I am using OpenCV 2.3.1 with Windows 8. When I call function cvShowImage the program crashes. I am using codeblocks and I don't know why this happens.
If I comment the line the program runs well.
The code looks as follows:
IplImage *img1=NULL;
img1=cvLoadImage("LenaComFormas.pgm",CV_LOAD_IMAGE_GRAYSCALE);
cvShowImage("Original", img1);
cvWaitKey(0);
your code is working fine with Qt and opencv 2.4.3 on Windows7...possible checks you can do...
check links to the libraries...opencv_core231 , opencv_highgui231 , opencv_imgproc231...check includes to opencv2/opencv/core.hpp opencv2/opencv/highgui.hpp.
check the IplImage pointer img1
IplImage *img1 = cvLoadImage("",0);
if(img1==NULL)
return -1;
3 . check the support of *.pgm images...or else get the latest opencv and try...
EDIT..
4 . just for check try the following..
#include <opencv/opencv2/core.hpp>
#include <opencv/opencv2/highgui.hpp>
using namespace cv;
int main()
{
Mat image;
image = imread("",0);
imshow("TEST",image);
waitKey(0);
return 0;
}
Because image wasn't load (cvLoadImage returned NULL). You can use debugger to check it. Check the path to the file again.
Related
I want to rasterize a shapefile in C or C++ using GDAL.
But the GDAL documentation is not explicit enough for me.
Does someone have a code sample, useful links or advice on how to do it properly?
Thanks.
This is the code I'm try to use but get error GDALRasterize(filename1,NULL,lineDS_shp, NULL,NULL)
GDALAllRegister();
char filename1[]="./datas/myRaster.tiff";
char filename3[]="./datas/janze_montlouis_transparent_mosaic_group1.tif";
char filename2[]="./datas/ExportPolylignes_lines.shp";
GDALDatasetH lineDS,lineDS_shp;
lineDS_shp = GDALOpenEx(filename2, GDAL_OF_VECTOR, NULL, NULL, NULL
);
lineDS = GDALRasterize(filename1,NULL,lineDS_shp,NULL,NULL);
GDALClose(lineDS_shp);
GDALClose(lineDS);
ERROR 1: Size and resolutions are missing
Process finished with exit code 0
As a first step on a larger project I was trying to display the imagem from my webcam using OpenCV:
#include <stdlib.h>
#include <opencv2/core/core.hpp>
#include <opencv2/highgui/highgui.hpp>
int
main()
{
cv::VideoCapture cap(-1);
if (!cap.isOpened())
exit(EXIT_FAILURE);
cv::Mat frame;
bool done = false;
while (!done) {
cap >> frame;
cv::imshow("webcam", frame);
done = (cv::waitKey(30) >= 0);
}
return EXIT_SUCCESS;
}
This returns an error code (!cap.isOpened() passes ,confirmed with gdb). Initially I had 0 instead of -1. When searching this site -1 was suggested, but it was to no avail. I also tried 1 through 3, as another user suggested it.
I can display my webcam using mplayer, more specifically mplayer tv:// -tv driver=v4l2.
v4l2 is the "video for linux" driver. I noticed OpenCV can be installed with such driver by compiling it with -DWITH_V4L and -DWITH_LIBV4L (v4l USE flag in Gentoo). After recompiling OpenCV with it, it successfully recognized the webcam. GTK support seems to be needed to display the image.
I have a code in C language that uses the cvopen Library.
Here is the code:
#include <stdio.h>
#include <opencv2\highgui\highgui_c.h>
int main(void)
{
int i;
cvNamedWindow("Display window", CV_WINDOW_AUTOSIZE); //create a window
//create an image
IplImage* image = cvLoadImage("C:\\Users\\magshimim\\Desktop\\Mummy.png", 1);
if (!image)//The image is empty.
{
printf("could not open image\n");
}
else
{
cvShowImage("Display window", image);
cvWaitKey(0);
system("pause");
cvReleaseImage(&image);
}
getchar();
return 0;
}
In line 17 "cvShowImage("Display window", image);" the system throws exception that says:
Exception thrown at 0xAD76406A in Q4.exe: 0xC0000008: An invalid handle was specified
The cvopen pack is fine, and other function works. but this code (which works on other computers) just crushes every time.
How can i fix this?
cvShowImage is part of the old C-style naming convention in OpenCV. This old convention has been fully depreciated and is not compatible with OpenCV 3.0 and up.
Instead of cvShowImage try using imshow
imshow("Display Window", image);
I'm new to OpenCV and I want to display what my webcam sees with OpenCV. I'm using the C Coding Language.
I've tried with this code:
#include <stdio.h>
#include <cv.h> // Include the OpenCV library
#include <highgui.h> // Include interfaces for video capturing
int main()
{
cvNamedWindow("Window", CV_WINDOW_AUTOSIZE);
CvCapture* capture =cvCreateCameraCapture(-1);
if (!capture){
printf("Error. Cannot capture.");
}
else{
cvNamedWindow("Window", CV_WINDOW_AUTOSIZE);
while (1){
IplImage* frame = cvQueryFrame(capture);
if(!frame){
printf("Error. Cannot get the frame.");
break;
}
cvShowImage("Window",frame);
}
cvReleaseCapture(&capture);
cvDestroyWindow("Window");
}
return 0;
}
My webcam's light turns on, but the result is a completely grey window, with no image.
Can you help me?
You need to add
cvWaitKey(30);
to the end of while-loop.
cvWaitKey(x) / cv::waitKey(x) does two things:
It waits for x milliseconds for a key press. If a key was pressed during that time, it returns the key's ASCII code. Otherwise, it returns -1.
It handles any windowing events, such as creating windows with cvNamedWindow(), or showing images with cvShowImage().
A common mistake for opencv newcomers is to call cvShowImage() in a loop through video frames, without following up each draw with cvWaitKey(30). In this case, nothing appears on screen, because highgui is never given time to process the draw requests from cvShowImage().
See What does OpenCV's cvWaitKey( ) function do? for more info.
I have some C code trying to use libharu. Although I can use every function of this library (even UTF8) I can hardly draw images. Here is some very basic code:
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <math.h>
#include <setjmp.h>
#include "hpdf.h"
jmp_buf env;
#ifdef HPDF_DLL
void __stdcall
#else
void
#endif
error_handler (HPDF_STATUS error_no,
HPDF_STATUS detail_no,
void *user_data)
{
printf ("ERROR: error_no=%04X, detail_no=%u\n", (HPDF_UINT)error_no,
(HPDF_UINT)detail_no);
longjmp(env, 1);
}
int main (int argc, char **argv)
{
HPDF_Doc pdf;
HPDF_Font font;
HPDF_Page page;
char fname[256];
HPDF_Image image;
strcpy (fname, argv[0]);
strcat (fname, ".pdf");
pdf = HPDF_New (error_handler, NULL);
if (!pdf) {
printf ("error: cannot create PdfDoc object\n");
return 1;
}
/* error-handler */
if (setjmp(env)) {
HPDF_Free (pdf);
return 1;
}
font = HPDF_GetFont (pdf, "Helvetica", NULL);
page = HPDF_AddPage (pdf);
HPDF_Page_SetWidth (page, 550);
HPDF_Page_SetHeight (page, 500);
image = HPDF_LoadPngImageFromFile (pdf, "img.png");
HPDF_SaveToFile (pdf, fname);
HPDF_Free (pdf);
return 0;
}
When I compile this I have ERROR: error_no=1015, detail_no=0. I have found a similar post in stackoverflow: this. However although original poster said the problem is solved it hardly helped mine. I moved img.png to a folder and recompiled the file. Changed the code that says /home/name/path/to/img.png which is the direct path to image. Nothing works. I "always" have the same error, but when I change the name of file I have ERROR: error_no=1017, detail_no=2 which basicly means program cannot find image (according to reference of libharu) So I deduce that program finds img.png; but, it's strange but, cannot allocate the necessary memory. Which is weird because I cannot see any reason for this program not to allocate memory. I have every kind of permission.
I am using GCC 4.7.2 under Ubuntu Quantal Quetzal and libharu 2.3.0 RC2. Thank you for your help.
Hello Equalities of polynomials .
I also encountered the same problem when i integrated the haru sdk in my macOS environment.
The error_handler returned ERROR: error_no=1017, detail_no=2,and then i checked the official document for haru at http://libharu.sourceforge.net/error_handling.html query 0x1017 indicates that the file failed to open, so i suspect that the second parameter of the HPDF_LoadPngImageFromFile method needs to pass an exact png image file path, so after I modified it, the problem was solved, and I hope to help you.
code ad follow:
char filename1[255];
strcpy(filename1, "/Users/xx/Downloads/lusaceg.com.png");
image = HPDF_LoadPngImageFromFile (pdf, filename1);
Faithfully yours.