November 2011 - Boost-users

[GIL] Array to image
by Sapp, Mark 08 Dec '11

08 Dec '11

Hi All, Can anyone point me in the right directions for copying or assigning an array in memory to an image? I'm reading an frame out of an AVI file using Microsoft's vfw32.lib/vfw.h and the function that grabs the frame returns a pointer to a bitmap in memory, like this: BYTE* pDIB = (BYTE*) AVIStreamGetFrame(pFrame, index); And I need to transfer that information into an image. I have extracted the bitmap header and have a pointer to the first pixel, so I suppose I could iterate over each pixel and channel and populate the image by hand, but I imagine there is a better way. Thanks, Mark Sapp Notice: This e-mail is intended solely for use of the individual or entity to which it is addressed and may contain information that is proprietary, privileged, company confidential and/or exempt from disclosure under applicable law. If the reader is not the intended recipient or agent responsible for delivering the message to the intended recipient, you are hereby notified that any dissemination, distribution or copying of this communication is strictly prohibited. If this communication has been transmitted from a U.S. location it may also contain data subject to the International Traffic in Arms Regulations or U.S. Export Administration Regulations and cannot be disseminated, distributed or copied to foreign nationals, residing in the U.S. or abroad, without the prior approval of the U.S. Department of State or appropriate export licensing authority. If you have received this communication in error, please notify the sender by reply e-mail or collect telephone call and delete or destroy all copies of this e-mail message, any physical copies made of this e-mail message and/or any file attachment(s).

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[filesystem] filesystem::absolute() doesn't work with ../relative_path or ./relative_path
by Sachin Garg 08 Dec '11

08 Dec '11

In boost 1.47.0 filesystem v3, boost::filesystem::absolute only appends the relative path to base path. It should also remove "./" from relative paths and "backtrack" on base path if relative path contains "../../" etc. For example, Input: "d:\current\path" ".\..\relative\path" Result obtained: "d:\current\path\.\..\relative\path" Desired result: "d:\current\relative\path" I have created a trac ticket for the same: https://svn.boost.org/trac/boost/ticket/5988 SG

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lexical_cast<uint_value_t<10>::least>("7") = 55
by Nathan Ridge 05 Dec '11

05 Dec '11

Whoops! uint_value_t<10>::least is unsigned char... Can something be done about this, like having uint_value_t<10>::least be something that looks and acts like an unsigned char but is recognized by lexical_cast to be an integer type, not a character type?

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Container with insertion order
by Claude 05 Dec '11

05 Dec '11

Is available in BOOST some container (set or map) that can keep the insertion order of elements? -- View this message in context: http://boost.2283326.n4.nabble.com/Container-with-insertion-order-tp4097717… Sent from the Boost - Users mailing list archive at Nabble.com.

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[python] converting C++ object to PyObject
by Johan Råde 05 Dec '11

05 Dec '11

I have three C++ classes X, Y and Z that I have exported from C++ to Python using python::class_. Now I want to write a factory function like PyObject* f(char c) { if(c == 'x') return new X; else if(c == 'y') return new Y; else if(c == 'z') return new Z; else PyErr_SetString(PyExc_ValueError, "Bad function argument"); } and export that function to Python. What is missing here is code that converts X*, Y* and Z* to PyObject*. How do I write that? Thank you, Johan

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BOOST_THROW_EXCEPTION causing Abort Trap
by Kieran Simpson 04 Dec '11

04 Dec '11

I'm trying to use `boost::exception` and have condensed my prototype code down to the example in the Boost exception tutorial (http://www.boost.org/doc/libs/1_47_0/libs/exception/doc/tutorial_transporti…) however when running the code with the `BOOST_THROW_EXCEPTION` macro I get an abort from the program. #include <iostream> #include <boost/exception/all.hpp> typedef boost::error_info<struct tag_my_info,int> my_info; struct my_error: virtual boost::exception, virtual std::exception { }; void f() { BOOST_THROW_EXCEPTION(my_error() << my_info(42)); // Uncomment the below (and comment the above) for the program to work //throw my_error() << my_info(42); } int main(int argc, char** argv) { try { f(); } catch(my_error& x) { if(int const* mi = boost::get_error_info<my_info>(x)) { std::cout << "My info: " << *mi << std::endl; } } return 0; } Running the code with the BOOST_THROW_EXCEPTION macro: $ ./a.out Abort trap If as the comment says, I swap the code, all is well $ ./a.out My info: 42 Below is the output from the g++ preprocessor for f() void f() { ::boost::exception_detail::throw_exception_(my_error() << my_info(42),__PRETTY_FUNCTION__,"main.cpp",14); } Software versions are: $ g++ -v Using built-in specs. Target: x86_64-apple-darwin10 Thread model: posix gcc version 4.4.6 (GCC) $ port list boost boost @1.47.0 devel/boost I'm on OSX SL using the tools provided by MacPorts. I've double checked the g++ search paths and there's only one copy of the boost hpp files and that's the ones that belong to the aforementioned boost package. I have no idea why the abort trap is being called. I admit I'm newish to C++. I've also asked this question on StackOverflow (http://stackoverflow.com/questions/8256874/boost-throw-exception-causing-ab…) Cheers,

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Changelog for 1.47.0 does not properly warn about critical bug
by Paul Harris 02 Dec '11

02 Dec '11

Hello, I discovered this bug by accident https://svn.boost.org/trac/boost/changeset/68866 which was only linked via the ticket mentioned below, The code below demonstrates that ANY wide-character string of the same length resolves to the same UUID ! Thats pretty darn serious, I expected to see a much more serious mention in the Changelog in boost 1.47.0... for UUID, there was only a mention of a few tickets including this one: https://svn.boost.org/trac/boost/ticket/5145 which only mentioned a WARNING in the description ! "Fixed warning: use of logical && with constant operand; switch to bitwise & or remove constant [-Wconstant-logical-operand]" Surely it should say something like "UUIDs for wide character strings are totally wrong" Note also that the Changelog link for UUID goes to Utility, not UUID. The code: #include <boost/uuid/name_generator.hpp> #include <boost/uuid/nil_generator.hpp> #include <boost/uuid/uuid_io.hpp> #include <iostream> using namespace boost::uuids; using namespace std; int main() { { cout << "WIDE" << endl; const wchar_t* a = L"one long string that is something like this and that blahh"; const wchar_t* b = L"hello there you long long string that looks nothing like t"; nil_generator nil; name_generator na(nil()); name_generator nb(nil()); uuid ua = na(a); uuid ub = nb(b); cout << to_string(ua) << endl; cout << to_string(ub) << endl; } { cout << "NARROW" << endl; const char* a = "one long string that is something like this and that blahh"; const char* b = "hello there you long long string that looks nothing like t"; nil_generator nil; name_generator na(nil()); name_generator nb(nil()); uuid ua = na(a); uuid ub = nb(b); cout << to_string(ua) << endl; cout << to_string(ub) << endl; } return 0; } the result: $ g++ main.cpp && ./a.out WIDE 4ffa48af-9685-5089-97ac-fe6627ead94c 4ffa48af-9685-5089-97ac-fe6627ead94c NARROW 73030b72-a864-5c7b-9963-c0bedff1283e da8943a6-26c9-5641-bd37-427b1b70d619 $ The two different wchar_t strings resolve to the same uuid !!! What am I doing wrong? thanks Paul

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Problem with user defined Boost Units system
by Stephen Torri 01 Dec '11

01 Dec '11

I am using Boost 1.45 and trying to use Boost Units to map the types of astrodynamic equation variables. I am getting an error with the following equation. The error is saying that the lvalue type for k2_divded_by_semi_major is wrong. The questions I have are: Q1: Did I defined my system correctly? (System file is attached - types.hpp) Q2: How do I define ratio in the system? For example I have some constants that define a conversion (1 earth radii = 6378 km). Q3: How do I define a variable type if its a fraction (e.g. radii / radian )? ---- EQUATION ---- sgp4::types::radii_t k2_divided_by_semi_major = m_k2 / pow<2> ( semi_major ); The types of variables are: m_k2 sgp4::types::radii_t semi_major sgp4::types::radian_t ---- ERROR ---- 1> [ 1> Unit=boost::units::unit<boost::units::list<boost::units::dim<boost::units::length_base_dimension,boost::units::static_rational<-1>>,boost::units::detail::merge_dimensions_impl<0,0>::apply<boost::units::dimensionless_type,boost::units::dimensionless_type>::type>,boost::units::homogeneous_system<boost::units::list<sgp4::types::radii_base_unit,boost::units::list<sgp4::types::radian_base_unit,boost::units::dimensionless_type>>>>, 1> Y=double 1> ] 1> and 1> [ 1> Unit=sgp4::types::sgp4_length_t, 1> Y=double 1> ] 1> Constructor for class 'boost::units::quantity<Unit,Y>' is declared 'explicit' 1> with 1> [ 1> Unit=sgp4::types::sgp4_length_t, 1> Y=double 1> ] Regards, Stephen

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[Units] Temperature conversion problem
by Belcourt, Kenneth 01 Dec '11

01 Dec '11

Hi, There appears to be a temperature conversion problem between ºC and ºF. Here's a simple test that shows the error under both gcc and Intel on both Darwin and Linux (with Boost trunk). brisc:~ kbelco$ cat test3.cpp #include <iostream> #include <boost/units/io.hpp> #include <boost/units/quantity.hpp> #include <boost/units/systems/temperature/celsius.hpp> #include <boost/units/systems/temperature/fahrenheit.hpp> int main(int, char **) { using namespace boost::units; quantity<fahrenheit::temperature> t(100 * celsius::temperature()); // expect output of 212 F, produces 180 F // seems like not adding 32º offset when computing F = (C * 9/5 + 32) std::cout << t << std::endl; return 0; } brisc:~ kbelco$ icpc -g -Iboost test3.cpp brisc:~ kbelco$ ./a.out 180 F -- Noel

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fusion newby question - boost stew
by Robert Ramey 01 Dec '11

01 Dec '11

I'm experimenting with fusion and I have a question regarding the compatibiliy/interaction with MPL. in .. /libs/fusion/doc/html/fusion/introduction.html it states: "Fusion provides full round compatibility with MPL. Fusion sequences are fully conforming MPL sequences and MPL sequences are fully compatible with Fusion. You can work with Fusion sequences on MPL if you wish to work solely on types [1]. In MPL, Fusion sequences follow MPL's sequence-type preserving semantics" So when I compare the pages for the concept of AssociativeSequence for fusion: libs/fusion/doc/html/fusion/sequence/concepts/associative_sequence.html and that for MPL libs/mpl/doc/refmanual/associative-sequence.html the expression requirements are not the same. The metafunctions for fusion are: result_of::has_key<S, K>::type result_of::at_key<S, K>::type result_of::value_at_key<S, K>::type while for MPL they are has_key<s,k>::type count<s,k>::type order<s,k>::type at<s,k>::type at<s,k,def>::type key_type<s,x>::type value_type<s,x>::type So how can the statement in the fusion introduction be true? This question comes about as I'm making a new "thing" of my own invention where I want to inter-operate with purely type sequences created with MPL - just likt it says you can do in the documentation. Turns out at significant part of this "boost stew" depends on better compile time checking of the users's metafunction invocation. This ends up creating the need for concepts in both MPL which as far as I know haven't yet been coded. So when I do this, I run accross this question. I realize I can build a fusion sequence from an MPL one, but given the language in the introduction, I would have expected to be able to go both ways and this wouldn't seem to be true. Note that it's quite possible that I'm missing something here as I feel that I'm really starting to get this stuff only for the first time. Robert Ramey

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