I've been writing a program and every time I close my form it throws an exception saying my stack overflowed on the line which closes the background worker...
I have faced this problem for some time now, I've tried googling the problem but I haven't come up with any desired solution yet...
My troubleshooting guesses are as follows :
Pictures in picturebox takes up resources and are not cleared when aborting program
Background Worker is still busy
Here is my code, thanks in advance !
Elements
Picturebox called videobox
Button called btnOpenCamera_Click
Button called btnCloseCamera_Click
Label called backgroundworkerStatus
Variables
Global
Mat videoFrame;
VideoCapture video(0);
Private
bool flag_cameraStatus = true;
bool flag_backgroundworkerStatus = false;
Functions
private: System::Void MainForm_FormClosing
// this event is triggered when application is closing
video.release();
/* Exception is thrown here "System.StackOverflowException" */
backgroundWorker->CancelAsync();
if (backgroundWorker->IsBusy == false) {
checkBackgroundworkerStatus();
this->Close();
}
else {
MessageBox::Show("Backgroundworker not aborted");
e->Cancel = true;
}
private: System::Void btnOpenCamera_Click
// this is a button for turning on camera
flag_cameraStatus = true;
backgroundWorker->RunWorkerAsync();
private: System::Void btnCloseCamera_Click
// this is a button for turning off camera
flag_cameraStatus = false;
videoBox->Image = nullptr;
int openCamera()
// this is a button for turning off camera
if (!video.isOpened()) {
MessageBox::Show("Cannot Find Camera!");
return -1;
}
while (flag_camera) {
video >> videoFrame;
if (videoFrame.empty()) {
break;
}
/* These lines of code converts Opencv mat to bitmap for picturebox to display */
System::Drawing::Graphics^ graphics = videoBox->CreateGraphics();
System::IntPtr ptr(videoFrame.ptr());
System::Drawing::Bitmap^ b = gcnew System::Drawing::Bitmap(videoFrame.cols, videoFrame.rows, videoFrame.step, System::Drawing::Imaging::PixelFormat::Format24bppRgb, ptr);
System::Drawing::RectangleF rect(0, 0, videoBox->Width, videoBox->Height);
graphics->DrawImage(b, rect);
/* Was wondering if I need these lines of code below */
/* delete graphics; */
if (flag_camera == false) {
videoBox->Image = nullptr;
return 0;
}
void checkBackgroundworkerStatus()
// this function is used to check if backgroundworker is busy
// it will identify the status via the backcolor of label backgroundworkerStatus
if(backgroundWorker->IsBusy==true)
backgroundworkerStatus->BackColor = Color::Green;
else
backgroundworkerStatus->BackColor = SystemColors::Control;
private: System::Void backgroundWorker_DoWork
// this event is triggered when background worker is working
if (backgroundWorker->CancellationPending == false) {
checkBackgroundworkerStatus();
openCamera();
}
else {
this->backgroundWorker->CancelAsync();
}
private: System::Void backgroundWorker_RunWorkerCompleted
// this event is triggered when background worker is done working
checkBackgroundworkerStatus();
Some Last Notes...
I did set my
WorkerSupportsCancellation = true
WorkerReportsProgress = true
To solve this problem,add a delay to DoWork
private: System::Void backgroundWorker1_DoWork
using namespace System::Threading
/* your DoWork tasks */
Thread::Sleep(50)
Note
Thread::Sleep counts in milliseconds, you can change to the number you want according to your cameras fps.
My laptop webcam is approx. 15 fps, which is 66.66 ms per frames, the sleep time should be >= this ms/frame but I have no problems running it with a delay of only 50ms.
Related
I try to make frame grabber class from IP Camera using std::queue and opencv
In this class, It takes and store maximum 10 frame,
and Other class, get frame from buffer.
/* Camera.cpp */
struct FRAME
{
cv::Mat Img;
uint64_t Time;
bool ReadError;
};
class Camera
{
std::queue<FRAME> m_buffer;
std::mutex m_buffer_mutex;
...
};
void Camera::threadFunc_get_stream_from_camera()
{
while (true)
{
FRAME frame;
... // read sequence (if cv::read is fail, store frame routine is skipping)
m_buffer_mutex.lock();
while (m_buffer.size() >= 10)
m_buffer.pop();
m_buffer.push(frame);
m_buffer_mutex.unlock();
}
}
FRAME Camera::grab()
{
std::unique_lock ulock(m_buffer_mutex);
FRAME frame;
if (m_buffer.empty() == false)
{
frame = m_buffer.front();
m_buffer.pop();
return frame;
}
}
/***************/
/* Testing.cpp */
int main()
{
// Camera* cam ..
...
while (true)
{
auto frame = cam->grab();
if (frame.Img.data == nullptr || frame.Time == 0)
continue;
... // frame image processing
}
}
I kept the program this way for about 3 days, and no special bugs or memory sticks were found.
But the reason I'm asking this question is,
whether it's right to use non-pointer(FRAME) in grab() function.
I'm using C++17, and I think there is no problem because the uint64_t or bool values in the structure are copied in this version.
but, How about cv::Mat ?
I don't want to using Producer-Consumer pattern, because not want to contain testing class side's code in Camera class.
I am using EmguCV to create a capture from a video file stored on disk. I set the capture property for frame position and then perform a QueryFrame. On certain frames from the video, when I go to process the Mat further I get the error '{"OpenCV: Unrecognized or unsupported array type"}'. This doesn't happen on all frames of the video but when I run it for the same video it happens for the same frames in the video. If I save the Mat to disk the image looks perfectly fine and saves without error. Here is the code for loading and processing the image:
Capture cap = new Capture(movieLocation);
int framePos = 0;
while (reading)
{
cap.SetCaptureProperty(CapProp.PosFrames, framePos);
using (var frame = cap.QueryFrame())
{
if (frame != null)
{
try
{
var fm = Rotate(frame); // Works fine
// Other Processing including classifier.DetectMultiScale -- Error occurs here
frameMap.Add(framePos, r);
}
catch (Exception ex)
{
var s = ""; // Done to just see the error
}
framePos = framePos + 2;
}
else
{
reading = false;
}
}
}
Line of code which throws exception in further processing
var r = _classifier.DetectMultiScale(matIn, 1.1, 2, new Size(200, 200), new Size(375, 375));
As I said, this does not fail for every frame of the video.
I'm trying to solve this because sometimes it skips 1 frame but at other times it will skip whole blocks of frames which is causing me to miss important events in the video.
After a bit more working on it, I figured out that the Mat had a ROI set on it before going to the cascade classifier. In the instances where the mat was failing the ROI was set to 0 height and 0 width. This caused the issue.
I have two styles of interactions, one highlights the feature, the second places a tooltop with the feature name. Commenting both out, they're very fast, leave either in, the map application slows in IE and Firefox (but not Chrome).
map.addInteraction(new ol.interaction.Select({
condition: ol.events.condition.pointerMove,
layers: [stationLayer],
style: null // this is actually a style function but even as null it slows
}));
$(map.getViewport()).on('mousemove', function(evt) {
if(!dragging) {
var pixel = map.getEventPixel(evt.originalEvent);
var feature = null;
// this block directly below is the offending function, comment it out and it works fine
map.forEachFeatureAtPixel(pixel, function(f, l) {
if(f.get("type") === "station") {
feature = f;
}
});
// commenting out just below (getting the feature but doing nothing with it, still slow
if(feature) {
target.css("cursor", "pointer");
$("#FeatureTooltip").html(feature.get("name"))
.css({
top: pixel[1]-10,
left: pixel[0]+15
}).show();
} else {
target.css("cursor", "");
$("#FeatureTooltip").hide();
}
}
});
I mean this seems like an issue with OpenLayers-3 but I just wanted to be sure I wasn't overlooking something else here.
Oh yeah, there's roughly 600+ points. Which is a lot, but not unreasonably so I would think. Zooming-in to limit the features in view definitely helps. So I guess this is a # of features issue.
This is a known bug and needs more investigation. You can track progress here: https://github.com/openlayers/ol3/issues/4232.
However, there is one thing you can do to make things faster: return a truthy value from map.forEachFeatureAtPixel to stop checking for features once one was found:
var feature = map.forEachFeatureAtPixel(pixel, function(f) {
if (f.get('type') == 'station') {
return feature;
}
});
i had same issue, solved a problem by setInterval, about this later
1) every mouse move to 1 pixel fires event, and you will have a quee of event till you stop moving, and the quee will run in calback function, and freezes
2) if you have an objects with difficult styles, all element shown in canvas will take time to calculate for if they hit the cursor
resolve:
1. use setInterval
2. check for pixels moved size from preview, if less than N, return
3. for layers where multiple styles, try to simplify them by dividing into multiple ones, and let only one layer by interactive for cursor move
function mouseMove(evt) {
clearTimeout(mm.sheduled);
function squareDist(coord1, coord2) {
var dx = coord1[0] - coord2[0];
var dy = coord1[1] - coord2[1];
return dx * dx + dy * dy;
}
if (mm.isActive === false) {
map.unByKey(mm.listener);
return;
}
//shedules FIFO, last pixel processed after 200msec last process
const elapsed = (performance.now() - mm.finishTime);
const pixel = evt.pixel;
const distance = squareDist(mm.lastP, pixel);
if (distance > 0) {
mm.lastP = pixel;
mm.finishTime = performance.now();
mm.sheduled = setTimeout(function () {
mouseMove(evt);
}, MIN_ELAPSE_MSEC);
return;
} else if (elapsed < MIN_ELAPSE_MSEC || mm.working === true) {
// console.log(`distance = ${distance} and elapsed = ${elapsed} mesc , it never should happen`);
mm.sheduled = setTimeout(function () {
mouseMove(evt);
}, MIN_ELAPSE_MSEC);
return;
}
//while multithreading is not working on browsers, this flag is unusable
mm.working = true;
let t = performance.now();
//region drag map
const vStyle = map.getViewport().style;
vStyle.cursor = 'default';
if (evt.dragging) {
vStyle.cursor = 'grabbing';
}//endregion
else {
//todo replace calback with cursor=wait,cursor=busy
UtGeo.doInCallback(function () {
checkPixel(pixel);
});
}
mm.finishTime = performance.now();
mm.working = false;
console.log('mm finished', performance.now() - t);
}
In addition to #ahocevar's answer, a possible optimization for you is to utilize the select interaction's select event.
It appears that both the select interaction and your mousemove listener are both checking for hits on the same layers, doing double work. The select interaction will trigger select events whenever the set of selected features changes. You could listen to it, and show the popup whenever some feature is selected and hide it when not.
This should reduce the work by half, assuming that forEachFeatureAtPixel is what's hogging the system.
I want to draw a line using mouse-event in Opencv in a webcam frame. I also want to erase it just like an eraser in MS-Paint.How can i do it? I dont have much idea about it. But i have this scrambled pseduo code from my head which can be completely wrong but i will write it down anyway. I would like to know how to implement it in c++.
So, i will have two three mouse event-
event 1- Mouse leftbuttonup-- this will be used to start the drawing
event 2- Mouse move -- this will be used to move the mouse to draw
event 3:- Mouse leftbuttondown-this will be used to stop the drawing.
event 4- Mouse double click - this event i can use to erase the drawing.
I will also have a drawfunction for a line such as line(Mat image,Point(startx,starty),Point(endx,endy),(0,0,255),1));
Now, i dont know how to implement this in a code format. I tried a lot but i get wrong results. I have a sincere request that please suggest me the code in Mat format not the Iplimage format. Thanks.
please find working code below with inlined explained comments using Mat ;)
Let me know in case of any problem.
PS: In main function, I have changed defauld cam id to 1 for my code, you should keep it suitable for you PC, probably 0. Good Luck.
#include <iostream>
#include <opencv\cv.h>
#include <opencv2\core\core.hpp>
#include <opencv2\highgui\highgui.hpp>
class WebCamPaint
{
public:
int cam_id;
std::string win_name;
cv::VideoCapture webCam;
cv::Size frame_size;
cv::Mat cam_frame, drawing_canvas;
cv::Point current_pointer, last_pointer;
cv::Scalar erase_color, paint_color;
int pointer_size;
//! Contructor to initialize basic members to defaults
WebCamPaint()
{
cam_id = 0;
pointer_size = 5;
win_name = std::string("CamView");
current_pointer = last_pointer = cv::Point(0, 0);
erase_color = cv::Scalar(0, 0, 0);
paint_color = cv::Scalar(250, 10, 10);
}
//! init function is required to set some members in case default members needed to change.
bool init()
{
//! Opening cam with specified cam id
webCam.open(cam_id);
//! Check if problem opening video
if (!webCam.isOpened())
{
return false;
}
//! Reading single frame and extracting properties
webCam >> cam_frame;
//! Check if problem reading video
if (cam_frame.empty())
{
return false;
}
frame_size = cam_frame.size();
drawing_canvas = cv::Mat(frame_size, CV_8UC3);
//! Creating Activity / Interface window
cv::namedWindow(win_name);
cv::imshow(win_name, cam_frame);
//! Resetting drawing canvas
drawing_canvas = erase_color;
//! initialization went successful ;)
return true;
}
//! This function deals wih all processing, drawing and displaying ie main UI to user
void startAcivity()
{
//! Keep doing until user presses "Esc" from Keyboard, wait for 20ms for user input
for (char user_input = cv::waitKey(20); user_input != 27; user_input = cv::waitKey(20))
{
webCam >> cam_frame; //Read a frame from webcam
cam_frame |= drawing_canvas; //Merge with actual drawing canvas or drawing pad, try different operation to merge incase you want different effect or solid effect
cv::imshow(win_name, cam_frame); //Display the image to user
//! Change size of pointer using keyboard + / -, don't they sound fun ;)
if (user_input == '+' && pointer_size < 25)
{
pointer_size++;
}
else if (user_input == '-' && pointer_size > 1)
{
pointer_size--;
}
}
}
//! Our function that should be registered in main to opencv Mouse Event Callback
static void onMouseCallback(int event, int x, int y, int flags, void* userdata)
{
/* NOTE: As it will be registered as mouse callback function, so this function will be called if anything happens with mouse
* event : mouse button event
* x, y : position of mouse-pointer relative to the window
* flags : current status of mouse button ie if left / right / middle button is down
* userdata: pointer o any data that can be supplied at time of setting callback,
* we are using here to tell this static function about the this / object pointer at which it should operate
*/
WebCamPaint *object = (WebCamPaint*)userdata;
object->last_pointer = object->current_pointer;
object->current_pointer = cv::Point(x, y);
//! Drawing a line on drawing canvas if left button is down
if (event == 1 || flags == 1)
{
cv::line(object->drawing_canvas, object->last_pointer, object->current_pointer, object->paint_color, object->pointer_size);
}
//! Drawing a line on drawing canvas if right button is down
if (event == 2 || flags == 2)
{
cv::line(object->drawing_canvas, object->last_pointer, object->current_pointer, object->erase_color, object->pointer_size);
}
}
};
int main(int argc, char *argv[])
{
WebCamPaint myCam;
myCam.cam_id = 1;
myCam.init();
cv::setMouseCallback(myCam.win_name, WebCamPaint::onMouseCallback, &myCam);
myCam.startAcivity();
return 0;
}
I'm working on a windows phone 7 project, with silverlight, and i'm trying to show 4 images in sequence to give the user the feeling of a short movie.
I have 4 urls pointing to 4 different jpeg images, and I'm using an Image control to show these jpeg in sequence.
The way I'm trying to achieve this is by doing:
private void RetrieveImages()
{
image1.ImageOpened += new EventHandler<RoutedEventArgs>(image1_ImageOpened);
frameNumber = 0;
gotoNextImage();
}
void image1_ImageOpened(object sender, RoutedEventArgs e)
{
System.Threading.Thread.Sleep(400);
gotoNextImage();
}
private void gotoNextImage()
{
if (frameNumber < 4)
{
webBrowser1.Dispatcher.BeginInvoke(()=> {
image1.Source = new System.Windows.Media.Imaging.BitmapImage(new Uri(cam.framesUrl[frameNumber]));
frameNumber++;
});
}
else
{
image1.ImageOpened -= image1_ImageOpened;
}
}
But this just don't work as expected. I'm sure I'm missing something about how to interact with the UI.
Can anyone point me in the right direction?
Which is the best way to achieve this?
Edited:
I'll explain better what's wrong with my code... probably it's unclear what happens.
I don't get any error with my code, but I don't see the "movie effect" too. It just show 1 single image, without iterating between the image collection.
I think it's a threading problem... kind of I'm not doing the right thing in the right thread to see the UI updating as expected...
This seams to work best.
xaml
<UserControl
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
mc:Ignorable="d"
x:Class="YourNamspace.YourClass"
d:DesignWidth="24"
d:DesignHeight="24">
<Grid x:Name="LayoutRoot">
<Image Name="YourImageName" Stretch="Fill" Source="YourPath" ImageOpened="onImageOpened"/>
</Grid>
</UserControl>
C#
using System;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Documents;
using System.Windows.Ink;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Imaging;
using System.Windows.Media.Animation;
using System.Windows.Shapes;
using System.Threading;
namespace YourNameSpace
{
public partial class YourClass : UserControl
{
public int FirstImageIndex = 1;
public int LastImageIndex = 1000;
public int CurrentImageIndex = 1;
public YourClass()
{
InitializeComponent();
}
private void onImageOpened(object sender, System.Windows.RoutedEventArgs e)
{
Thread.Sleep(1000);
CurrentImageIndex = ( CurrentImageIndex == LastImageIndex ) ? FirstImageIndex : CurrentImageIndex++;
YourImageName.Source = new BitmapImage(new Uri("Your/path/to/image"+CurrentImageIndex+".jpg"), UriKind.RelativeOrAbsolute);
}
}
}
Hope that helps. I am pretty new to Silverlight.
So far the best way is to define the image as a resource. Via converter setting the image source.
But, your code should work fine as well. Try setting UriKind.RelativeOrAbsolute may be that should help. Because, this is the most common area while setting image source causes issue
HTH
Ok, I figured it out, and I think I also find a nice solution :) IMHO
I basically bound the Image.source to a proprerty of my class (that now extends INotifyPropertyChanged). But this gave me some issue about the transiction between images: since they were downloaded from internet there was a black images occurring between one images an the next one... but only the first time (i'm looping on a set of 4 images, looks like the video repeat), 'cause after that the images are cached.
So, what I've done is to cache the images the first time, without displaying the right Image control, but displaying instead another Image control (or whatever else) which says to the user "I'm loading".
For handle this scenario I've created a custom event:
public delegate void FramesPrefetchedEventHanlder();
public event FramesPrefetchedEventHanlder FramesPrefetched;
Now let's take a look at the RetrieveImages method:
private void RetrieveImages()
{
frameNumber = 0;
currentCycle = 0;
// set e very short interval, used for prefetching frames images
timer.Interval = new TimeSpan(0, 0, 0, 0, 10);
timer.Tick += (sender, e) => gotoNextImage();
// defines what is going to happen when the prefetching is done
this.FramesPrefetched += () =>
{
// hide the "wait" image and show the "movie" one
imageLoading.Opacity = 0;
image1.Opacity = 1;
// set the timer with a proper interval to render like a short movie
timer.Interval = new TimeSpan(0, 0, 0, 0, 400);
};
// when a frame is loaded in the main Image control, the timer restart
image1.ImageOpened += (s, e) =>
{
if (currentCycle <= cycles) timer.Start();
};
// start the loading (and showing) frames images process
gotoNextImage();
}
Ok, now what we need to handle is the step by step loading of the image and communicate when we finished the prefetching phase:
private void gotoNextImage()
{
timer.Stop();
if (frameNumber < 4)
{
CurrentFrame = new System.Windows.Media.Imaging.BitmapImage(new Uri(cam.framesUrl[frameNumber]));
frameNumber++;
}
else
{
// repeat the frame's sequence for maxCycles times
if (currentCycle < maxCycles)
{
frameNumber = 0;
currentCycle++;
// after the first cycle through the frames, raise the FramesPrefetched event
if (currentCycle == 1)
{
FramesPrefetchedEventHanlder handler = FramesPrefetched;
if (handler != null) handler();
}
// step over to next frame
gotoNextImage();
}
}
}
This works pretty fine to me... but since I'm new to Silverlight and Windows Phone 7 developement, any suggestion for improvement is welcome.