies> - 2014-01-25 19:06 +0000
                Re: Any quick, easy way to compare two images? JF Mezei <jfmezei.spamnot@vaxination.ca> - 2014-01-25 15:37 -0500
                Re: Any quick, easy way to compare two images? JF Mezei <jfmezei.spamnot@vaxination.ca> - 2014-01-25 15:35 -0500
        Re: Any quick, easy way to compare two images? nospam <nospam@nospam.invalid> - 2014-01-23 22:06 -0500

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