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Subject: [Boost-announce] [Review][GIL] Boost.GIL IO and Toolbox extensions have been ACCEPTED into Boost
From: Mateusz Loskot (mateusz_at_[hidden])
Date: 2011-01-27 08:35:57

Dear All,

The formal review of IO and Toolbox extensions for Boost.GIL [1]
ended on December 17th, 2010 [2]
The review subject was not a standalone library but a part of whole
   - an extension to existing Boost.GIL.

The review result: ACCEPTED

Number of received discussion and feedback posts is ~140.
I consider most of them in-topic, significant and also insightful.
Reviewers pointed issues already known from previous discussions on the
mailing list as well as new topics regarding the design and
implementation of the extensions. Also, issues related to the library
itself (Boost.GIL) were addressed. Some of them could be considered
ideas for future works and improvements.

It is remarkable, most (if not all) of the discussions were focused
on the IO extension. None of the submitted reviews include
comments to the Toolbox extension.

Formally, the review concluded with 1 NO and 7 YES votes.

Some of the YES votes are considered as conditional and
number of changes were requested by the reviewers.
The following changes should be addressed before the extensions
appear in the Boost mainstream:

1. Documentation is adequate, but requires clean-up and fixing of
    lots of typos.

2. Additional tests are added to exercise currently untested error
    cases that result in a longjmp should be added. They should pass
    on all platforms officially supported by Boost.

3. Make sure the test images are license-free. If the license
    status is unknown, change them to other license-free images.

4. The requirements for adding new file formats / backends to be made
    more explicit. This means defining concept for a file format
    reader/writer, etc. and adding new file formats would constitute
    providing models for these concepts.

5. Support for reading images whose file format is unknown at compile
    time. That involves the ability to register file formats / backends,
    associate them with given extensions and then call the appropriate
    reader based on the extension of the file name.

6. Support for different backends for the same image formats.
    It appears that this can be done simply the same way a file format
    can be extended, i.e. have "png_libpng" and "png_lodepng" tags.

7. Support for efficient reading/writing of parts of images that are
    too large to fit in memory. There are two ways to proceed:
    one is to have an input/output iterator that enforces sequential
    access, and another is to allow for user-driven access at the cost
    of sometimes severe performance.

The reviewers also posted a few suggestions that could improve
quality of the two extensions,

1. Name of functions like read_int8, read_int16, read_int32, write_int8
    in Device models suggest they return and accept signed integers,
    but they return and accept unsigned integers. The naming could
    be improved..

2. Do some profiling and performance optimization of the most common
    formats. Add some test cases to measure speed of common scenarios.

3. Make sure the test cases provide complete coverage. For example,
    set a breakpoint in every method, every switch statement and branch.
    Run your tests and remove any breakpoints that are encountered.
    Look at the breakpoints that were not hit and add tests for them.

4. It would be great if Christian and Domagoj could join their
    efforts to take the best of their libraries (IO extension
    implementations) to the IO extension included in Boost.GIL
    and collaborate for the advanced features discussed in reviews.

I would like to thank Edd Dawson, Zach Laine, Domagoj Saric, Roland
Bock, Lubomir Bourdev, Tom Brinkman, Phil Endecott, Kenny Riddile for
reviews and others who participated in discussions.
Thanks also go to Christian Henning for great work.

I would like conclude recalling short comment Lubomir Bourdev
included in his review. In my opinion, it is a good summary of the
Boost.GIL IO and Toolbox review and generally all discussions
on this subject:

The problem with I/O is that you can never declare success.
All we can hope for is push the boundary as much as we can,
and leave the rest for the next update.


Best regards,

Mateusz Loskot,
Charter Member of OSGeo,
Member of ACCU,

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