I'm new to open cv. At the moment I'm trying to test if I could run a simple file.
// Example showing how to read and write images
#include <opencv2/opencv.hpp>
#include <opencv2/highgui/highgui.hpp>
#include <opencv/cvaux.h>
int main(int argc, char** argv)
{
IplImage * pInpImg = 0;
// Load an image from file - change this based on your image name
pInpImg = cvLoadImage("bear.jpg", CV_LOAD_IMAGE_UNCHANGED);
if(!pInpImg)
{
fprintf(stderr, "failed to load input image\n");
return -1;
}
// Write the image to a file with a different name,
// using a different image format -- .png instead of .jpg
if( !cvSaveImage("my_image_copy.png", pInpImg) )
{
fprintf(stderr, "failed to write image file\n");
}
// Remember to free image memory after using it!
cvReleaseImage(&pInpImg);
return 0;
}
I compiled it:
g++ `pkg-config –cflags opencv` cv.cpp -o cv `pkg-config –libs opencv`
I got this error:
Undefined symbols for architecture x86_64:
"_cvLoadImage", referenced from:
_main in cv-zQ5X30.o
"_cvReleaseImage", referenced from:
_main in cv-zQ5X30.o
"_cvSaveImage", referenced from:
_main in cv-zQ5X30.o
ld: symbol(s) not found for architecture x86_64
clang: error: linker command failed with exit code 1 (use -v to see invocation)
I'm lost here, any help would be very much appreciated.
Thank you.
i think the problem might be using "-libs" and "-cflags" instead of "--libs" and "--cflags", use this instead:
g++ `pkg-config --cflags opencv` cv.cpp -o cv `pkg-config --libs opencv`
Related
I am trying to run a program that opens a window. the purpose is to get the program started opening a window is the start of all programs right?
But when I run my code for some reason I get this error:
Undefined symbols for architecture x86_64:
"_main", referenced from:
implicit entry/start for main executable
ld: symbol(s) not found for architecture x86_64
clang: error: linker command failed with exit code 1 (use -v to see invocation)
However, in my code I do have the main() function so why am I getting this error?
This is my code:
#include <SDL2/SDL.h>
#include <SDL2_image/SDL_image.h>
#include <SDL2_ttf/SDL_ttf.h>
#include <stdio.h>
int main(){
if(SDL_Init( SDL_INIT_EVERYTHING ) < 0){
std::cout << "error 1\n";
std::cout << SDL_GetError();
std::cout << "\n";
return -1;
}
if(TTF_Init() < 0){
std::cout << "error 2\n";
std::cout << TTF_GetError();
std::cout << "\n";
return -1;
}
SDL_Window* window = SDL_CreateWindow("test", 0, 0, 500, 500, 0);
if(!window){
std::cout << "error 3\n";
std::cout << SDL_GetError();
std::cout << "\n";
return -1;
}
int windowid = SDL_GetWindowID(window);
SDL_Renderer* Renderer = SDL_CreateRenderer(window, -1, 0);
running = true;
SDL_Event event;
while(running){
while(SDL_PollEvent(&event)){
if(event.type == SDL_WindowEvent){
if(event.window.windowID == windowid){
if(event.window.type == SDL_WindowClose){
Destroywindow(window);
running = false;
}
}
}
}
}
return 0;
}
my make file looks like this:
#!/bin/bash
brew update
brew install sdl2
g++ -o /Users/mikahshattuck/noneproject/none2019-05-0909-22-
14:2:/none.app/Contents/MacOS/mainrun.cpp -I /Library/Frameworks -l
SDL2
exit 0
this is the full out:
Already up-to-date.
Warning: sdl2 2.0.9_1 is already installed and up-to-date
To reinstall 2.0.9_1, run `brew reinstall sdl2`
Undefined symbols for architecture x86_64:
"_main", referenced from:
implicit entry/start for main executable
ld: symbol(s) not found for architecture x86_64
clang: error: linker command failed with exit code 1 (use -v to see
invocation)
logout
Saving session...
...copying shared history...
...saving history...truncating history files...
...completed.
[Process completed]
thank you in advance
When using SDL on macOS or Windows, you need to add -Dmain=SDL_main to your compile flags and -lSDL2main to your link flags. Since you're using Homebrew, you can make it easier and just use pkg-config to get the correct flags. Use this compiler command as a template and adapt it to your needs:
g++ $(pkg-config --cflags sdl2) -I /Library/Frameworks source.cpp -o output_executable $(pkg-config --libs sdl2)
However, it seems you are also using SDL_ttf, not just plain SDL. In this case, you should probably use SDL2_ttf instead of sdl2 as the package argument of pkg-config:
g++ $(pkg-config --cflags SDL2_ttf) -I /Library/Frameworks source.cpp -o output_executable $(pkg-config --libs SDL2_ttf)
The SDL2_ttf package depends on the sdl2 package, so using SDL2_ttf will also emit the needed flags for sdl2.
The names of the pkg-config packages correspond to *.pc files installed by Homebrew into /usr/local/lib/pkgconfig.
I have installed OpenCV 3.3.0 to Ubuntu 16.04. Just want to compile this code.
#include <iostream>
using namespace std;
#include "opencv2/opencv.hpp"
#include "opencv2/gpu/gpu.hpp"
#include <opencv2/opencv.hpp>
#include <opencv2/imgproc/imgproc.hpp>
#include <cmath>
using namespace cv;
int main(int argc, char* argv[])
{
try
{
int kernel_size = 3;
cv::Mat src_host = cv::imread("crack2.jpg");
cv::Mat gray_img, avg, kernel;
cv::gpu::GpuMat dst, src;
src.upload(src_host);
cv::gpu::threshold(src, dst, 128.0, 255.0, CV_THRESH_BINARY);
cv::Mat result_host;
dst.download(result_host);
std::cout<< "Done!!!" <<std::endl;
}catch(const cv::Exception& ex)
{
std::cout<<"Error: " << ex.what() << std::endl;
}
return 0;
}
g++ -o main gpu_thresh.cpp 'pkg-config opencv --cflags --libs' -lopencv_gpu -lopencv_core
g++ -L/usr/local/lib -o main gpu_thresh.cpp 'pkg-config opencv --cflags --libs' -lopencv_gpu -lopencv_core
I tried to compile it with these ways but still giving same warning and error.
/usr/bin/ld: warning: libopencv_core.so.2.4, needed by
/usr/lib/gcc/x86_64-linux-gnu/5/../../../x86_64-linux-gnu/libopencv_gpu.so,
may conflict with libopencv_core.so.3.3 /usr/bin/ld: /tmp/ccdhLGL0.o:
undefined reference to symbol '_ZN2cv3gpu6GpuMat7releaseEv'
//usr/lib/x86_64-linux-gnu/libopencv_core.so.2.4: error adding
symbols: DSO missing from command line collect2: error: ld returned 1
exit status
What should I do?
There's no opencv2/gpu/gpu.hpp in OpenCV 3.3. If your code compiles then it means that you've both OpenCV 2.4 and 3.3 on your machine.
In OpenCV 3.3, include:
#include <opencv2/core/cuda.hpp>
and then use
cv::cuda::GpuMat img;
See details here.
Edit: I just noticed your compilation method. When using pkg-config opencv --cflags --libs, you don't need to manually add the libopencv files anymore.
Just do: g++ -o main gpu_thresh.cpp 'pkg-config opencv --cflags --libs'
I've been learning C++ and have decided to try to create a simple file reader using libzip on archive files (e.g. Word).
I’ve recently installed libzip on my Macbook using brew but I seem to keep on getting the following issue whenever I try to compile a program that uses libzip:
Undefined symbols for architecture x86_64:
"_zip_fopen", referenced from:
_main in main-918bfa.o
"_zip_open", referenced from:
_main in main-918bfa.o
ld: symbol(s) not found for architecture x86_64
clang: error: linker command failed with exit code 1 (use -v to see invocation)
make: *** [a.exe] Error 1
The command I use to compile:
g++ -g main.cpp -std=c++11 -I/usr/local/Cellar/libzip/0.11.2/include -I/usr/local/Cellar/libzip/0.11.2/lib/libzip/include -L/usr/local/Cellar/libzip/0.11.2/lib -o ../a.exe
main.cpp:
#include <iostream>
#include <fstream>
#include <zip.h>
#include <zlib.h>
using namespace std;
int numArgs = 2;
int main(int argc, char** argv){
// Parse command line arguments
if(argc != numArgs){
std::cout << "Incorrect number of arguments provided.\n";
std::cout << "Command line syntax: fileReader.exe inputFile" << endl;
exit(0);
}
// Try out libzip functionality
std::string inputDocument(argv[1]);
int err = 0;
zip* z = zip_open(inputDocument.c_str(), 0, &err);
if(z == NULL) {
printf("Could not read docx file. Error code: %d", err);
exit(-1);
}
zip_file* contentTypes = zip_fopen(z, "[Content_Types].xml", ZIP_FL_UNCHANGED);
exit(0);
}
Doesn't look like your including the libzip library in the compilation command. Try adding -lzip to your g++ command
I installed Ubuntu 14.04 and Opencv using the steps mentioned here https://solarianprogrammer.com/2014/04/21/opencv-beaglebone-black-ubuntu/
I am trying to compile the following code (saved in text file named as test2.cpp. test2.cpp and lena.jpg were copied to beaglebone home folder) :
// Test to convert a color image to gray
// Build on Linux with:
// g++ test2.cpp -o test2 -lopencv_core -lopencv_imgproc -lopencv_highgui
#include <opencv2/opencv.hpp>
#include <iostream>
int main() {
// Load the image file and check for success
cv::Mat input = cv::imread("lena.jpg", 1);
if(!input.data) {
std::cout << "Unable to open the image file" << std::endl;
return -1;
}
// Convert the input file to gray
cv::Mat gray_image;
cvtColor(input, gray_image, cv::COLOR_BGR2GRAY);
// Save the result
cv::imwrite("lena_gray.jpg", gray_image);
return 0;
}
using g++ test2.cpp -o test2 -lopencv_core -lopencv_imgproc -lopencv_highgui
I also tried telling the compiler where the libraries are using -L /usr/local/lib . (the libopencv files were found there). But got the following error each time:
ubuntu#arm:~$ g++ test2.cpp -o test2 -lopencv_core -lopencv_imgproc -lopencv_highgui -L usr/local/lib
/tmp/cckXjOPd.o: In function `main':
test2.cpp:(.text+0x26): undefined reference to `cv::imread(cv::String const&, int)'
test2.cpp:(.text+0xf0): undefined reference to `cv::imwrite(cv::String const&, cv::_InputArray const&, std::vector<int, std::allocator<int=""> > const&)'
collect2: error: ld returned 1 exit status
Can someone help me out here? Any help would be appreciated.
I find it always convenient and safe to compile using:
g++ test2.cpp -o test2 `pkg-config --libs --cflags opencv`
Install pkg-config if not already present.
I am working on getting a few files to link together using my make file and c++ and am getting the following error when running make.
g++ -bind_at_load `pkg-config --cflags opencv` -c -o compute_gist.o compute_gist.cpp
g++ -bind_at_load `pkg-config --cflags opencv` -c -o gist.o gist.cpp
g++ -bind_at_load `pkg-config --cflags opencv` -c -o standalone_image.o standalone_image.cpp
g++ -bind_at_load `pkg-config --cflags opencv` -c -o IplImageConverter.o IplImageConverter.cpp
g++ -bind_at_load `pkg-config --cflags opencv` -c -o GistCalculator.o GistCalculator.cpp
g++ -bind_at_load `pkg-config --cflags opencv` `pkg-config --libs opencv` compute_gist.o gist.o standalone_image.o IplImageConverter.o GistCalculator.o -o rungist
Undefined symbols for architecture x86_64:
"color_gist_scaletab(color_image_t*, int, int, int const*)", referenced from:
_main in compute_gist.o
ld: symbol(s) not found for architecture x86_64
collect2: ld returned 1 exit status
make: *** [rungist] Error 1
My makefile is as follows (Note, I don't need opencv bindings yet, but will be coding in opencv later.
CXX = g++
CXXFLAGS = -bind_at_load `pkg-config --cflags opencv`
LFLAGS = `pkg-config --libs opencv`
SRC = \
compute_gist.cpp \
gist.cpp \
standalone_image.cpp \
IplImageConverter.cpp \
GistCalculator.cpp
OBJS = $(SRC:.cpp=.o)
rungist: $(OBJS)
$(CXX) $(CXXFLAGS) $(LFLAGS) $(OBJS) -o $#
all: rungist
clean:
rm -rf $(OBJS) rungist
The method header is located in gist.h
float *color_gist_scaletab(color_image_t *src, int nblocks, int n_scale, const int *n_orientations);
And the method is defined in gist.cpp
float *color_gist_scaletab(color_image_t *src, int w, int n_scale, const int *n_orientation) {
And finally the compute_gist.cpp (main file)
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include "gist.h"
static color_image_t *load_ppm(const char *fname) {
FILE *f=fopen(fname,"r");
if(!f) {
perror("could not open infile");
exit(1);
}
int width,height,maxval;
if(fscanf(f,"P6 %d %d %d",&width,&height,&maxval)!=3 || maxval!=255) {
fprintf(stderr,"Error: input not a raw PPM with maxval 255\n");
exit(1);
}
fgetc(f); /* eat the newline */
color_image_t *im=color_image_new(width,height);
int i;
for(i=0;i<width*height;i++) {
im->c1[i]=fgetc(f);
im->c2[i]=fgetc(f);
im->c3[i]=fgetc(f);
}
fclose(f);
return im;
}
static void usage(void) {
fprintf(stderr,"compute_gist options... [infilename]\n"
"infile is a PPM raw file\n"
"options:\n"
"[-nblocks nb] use a grid of nb*nb cells (default 4)\n"
"[-orientationsPerScale o_1,..,o_n] use n scales and compute o_i orientations for scale i\n"
);
exit(1);
}
int main(int argc,char **args) {
const char *infilename="/dev/stdin";
int nblocks=4;
int n_scale=3;
int orientations_per_scale[50]={8,8,4};
while(*++args) {
const char *a=*args;
if(!strcmp(a,"-h")) usage();
else if(!strcmp(a,"-nblocks")) {
if(!sscanf(*++args,"%d",&nblocks)) {
fprintf(stderr,"could not parse %s argument",a);
usage();
}
} else if(!strcmp(a,"-orientationsPerScale")) {
char *c;
n_scale=0;
for(c=strtok(*++args,",");c;c=strtok(NULL,",")) {
if(!sscanf(c,"%d",&orientations_per_scale[n_scale++])) {
fprintf(stderr,"could not parse %s argument",a);
usage();
}
}
} else {
infilename=a;
}
}
color_image_t *im=load_ppm(infilename);
//Here's the method call -> :(
float *desc=color_gist_scaletab(im,nblocks,n_scale,orientations_per_scale);
int i;
int descsize=0;
//compute descriptor size
for(i=0;i<n_scale;i++)
descsize+=nblocks*nblocks*orientations_per_scale[i];
descsize*=3; // color
//print descriptor
for(i=0;i<descsize;i++)
printf("%.4f ",desc[i]);
printf("\n");
free(desc);
color_image_delete(im);
return 0;
}
Any help would be greatly appreciated. I hope this is enough info. Let me know if I need to add more.
I suspect that color_gist_scaletab should be declared as extern "C" in your header file:
extern "C" {
float *color_gist_scaletab(color_image_t *src, int nblocks, int n_scale, const int *n_orientations);
}
Your link command line is incorrect. See this answer.
However, that is likely not the problem you are seeing here.
What do the following commands print?
file gist.o
nm gist.o | grep color_gist_scaletab
I also see this very similar question. But there, color_gist_scaletab comes from gist.c, not gist.cpp. You didn't just rename gist.c to gist.cpp, did you? Don't do that.