In opencv 2.4.6. I am trying to load a mat image file with a simple code given below. But the image is not loaded as I print the image size, it is showing '0'. Can anybody please tell me , what is going wrong?
int main(int argc, char argv[])
{
Mat a=imread("C:/image3.jpg");
cv::Size frame11_size = a.size();
printf("%d",frame11_size.height);
return 0;
}
Update: I solved the problem. The problem was, I was only including all the library,include and additional dependencies in 'debug mode' only. I did not change anything in 'release mode'. When I change the properties in 'release mode' as-well, it worked. thanks all for your kind responses, I am giving '+1' for your answers.
I think there should be single slash on your image path, and always check whether image is successfully loaded.
Mat a=imread("C:/image3.jpg");
if(! a.data ) // Check for invalid input
{
cout << "Could not open or find the image" << std::endl ;
return -1;
}
OpenCV can't open jpg files by itself. It depends on third parties to do so. Maybe you are missing certain dlls, or maybe your OpenCV installation don't have the right path to them. To test this assumption store your image in other formats. For example pgm or ppm. Those formats does not perform any encoding and just store image buffer in file as is. As a result OpenCV will not need any external libraries to open image in ppm format.
Related
my goal is to capture a frame from a rtmp stream every second, and process it using OpenCV. I'm using FFmpeg version N-71899-g6ef3426 and OpenCV 2.4.9 with the Java interface (but I'm first experimenting with Python).
For the moment, I can only take the simple and dirty solution, which is to capture images using FFmpeg, store them in disk, and then read those images from my OpenCV program. This is the FFmpeg command I'm using:
ffmpeg -i "rtmp://antena3fms35livefs.fplive.net:1935/antena3fms35live-live/stream-lasexta_1 live=1" -r 1 capImage%03d.jpg
This is currently working for me, at least with this concrete rtmp source. Then I would need to read those images from my OpenCV program in a proper way. I have not actually implemented this part, because I'm trying to find a better solution.
I think the ideal way would be to capture the rtmp frames directly from OpenCV, but I cannot find the way to do it. This is the code in Python I'm using:
cv2.namedWindow("camCapture", cv2.CV_WINDOW_AUTOSIZE)
cap = cv2.VideoCapture()
cap.open('"rtmp://antena3fms35livefs.fplive.net:1935/antena3fms35live-live/stream-lasexta_1 live=1"')
if not cap.open:
print "Not open"
while (True):
err,img = cap.read()
if img and img.shape != (0,0):
cv2.imwrite("img1", img)
cv2.imshow("camCapture", img)
if err:
print err
break
cv2.waitKey(30)
Instead of read() function, I'm also trying with grab() and retrieve() functions without any good result. The read() function is being executed every time, but no "img" or "err" is received.
Is there any other way to do it? or maybe there is no way to get frames directly from OpenCV 2.4.9 from a stream like this?
I've read OpenCV uses FFmpeg to do this kind of tasks, but as you can see, in my case FFmpeg is able to get frames from the stream while OpenCV is not.
In the case I could not find the way to get the frames directly from OpenCV, my next idea is to pipe somehow, FFmpeg output to OpenCV, which seems harder to implement.
Any idea,
thank you!
UPDATE 1:
I'm in Windows 8.1. Since I was running the python script from Eclipse PyDev, this time I run it from cmd instead, and I'm getting the following warning:
warning: Error opening file (../../modules/highgui/src/cap_ffmpeg_impl.hpp:545)
This warning means, as far as I could read, that either the file-path is wrong, or either the codec is not supported. Now, the question is the same. Is OpenCV not capable of getting the frames from this source?
Actually I have spent more that one day to figure out how to solve this issue. Finally I have solved this problem with the help of this link.
Here is client side code.
#include <opencv2/core/core.hpp>
#include <opencv2/imgproc/imgproc.hpp>
#include <opencv2/highgui/highgui.hpp>
#include <opencv2/opencv.hpp>
using namespace cv;
int main(int, char**) {
cv::VideoCapture vcap;
cv::Mat image;
const std::string videoStreamAddress = "rtmp://192.168.173.1:1935/live/test.flv";
if(!vcap.open(videoStreamAddress)) {
std::cout << "Error opening video stream or file" << std::endl;
return -1;
}
cv::namedWindow("Output Window");
cv::Mat edges;
for(;;) {
if(!vcap.read(image)) {
std::cout << "No frame" << std::endl;
cv::waitKey();
}
cv::imshow("Output Window", image);
if(cv::waitKey(1) >= 0) break;
}
}
Note: In this case I have created a android application to get real time video and send it to rtmp server wowza which is deployed in PC.So that is where I created this c++ implementation for real time video processing.
python -c "import cv2; print(cv2.getBuildInformation())"
check build opencv with ffmpeg。If it is correct, your code should be fine。
If not, rebuild opencv with ffmpeg。
Under osx
brew install opencv --with-ffmpeg
I was using OpenCV to read the images from a folder. A lot of messages like this show up:
Corrupt JPEG data: premature end of data segment
Premature end of JPEG file
Premature end of JPEG file
Premature end of JPEG file
How to catch this exception and remove these image files?
Since you said you are reading 'images' (multiple images), you would be looping through files in the folder that you are reading them from.
In that case, if you check if the image is valid or not by using the following :
Mat image;
image = imread(argv[1], CV_LOAD_IMAGE_COLOR); // Read the file
if(! image.data ) // Check for invalid input
{
cout << "Could not open or find the image" << std::endl ;
return -1;
}
you can then proceed to deleting files which are corrupt/bad.
I've been struggling to find a solution too. Read tens of articles, most of which just state that openCV does not throw errors and only outputs the error on stderr.
Some suggest to use PIL, but that does not detect most of the image corruptions. Usually only premature end of file.
However the same errors that OpenCV warns about can be detected via imagemagick.
Install imagemagick (https://imagemagick.org/)
Make sure you have it in the path.
Put the following sub into your code and call it to verify a file from wherever you need to. It also outputs errors to stderr, however it raises an error (thanks to "-regard-warnings")
import subprocess
def checkFile(imageFile):
try:
subprocess.run(["identify", "-regard-warnings", imageFile]).check_returncode()
return true
except (subprocess.CalledProcessError) as e:
return false
If you don't want the check to spam your outputs, add stdout=subprocess.DEVNULL, stderr=subprocess.DEVNULL params to the run function call.
On windows if you have not installed the legacy commands use the new syntax:
subprocess.run(["magick", "identify", "-regard-warnings", imageFile]).check_returncode()
I'm using cmake to build my project with opencv. There are two sub-projects, A and B, under the top directory. A has no opencv function while B uses VideoCapture to get image from webcam. There is no problem at first.
However, after I add the code from B to A, B can still capture image from webcam, but A cannot do the same thing, the error is below:
HIGHGUI ERROR: V4L2: Pixel format of incoming image is unsupported by OpenCV
VIDIOC_STREAMON: Inappropriate ioctl for device
It is strange, and I find that VideoCapture cannot get image in A, the code is below
VideoCapture cam;
cam.open(0);
if(!cam.isOpened()){
cout << "Failed to open webcam" << endl;
return false;
}
Mat Image;
cam >> Image;
if(Image.empty())
cout<<"Image empty"<<endl;
"Image empty" is always in console, which means it just cannot capture the image at all!!
I followed some suggestions such as install "v4l2ucp", but there is no folder under "/usr/lib/" named "libv4l", so LD_PRELOAD=/usr/lib/libv4l/v4l1compat.so dose not work.
I will very appreciate it if someone could give me some help to solve the problem in project A.
The file might not necessarily be there. Try find / -name "*v4l1compat.so*" 2>/dev/null or find / -name "*libv4l*" 2>/dev/null. It should succeed since your project B captures frames just fine. Then try to export found file to LD_PRELOAD.
If it won't succeed - check out your libv4l installation.
And make sure you trying to open() the correct camera which is not already in use.
I encountered a problem when I want to read an image using the OpenCV function imread().
The image is Ok and I can show it in the image display software.
But when I use the imdecode() to get the image data, the data returns NULL.
I will upload the image and the code and hope some one could help me
Mat img = imread(image_name);
if(!img.data) return -1;
The image's link is here: http://img3.douban.com/view/photo/raw/public/p2198361185.jpg
PS: The image_name is all right.
I guess OpenCV cannot decode this image. So is there any way to decode this image using OpenCV?, like add new decode library. By the way, I can read this image using other image library such as freeImage.
Your image is in .gif and it is not supported by OpenCV as of now.
Note OpenCV offers support for the image formats Windows bitmap (bmp),
portable image formats (pbm, pgm, ppm) and Sun raster (sr, ras). With
help of plugins (you need to specify to use them if you build yourself
the library, nevertheless in the packages we ship present by default)
you may also load image formats like JPEG (jpeg, jpg, jpe), JPEG 2000
(jp2 - codenamed in the CMake as Jasper), TIFF files (tiff, tif) and
portable network graphics (png). Furthermore, OpenEXR is also a
possibility.
Source - Click here
You can use something like this, to perform the conversion.
I was able to load your image using imread using this. Also, you can check out FreeImage.
You can also try to use the library gif2numpy. It converts a gif image to a numpy image which then can be loaded by OpenCV:
import cv2, gif2numpy
np_images, extensions, image_specs = gif2numpy.convert("yourgifimage.gif")
cv2.imshow("np_image", np_images[0])
cv2.waitKey()
The library can be found here: https://github.com/bunkahle/gif2numpy It is not dependent on PIL or pillow for this like imageio.
There are two methods to read an image in OpenCV, one is using Mat the other one using IplImage. I see you have used the former one. You can try with the second argument of imread also:
image = imread("image.jpg", CV_LOAD_IMAGE_COLOR); // Read the file
else use IplImage
#include "opencv2/highgui/highgui.hpp"
#include "opencv2/imgproc/imgproc_c.h"
#include <opencv2/core/core.hpp>
IplImage* src = 0;
if( (src = cvLoadImage("filename.jpg",1)) == 0 )
{
printf("Cannot load file image %s\n", filename);
}
If they don't work please check if you have installed libjpeg, libtiff and other dependencies for reading an image in OpenCV.
Hope it would help.
It had to happen, I'm stuck in the last phase of my project, when I want to use my code which works like a charm on my webcam, on an IP camera. The URL works perfectly in my browser, but nothing comes out with OpenCV...
Here is my code:
#include <opencv/highgui.h>
using namespace cv;
int main(int argc, char *argv[])
{
Mat frame;
namedWindow("video", 1);
VideoCapture cap("http://192.168.1.99:99/videostream.cgi?resolution=32&rate=0&user=admin&pwd=password&.mjpg");
while ( cap.isOpened() )
{
cap >> frame;
if(frame.empty()) break;
imshow("video", frame);
if(waitKey(30) >= 0) break;
}
return 0;
}
And the compiler settings :
//Added to the .pro file of QtCreator
INCLUDEPATH += C:\\OpenCV243\\release\\include
LIBS += -LC:\\OpenCV243\\release\\lib \
-lopencv_core243.dll \
-lopencv_highgui243.dll
I've tested opening a .avi file with the same code and it works... But a public IP camera URL like http://66.184.211.231/mjpg/video.mjpg doesn't ! What's the matter then ?
Removed by edit: I had considered FFMPEG to be an issue, but v2.4.3. has built-in FFMPEG support and .avi files work although I don't have any FFMPEG library installed (care to explain?)
Thanks in advance,
Regards,
Mister Mystère
Solved it by copying opencv_ffmpeg.dll from the build\x86\mingw\bin folder of the sources and pasting it next to built DLLs (bin folder accessible through PATH): I have no idea why, but the opencv_ffmpeg_64.dll had been produced instead.
Since you can connect and grab frames from a web camera I think that your library is set up correctly and you should be able to connect to IP cameras. I believe that the issue is with the supplied URL address of the camera.
Try logging into the camera and disable its password protection. Remove login and password fields from the URL, so it'll be something like "http://192.168.1.99:99/videostream.cgi?resolution=32&.mjpg". Also, you can log into the camera and check it's resolution. I noticed you have resolution=32 but I think it should be something like resolution=704x480.
Hope this helps.