The following code takes a snapshot of part of the screen (at the mouse coordinates) and should display it in an Image control.
public partial class MainWindow : Window
{
Timer timer = new Timer(100);
public MainWindow()
{
InitializeComponent();
timer.Elapsed += Timer_Elapsed;
timer.Start();
}
[System.Runtime.InteropServices.DllImport("gdi32.dll")]
public static extern bool DeleteObject(IntPtr hObject);
private void Timer_Elapsed(object sender, ElapsedEventArgs e)
{
viewerImage.Source = GetSnapAtMouseCoords((int)((Grid)viewerImage.Parent).ActualWidth, (int)((Grid)viewerImage.Parent).ActualHeight, System.Windows.Forms.Cursor.Position);
}
private BitmapSource GetSnapAtMouseCoords(int width, int height, System.Drawing.Point mousePosition)
{
IntPtr handle = IntPtr.Zero;
try
{
using (var screenBmp = new Bitmap(width, height, System.Drawing.Imaging.PixelFormat.Format32bppArgb))
{
using (var bmpGraphics = Graphics.FromImage(screenBmp))
{
bmpGraphics.CopyFromScreen(mousePosition.X, mousePosition.Y, 0, 0, screenBmp.Size);
handle = screenBmp.GetHbitmap();
var bs = System.Windows.Interop.Imaging.CreateBitmapSourceFromHBitmap(
handle,
IntPtr.Zero,
Int32Rect.Empty,
BitmapSizeOptions.FromEmptyOptions());
return bs;
}
}
}
finally
{
DeleteObject(handle);
}
}
}
Everything works up to the point where I set the image source to the BitmapSource. Unfortunately, the image is never rendered on screen.
I think that maybe this is because I am creating the BitmapSource on the GUI thread... But I am not so sure.
Any suggestions or ideas welcome.
Actually it's because you are accessing your GUI on a different Thread. You can either wrap the initial call like this:
Dispatcher.BeginInvoke(new Action(() =>
{
viewerImage.Source = GetSnapAtMouseCoords(
(int)((Grid)viewerImage.Parent).ActualWidth,
(int)((Grid)viewerImage.Parent).ActualHeight,
System.Windows.Forms.Cursor.Position);
}));
Or do all the processing in a background thread an just return a Frozen (Thread safe) BitmapSource. You would hover need to pass (int)((Grid)viewerImage.Parent).ActualWidth differently, since that is owned by the UI thread too.
bs.Freeze();
Dispatcher.BeginInvoke(new Action(() =>
{
viewerImage.Source = bs;
}));
Related
I have a WPF application, and am streaming a camera frame from an opencv DLL into an Image control inside a UserControl.
This works for a while, and then crashes, giving me:
The calling thread cannot access this object because a different thread owns it.
My code is as follows:
The class that calls the image: (running in a thread)
private void imageShow()
{
while (true)
{
if (status == 1)
{
IntPtr ptr = getFrame(); // The DLL function that returns the image.
imgHalfSize = new Bitmap(640, 360, 3 * 640, PixelFormat.Format24bppRgb, ptr);
CameraFrame = ToBitmapSource(imgHalfSize);
CameraFrame.Freeze();
Thread.Sleep(20);
}
}
//conversion from Bitmap to BitmapSource
public BitmapSource CameraFrame;
[DllImport("gdi32")]
private static extern int DeleteObject(IntPtr o);
public static BitmapSource ToBitmapSource(Bitmap source)
{
IntPtr ptr = source.GetHbitmap(); //obtain the Hbitmap
BitmapSource bs = System.Windows.Interop.Imaging.CreateBitmapSourceFromHBitmap(
ptr,
IntPtr.Zero,
Int32Rect.Empty,
System.Windows.Media.Imaging.BitmapSizeOptions.FromEmptyOptions());
DeleteObject(ptr); //release the HBitmap
return bs;
}
//The userControl that displays the image:
//xaml
<Image Name="ImageCameraFrame"/>
cs:
public FormCameraViewFull(DllFunctions _Dense)
{
Dense = _Dense; // The class as above
InitializeComponent();
Task.Factory.StartNew(() =>
{
InvokeMethodExample();
});
}
//thread function:
private void InvokeMethodExample()
{
while (true)
{
ImageCameraFrame.Dispatcher.Invoke((Action)(() => ImageCameraFrame.Source = Dense.CameraFrame));
}
}
As above, this works great for some time, then crashes. I was under the impression that the line CameraFrame.Freeze(); should stop this behavior, but I am clearly doing something wrong. Do I need a mutex, or similar lock here?
Thank you.
Use a DispatcherTimer with (an optionally async) Tick handler:
var timer = new DispatcherTimer
{
Interval = TimeSpan.FromMilliseconds(50)
};
timer.Tick += async (s, e) =>
{
ImageCameraFrame.Source = await Task.Run(() =>
{
var data = Dense.getFrame();
var format = PixelFormats.Rgb24;
var width = 640;
var height = 360;
var stride = (width * format.BitsPerPixel + 7) / 8;
var bitmap = BitmapSource.Create(width, height, 96, 96,
format, null, data, stride * height, stride);
bitmap.Freeze();
return bitmap;
});
};
timer.Start();
Task: I got 2 monitors. And I need to show on #1 what is going on #2. In another words, first monitor is nothing but a reflector of second.
Current solution: Just making screenshot every ~100ms and re-render.
Following method is responsible for capturing screenshots:
private BitmapSource MakeScreenshot(Screen screen)
{
using (var screenBmp = new Bitmap(screen.Bounds.Width, screen.Bounds.Height, PixelFormat.Format32bppArgb))
{
using (var bmpGraphics = Graphics.FromImage(screenBmp))
{
bmpGraphics.CopyFromScreen(screen.Bounds.X, screen.Bounds.Y, 0, 0, screen.Bounds.Size);
return
Imaging.CreateBitmapSourceFromHBitmap(
screenBmp.GetHbitmap(),
IntPtr.Zero,
Int32Rect.Empty,
BitmapSizeOptions.FromEmptyOptions());
}
}
}
After that I uset Start(...) method to run my "reflection" from second screen to first:
public void Start(int delay, int period)
{
if (_timer != null) throw new InvalidOperationException();
_timer = new System.Threading.Timer(
_ =>
{
_placeholder
.Dispatcher
.Invoke(() =>
{
_placeholder.Source = MakeScreenshot(_targetScreen); // re-render new screenshot
});
},
null,
delay,
period);
}
Problem: After around 30-40 second of pretty nice run it fails with OutOfMemoryException. I've investigated some of posts here, but found nothing regarding my problem.
That is because you leak memory here:
Imaging.CreateBitmapSourceFromHBitmap(
screenBmp.GetHbitmap(), // < here
IntPtr.Zero,
Int32Rect.Empty,
BitmapSizeOptions.FromEmptyOptions());
You need to free memory used by GDI bitmap after you call screenBmp.GetHbitmap(). Change that like this:
private BitmapSource MakeScreenshot(Screen screen)
{
using (var screenBmp = new Bitmap(screen.Bounds.Width, screen.Bounds.Height, PixelFormat.Format32bppArgb))
{
using (var bmpGraphics = Graphics.FromImage(screenBmp))
{
bmpGraphics.CopyFromScreen(screen.Bounds.X, screen.Bounds.Y, 0, 0, screen.Bounds.Size);
var handle = screenBmp.GetHbitmap();
try {
return
Imaging.CreateBitmapSourceFromHBitmap(
handle,
IntPtr.Zero,
Int32Rect.Empty,
BitmapSizeOptions.FromEmptyOptions());
}
finally {
DeleteObject(handle);
}
}
}
}
[System.Runtime.InteropServices.DllImport("gdi32.dll")]
public static extern bool DeleteObject(IntPtr hObject);
And it should not leak any more.
I am receiving video from kinect device. Server is sending video frame by frame and on the client side it receives frame but starts flickering on image control if I use BitmapSource. Create function which is responsible of increasing CPU usage after that i use WriteableBitmap class but I'm stuck into a new problem, it is giving me error "the calling thread cannot access the object but different thread own it", i use dispather.invoke to solve the problem but it is giving me the same error.
public partial class MainWindow : Window
{
TcpClient client;
NetworkStream ns;
Thread vedioframe;
WriteableBitmap vediofram = null;
public MainWindow()
{
InitializeComponent();
client = new TcpClient();
client.Connect("127.0.0.1", 9000);
vedioframe = new Thread(Display_Frame);
vedioframe.Start();
}
public void Display_Frame()
{
ns = client.GetStream();
while (true)
{
byte[] vedio = new byte[1228800];
ns.Read(vedio, 0, vedio.Length);
try
{
if (vediofram == null)
{
vediofram = new WriteableBitmap(640, 480, 96, 96, PixelFormats.Bgr32, null);
}
else
{
vediofram.WritePixels(new Int32Rect(0, 0, 640, 480), vedio, 640 * 4, 0);
}
Update_Frame(vediofram);
}
catch (Exception e)
{
MessageBox.Show(e.Message);
}
// Dispatcher.Invoke(new Action(() => { BitmapSource s = BitmapSource.Create(640, 480, 96, 96, PixelFormats.Bgr32, null, vedio, 640 * 4);
// Vedio.Source = s;
/// }));
}
}
void Update_Frame(WriteableBitmap src)
{
Dispatcher.Invoke(new Action(() => { Vedio.Source = src; }));
}
}
The problem is that you're creating the WriteableBitmap in your background thread. It needs to be created on the UI thread, and you would want to pass the data to the UI thread to update the bitmap.
The first answer to Asynchronous operations on WriteableBitmap elaborates further.
I am trying to capture the following page using standard c# .net code. I've searched around for people's various methods, most of which involve instantiating a browser object and using a draw to bitmap method. However, none of these pick up the contents of the chart on this page:
http://www.highcharts.com/demo/combo-dual-axes
Perhaps the javascript doesn't have time to run, but adding Thread.Sleep(x) hasn't assisted.
This commercial component captures it correctly, but I'd rather avoid requiring an additional dependency in my project and paying $150 when the other solutions are sooo close!.
Anyone find their solution renders this correctly?
You have possibly tried IECapt. I think it is the right way to go. I created a modified version of it and use a timer instead of Thread.Sleep it captures your site as expected.
------EDIT------
Here is the ugly source. Just Add a reference to Microsoft HTML Object Library.
And this is the usage:
HtmlCapture capture = new HtmlCapture(#"c:\temp\myimg.png");
capture.HtmlImageCapture += new HtmlCapture.HtmlCaptureEvent(capture_HtmlImageCapture);
capture.Create("http://www.highcharts.com/demo/combo-dual-axes");
void capture_HtmlImageCapture(object sender, Uri url)
{
this.Close();
}
File1
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;
using System.IO;
namespace MyIECapt
{
public class HtmlCapture
{
private WebBrowser web;
private Timer tready;
private Rectangle screen;
private Size? imgsize = null;
//an event that triggers when the html document is captured
public delegate void HtmlCaptureEvent(object sender, Uri url);
public event HtmlCaptureEvent HtmlImageCapture;
string fileName = "";
//class constructor
public HtmlCapture(string fileName)
{
this.fileName = fileName;
//initialise the webbrowser and the timer
web = new WebBrowser();
tready = new Timer();
tready.Interval = 2000;
screen = Screen.PrimaryScreen.Bounds;
//set the webbrowser width and hight
web.Width = 1024; //screen.Width;
web.Height = 768; // screen.Height;
//suppress script errors and hide scroll bars
web.ScriptErrorsSuppressed = true;
web.ScrollBarsEnabled = false;
//attached events
web.Navigating +=
new WebBrowserNavigatingEventHandler(web_Navigating);
web.DocumentCompleted += new
WebBrowserDocumentCompletedEventHandler(web_DocumentCompleted);
tready.Tick += new EventHandler(tready_Tick);
}
public void Create(string url)
{
imgsize = null;
web.Navigate(url);
}
public void Create(string url, Size imgsz)
{
this.imgsize = imgsz;
web.Navigate(url);
}
void web_DocumentCompleted(object sender,
WebBrowserDocumentCompletedEventArgs e)
{
//start the timer
tready.Start();
}
void web_Navigating(object sender, WebBrowserNavigatingEventArgs e)
{
//stop the timer
tready.Stop();
}
void tready_Tick(object sender, EventArgs e)
{
try
{
//stop the timer
tready.Stop();
mshtml.IHTMLDocument2 docs2 = (mshtml.IHTMLDocument2)web.Document.DomDocument;
mshtml.IHTMLDocument3 docs3 = (mshtml.IHTMLDocument3)web.Document.DomDocument;
mshtml.IHTMLElement2 body2 = (mshtml.IHTMLElement2)docs2.body;
mshtml.IHTMLElement2 root2 = (mshtml.IHTMLElement2)docs3.documentElement;
// Determine dimensions for the image; we could add minWidth here
// to ensure that we get closer to the minimal width (the width
// computed might be a few pixels less than what we want).
int width = Math.Max(body2.scrollWidth, root2.scrollWidth);
int height = Math.Max(root2.scrollHeight, body2.scrollHeight);
//get the size of the document's body
Rectangle docRectangle = new Rectangle(0, 0, width, height);
web.Width = docRectangle.Width;
web.Height = docRectangle.Height;
//if the imgsize is null, the size of the image will
//be the same as the size of webbrowser object
//otherwise set the image size to imgsize
Rectangle imgRectangle;
if (imgsize == null) imgRectangle = docRectangle;
else imgRectangle = new Rectangle() { Location = new Point(0, 0), Size = imgsize.Value };
//create a bitmap object
Bitmap bitmap = new Bitmap(imgRectangle.Width, imgRectangle.Height);
//get the viewobject of the WebBrowser
IViewObject ivo = web.Document.DomDocument as IViewObject;
using (Graphics g = Graphics.FromImage(bitmap))
{
//get the handle to the device context and draw
IntPtr hdc = g.GetHdc();
ivo.Draw(1, -1, IntPtr.Zero, IntPtr.Zero,
IntPtr.Zero, hdc, ref imgRectangle,
ref docRectangle, IntPtr.Zero, 0);
g.ReleaseHdc(hdc);
}
//invoke the HtmlImageCapture event
bitmap.Save(fileName);
bitmap.Dispose();
}
catch
{
//System.Diagnostics.Process.GetCurrentProcess().Kill();
}
if(HtmlImageCapture!=null) HtmlImageCapture(this, web.Url);
}
}
}
and File2
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Drawing;
using System.Runtime.InteropServices;
namespace MyIECapt
{
[ComVisible(true), ComImport()]
[GuidAttribute("0000010d-0000-0000-C000-000000000046")]
[InterfaceTypeAttribute(ComInterfaceType.InterfaceIsIUnknown)]
public interface IViewObject
{
[return: MarshalAs(UnmanagedType.I4)]
[PreserveSig]
int Draw(
[MarshalAs(UnmanagedType.U4)] UInt32 dwDrawAspect,
int lindex,
IntPtr pvAspect,
[In] IntPtr ptd,
IntPtr hdcTargetDev,
IntPtr hdcDraw,
[MarshalAs(UnmanagedType.Struct)] ref Rectangle lprcBounds,
[MarshalAs(UnmanagedType.Struct)] ref Rectangle lprcWBounds,
IntPtr pfnContinue,
[MarshalAs(UnmanagedType.U4)] UInt32 dwContinue);
[PreserveSig]
int GetColorSet([In, MarshalAs(UnmanagedType.U4)] int dwDrawAspect,
int lindex, IntPtr pvAspect, [In] IntPtr ptd,
IntPtr hicTargetDev, [Out] IntPtr ppColorSet);
[PreserveSig]
int Freeze([In, MarshalAs(UnmanagedType.U4)] int dwDrawAspect,
int lindex, IntPtr pvAspect, [Out] IntPtr pdwFreeze);
[PreserveSig]
int Unfreeze([In, MarshalAs(UnmanagedType.U4)] int dwFreeze);
}
}
Thread.Sleep will simply suspend the thread your web browser is running on - how do you expect it to render anything when it is suspended? :)
Instead, you need to allow the thread to process work. You can achieve this with a combination of Thread.Sleep(0) and Application.DoEvents(), with something like the following:
DateTime finish = DateTime.Now.AddSeconds(3);
while (DateTime.Now < finish) {
Application.DoEvents();
Thread.Sleep(0);
}
#L.B , thank you for the help!
Just an FYI for anyone wanting to run it in a class library,
WebBrowser needs to Single Threaded Apartment, so do something like this:
var t = new Thread(InitAndDo); //InitAndDo would have your code creating the webbrowser object etc...
t.SetApartmentState(ApartmentState.STA);
t.Start();
Then the Gotcha, after the navigate call is done, add this line of code so that you get the completed navigation event:
web.Navigate(Url);
Application.Run();
I created a nuget package for this purpose
https://github.com/dcumin39/RenderHighCharts/wiki
I get this exception on that code.
How to fix it?
Excepton:
The calling thread cannot access this
object because a different thread owns
it.
Code:
void CamProc_NewTargetPosition(IntPoint Center, System.Drawing.Bitmap image)
{
IntPtr hBitMap = image.GetHbitmap();
BitmapSource bmaps = Imaging.CreateBitmapSourceFromHBitmap(hBitMap, IntPtr.Zero, Int32Rect.Empty, BitmapSizeOptions.FromEmptyOptions());
Dispatcher.BeginInvoke((Action)(() =>
{
labelX.Content = String.Format("X: {0}", Center.X); //OK Working
labelY.Content = String.Format("Y: {0}", Center.Y); //OK Working
pictureBoxMain.Source = bmaps; // THERE IS EXCEPTON
}), DispatcherPriority.Render, null);
}
pictureBoxMain is System.Windows.Controls.Image.
You can freeze the BitmapSource so that it can be accessed from any thread:
void CamProc_NewTargetPosition(IntPoint Center, System.Drawing.Bitmap image)
{
IntPtr hBitMap = image.GetHbitmap();
BitmapSource bmaps = Imaging.CreateBitmapSourceFromHBitmap(hBitMap, IntPtr.Zero, Int32Rect.Empty, BitmapSizeOptions.FromEmptyOptions());
bmaps.Freeze();
Dispatcher.BeginInvoke((Action)(() =>
{
labelX.Content = String.Format("X: {0}", Center.X);
labelY.Content = String.Format("Y: {0}", Center.Y);
pictureBoxMain.Source = bmaps;
}), DispatcherPriority.Render, null);
}
You could Freeze the image, as suggested in another thread, which gets rid of the threading restriction but makes the image immutable.
WPF/BackgroundWorker and BitmapSource problem