c++


Mat copyTo from row to col doesn't work! Why?

霸气de小男生 提交于 2020-01-23 02:18:07
问题 This answer states how to copy a row of a matrix to another row: How to copy a row of a Mat to another Mat's column in OpenCv? However if I try to copy a row of a matrix to a column vector the program is ends abruptly. Example: Mat A(640,480,CV_64F); Mat B(480,1,CV_64F); A.row(0).copyTo(B.col(0)); A possible workaround is: Mat A(640,480,CV_64F); Mat B; A.row(0).copyTo(B); B = B.t(); But how can I get type CV_64F in B if A is a different type? Is the data type copied, too? And - most important

Qt signal and slots: are reference arguments copied?

余生长醉 提交于 2020-01-23 02:15:30
问题 In qt framework, most library signals and slots use pointers as parameters. I was wondering, If I create a signal-slot "structure" that takes a reference as the parameter instead of the pointer, will the whole parameter be copied, or just 4 bytes (32-bit system) like in a regular c++ reference? I am asking this because I noticed something when I create a signal/ slot methods with the reference parameter. When I then connect them, the autocomplete mechanism in QTCreator doesn't hint me with

can't initialize functor objects when passing derived class in C++

巧了我就是萌 提交于 2020-01-23 02:15:07
问题 This question stems from a previous question I asked here. I cannot use any external libraries or the C++ 11 spec. Meaning I can't use std::bind, std::function, boost::bind,boost::function etc. I have to write it myself. The issue is the following: Consider the code: EDIT Here is a complete program that exhibits the problem as requested: #include <map> #include <iostream> class Command { public: virtual void executeCommand() = 0; }; class Functor { public: virtual Command * operator()()=0; };

read txt file in c++ (chinese)

╄→гoц情女王★ 提交于 2020-01-23 02:12:28
问题 I'm trying to develop function that check whether chinese word which user enters is in the txt file or not. The following is the code. But it is not working. I want to know what the problem is. Help me please. setlocale(LC_ALL, "Chinese-simplified"); locale::global(locale("Chinese_China")); SetConsoleOutputCP(936); SetConsoleCP(936); bool exist = FALSE; cout << "\n\n <Find the keyword whether it is in that image or not> \n "; cout << "Enter word to search for: "; wstring search; wcin >>

JDK9 Hotspot debug using gdb, causing SIGSEGV Segmentation fault in eclipse/Ubuntu terminal

社会主义新天地 提交于 2020-01-23 02:11:52
问题 I am trying to debug JDK9. I want to trace source code and see the control flow of JDK/Hotspot code. I use gdb and Eclipse but there is a problem SIGSEGV Segmentation fault . I follow Buildme.md from JDK official document to configure JDK9, bash ./configure --with-debug-level=slowdebug --with-target-bits=64 --disable-warnings-as-errors Then, make all I get my customized debug version: /images/jdk/bin/java -version openjdk version "9-internal" OpenJDK Runtime Environment (build 9-internal+0

What happens when you run out of ram with mlockall set?

一世执手 提交于 2020-01-23 02:01:28
问题 I am working on a C++ application that requires a large amounts of memory for a batch run. (> 20gb) Some of my customers are running into memory limits where sometimes the OS starts swapping and the total run time doubles or worse. I have read that I can use the mlockall to keep the process from being swapped out. What would happen when the process memory requirements approaches or exceeds the the available physical memory in this way? I guess the answer might be OS specific so please list

How do I write binary data for 7z archive format?

拟墨画扇 提交于 2020-01-23 01:50:08
问题 I've been pouring over the format description and source code for the 7z archive format, but I'm still having trouble writing a valid container. I assume I can create an empty container... anyway here's my start: std::ofstream ofs(archivename.c_str(), std::ios::binary|std::ios::trunc); Byte signature[6] = {'7', 'z', 0xBC, 0xAF, 0x27, 0x1C}; Byte major = 0; Byte minor = 3; ofs.write((const char*)signature, 6); ofs.write((const char*)major, 1); ofs.write((const char*)minor, 1); UInt64 offset =

C++ function name demangling: What does this name suffix mean?

北慕城南 提交于 2020-01-23 01:39:31
问题 When I disassemble the Chromium binary I notice there are functions named in this pattern: _ZN6webrtc15DecoderDatabase11DecoderInfoD2Ev.part.1 If I give this string to c++filt, the output is webrtc::DecoderDatabase::DecoderInfo::~DecoderInfo() [clone .part.1] So what does this .part.1 suffix really mean? If it indicates there are multiple copies of the same function, why do they need that? Is it due to the requirement of being position independent? I used g++ as the compiler. 回答1: It

OpenCV - Fastest method to check if two images are 100% same or not

怎甘沉沦 提交于 2020-01-23 01:35:10
问题 There are many questions over here which checks if two images are "nearly" similar or not. My task is simple. With OpenCV, I want to find out if two images are 100% identical or not. They will be of same size but can be saved with different filenames. 回答1: You can use a logical operator like xor operator. If you are using python you can use the following one-line function: Python def is_similar(image1, image2): return image1.shape == image2.shape and not(np.bitwise_xor(image1,image2).any())

Polymorphism (inheritance) and value types

不问归期 提交于 2020-01-23 01:35:06
问题 I have a bunch of types, PixelMeasure , PointMeasure , CentimeterMeasure and so on, that represent a value with a unit. I would like them to have value semantics: e.g. effectively immutable, don't have to worry about memory allocation, and polymorphism: I can return an object of type Measure and can operate on it without knowning what specific kind it is. I would also like to be able to put multiple different Measure s into a container. It seems these are mutually exclusive in C++. For

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