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Drawing characters to form at timer tick

I am trying to draw a character on the screen every 500 milliseconds but they won't appear on the screen
using System;
using System.Drawing;
using System.Windows.Forms;
public partial class Form4 : Form
{
public Form4()
{
InitializeComponent();
}
PictureBox pb;
Bitmap surface;
Graphics device;
Timer timer;
int num = 0;
string text = "This is a test";
char[] textChar;
Font font = new Font("Black Ops One", 20, FontStyle.Regular, GraphicsUnit.Pixel);
private void Form4_Load(object sender, EventArgs e)
{
//picture box
pb = new PictureBox();
pb.Parent = this;
pb.Dock = DockStyle.Fill;
pb.BackColor = Color.Black;
//create graphics device
surface = new Bitmap(this.Size.Width, this.Size.Height);
pb.Image = surface;
device = Graphics.FromImage(surface);
//set up timer
timer = new Timer();
timer.Interval = 500;
timer.Enabled = true;
timer.Tick += new System.EventHandler(TimerTick);
//mis
textChar = text.ToCharArray();
}
public void TimerTick(object sender, EventArgs e)
{
DrawText();
if (num > textChar.Length - 1)
{
timer.Enabled = false;
MessageBox.Show("have hit the end");
}
}
public void DrawText()
{
device.DrawString(textChar[num].ToString(), font, Brushes.Red, 10, 10 + num * 22)
num++;
}
}
I hope to have the form at the end have the string on the form, but have the characters come up one by one. The form won't show any of the text. It only shows a black background.

You need to make the bitmap the image of the picture box pb.Image = surface.
public void DrawText()
{
device.DrawString(textChar[num].ToString(), font, Brushes.Red, 10, 10 + num * 22)
num++;
pb.Image = surface;
}

Use a KeyDown inside a Timer_Tick Event

Me and my buddy have been working on this magnifier application and we cannot make it work the way we want it.
The way we would like it to work:
Open app.
Move mouse to area you want magnified.
Hit enter.
Magnifying window moves to (offset) location of mouse and keeps updating that window for that specific location.
Hit enter again to move window to new cursor location.
Right now once i hit enter, the window follows the mouse because it goes into a for loop where it grabs "Cursor.Position". I've tried to save the Cursor.Position value at the "OnkeyDown" event and use it inside the timer loop but that won't work since it "does not exist in current context".
Can anyone see how i can do this?
Thanks in advance!
/Morten
/* O-button zooms out
* I-button zooms in
* Esc-button exits app
* Enter moves magnifying window to new location (doesn't work)
*/
using System;
using System.Drawing;
using System.Windows.Forms;
namespace Magnifier
{
public partial class Form1 : Form
{
Bitmap printscreen = new Bitmap(Screen.PrimaryScreen.Bounds.Width, Screen.PrimaryScreen.Bounds.Height);
PictureBox pictureBox1 = new PictureBox();
int zoom = 3; //zoom level
public bool NewZoomLocation = false;
public Form1()
{
{
InitializeComponent();
pictureBox1.Dock = DockStyle.Fill;
pictureBox1.BorderStyle = BorderStyle.FixedSingle;
Controls.Add(pictureBox1);
FormBorderStyle = FormBorderStyle.None;
Timer timer = new Timer();
timer.Interval = 100;
timer.Tick += timer_Tick;
timer.Start();
}
void timer_Tick(object sender, EventArgs e)
{ var position = Cursor.Position;
int xlocation = position.X;
int ylocation = position.Y;
{
try
{
var graphics = Graphics.FromImage(printscreen as Image);
graphics.CopyFromScreen(0, 0, 0, 0, printscreen.Size);
GC.Collect(); // Force the garbage collector (deals with memory leak)
if (NewZoomLocation == true)
{
var lensbmp = new Bitmap(50, 50); //Bitmap for Zoom window
var i = 0;
var j = 0;
for (int row = xlocation - 25; row < xlocation + 25; row++)
{
j = 0;
for (int column = ylocation - 25; column < ylocation + 25; column++)
{
lensbmp.SetPixel(i, j, printscreen.GetPixel(row, column));
j++;
}
i++;
}
this.pictureBox1.Image = new Bitmap(lensbmp, lensbmp.Width * zoom, lensbmp.Height * zoom);
Size = pictureBox1.Image.Size;
Left = xlocation - 45 * (zoom); //Horisontal position of final zoom window
Top = ylocation + 30; //Vertical position of final zoom window
TopMost = true;
}
}
catch //(Exception ex)
{
//MessageBox.Show(ex.Message);
}
}
}
}
protected override void OnKeyDown(KeyEventArgs e)
{
if (e.KeyValue == 73) // I-button to zoom in
zoom++;
else if (e.KeyValue == 79) // O-button to zoom in
zoom--;
else if (e.KeyValue == 27) // Esc-button to exit
{
Close();
Dispose();
}
else if (e.KeyValue == 13) // Enter-button to choose zoon area
{
NewZoomLocation = true;
}
base.OnKeyDown(e);
}
}
}

I'm not really sure what you want to achieve here, however this should get you in a better place.
First thing first. The use of GC.Collect its because you are trying to plug a memory leak, if you ever create an image, dispose of it.
Given some globals
private readonly PictureBox pictureBox1 = new PictureBox();
private Bitmap _lastBmp = new Bitmap(300, 300);
private Point _position;
public bool NewZoomLocation;
private int zoom = 3; //zoom level
Constructor
public Form1()
{
InitializeComponent();
pictureBox1.Dock = DockStyle.Fill;
pictureBox1.BorderStyle = BorderStyle.FixedSingle;
Controls.Add(pictureBox1);
FormBorderStyle = FormBorderStyle.None;
KeyPreview = true;
Size = _lastBmp.Size;
TopMost = true;
var timer = new Timer();
timer.Interval = 100;
timer.Tick += timer_Tick;
timer.Start();
}
Cleanup
protected override void OnClosed(EventArgs e)
{
base.OnClosed(e);
_lastBmp.Dispose();
_lastBmp = null;
}
Keydown
protected override void OnPreviewKeyDown(PreviewKeyDownEventArgs e)
{
base.OnPreviewKeyDown(e);
switch (e.KeyCode)
{
case Keys.Enter:
NewZoomLocation = true;
_position = Cursor.Position;
break;
case Keys.Up:
zoom++;
break;
case Keys.Down:
zoom--;
break;
case Keys.Escape:
Close();
break;
}
}
Timer
private void timer_Tick(object sender, EventArgs e)
{
if (NewZoomLocation)
{
var w = _lastBmp.Size.Width / zoom;
var h = _lastBmp.Size.Height / zoom;
var x = _position.X - w / 2;
var y = _position.Y - h / 2;
var size = new Size(w, h);
using (var screen = new Bitmap(size.Width, size.Height))
{
using (var g = Graphics.FromImage(screen))
{
g.CopyFromScreen(new Point(x, y), Point.Empty, size);
}
// resize
using (var g = Graphics.FromImage(_lastBmp))
{
g.DrawImage(screen, new Rectangle(new Point(), _lastBmp.Size), new Rectangle(0, 0, w, h), GraphicsUnit.Pixel);
}
}
pictureBox1.Image = _lastBmp;
}
}
There is a lot more that can be done with this, however it should get you started. There is no memory leak anymore, it only grabs a screen shot of what it needs so will be faster.
Good luck

Obtain full-page screenshot from WebBrower component

I am attempting to capture a full-page screenshot of any website a user is viewing using the WebBrowser component.
At present, I am able to only able to capture what a user is viewing from within the WebBrowser. However, the screenshot image created is the size of the webpage. For example, below is a (half-sized) screenshot of the BBC website, the black area is actually saved transparent but I've filled it black for visibility.
I have seen solutions where a new WebBrowser instance is used to fetch a fullpage snapshot. However, I need the screenshot to be exactly of the page as the user is viewing it at the time, much like how the full-page screenshot works in Firefox.
My code below that generated the above image:
private void button1_Click(object sender, EventArgs e)
{
while (webBrowser1.ReadyState != WebBrowserReadyState.Complete)
{
Application.DoEvents();
}
int scrollWidth = 0;
int scrollHeight = 0;
scrollHeight = webBrowser1.Document.Body.ScrollRectangle.Height;
scrollWidth = webBrowser1.Document.Body.ScrollRectangle.Width;
webBrowser1.Size = new Size(scrollWidth, scrollHeight);
Bitmap bm = new Bitmap(scrollWidth, scrollHeight);
webBrowser1.DrawToBitmap(bm, new Rectangle(0, 0, bm.Width, bm.Height));
bm.Save(#"D:\Screenshots\test.png", ImageFormat.Png);
}

I've got a good working one..
private void button1_Click(object sender, EventArgs e)
{
using (FileDialog fd = new SaveFileDialog())
{
fd.Filter = "Image (*.png)|*.png";
if (fd.ShowDialog() == System.Windows.Forms.DialogResult.OK)
{
new WebPageSnap(webBrowser1.Url.ToString(), fd.FileName);
//might take 3 or 4 seconds to save cauz it has to load again.
}
}
}
class WebPageSnap
{
WebBrowser wb;
string outFile;
public WebPageSnap(string url, string outputFile)
{
wb = new WebBrowser();
wb.ProgressChanged += wb_ProgressChanged;
outFile = outputFile;
wb.ScriptErrorsSuppressed = true;
wb.ScrollBarsEnabled = false;
wb.Navigate(url);
}
void wb_ProgressChanged(object sender, WebBrowserProgressChangedEventArgs e)
{
if (e.CurrentProgress == e.MaximumProgress)
{
wb.ProgressChanged -= wb_ProgressChanged;
try
{
int scrollWidth = 0;
int scrollHeight = 0;
scrollHeight = wb.Document.Body.ScrollRectangle.Height;
scrollWidth = wb.Document.Body.ScrollRectangle.Width;
wb.Size = new Size(scrollWidth, scrollHeight);
Bitmap bitmap = new Bitmap(wb.Width, wb.Height);
for (int Xcount = 0; Xcount < bitmap.Width; Xcount++)
for (int Ycount = 0; Ycount < bitmap.Height; Ycount++)
bitmap.SetPixel(Xcount, Ycount, Color.Black);
wb.DrawToBitmap(bitmap, new Rectangle(0, 0, wb.Width, wb.Height));
bitmap.Save(outFile, ImageFormat.Png);
}
catch { }
}
}
}
.
;Here's the result
.

Manipulating an image and updating the pictureBox has some issues

I could not fit exactly what I wanted to say in the title, it would be too long. Okay this is a multi-threaded app. What my app does is looks at a picture, find the edges of the picture, and finds the shape of that object from the edges. While it finds the shape, it constantly updates the image so we can get some sort of visual representation. I have created a very short (40 seconds) video demonstrating the issue: http://phstudios.com/projects/Programming/MultiThreadIssue/
As you can see, everything is working fine until the minute I move the window. This is always the case. I ran the program several times without moving the window and it ran fine. However, the minute I move the window, it will come up with that error. As you see, I am locking the specific image I would like to work with. Is the forms OnPaint overriding that somehow? Is there any way I can fix that?
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.Threading;
using System.Drawing.Imaging;
namespace LineRecognition
{
public enum Shape
{
Unknown,
Quadrilateral,
Circle,
Triangle
}
public partial class Form1 : Form
{
Bitmap image, original, shapes;
List<Point> outlines;
Shape shape;
ShapeDetection detector;
public Form1()
{
InitializeComponent();
edgeDetection.WorkerReportsProgress = true;
shapeDetection.WorkerReportsProgress = true;
shape = Shape.Unknown;
}
private void Form1_Load(object sender, EventArgs e)
{
original = new Bitmap("photo1.png");
image = new Bitmap("photo1.png");
shapes = new Bitmap(image.Width, image.Height);
pictureBox1.Image = (Image)original;
}
private void findLines_Click(object sender, EventArgs e)
{
if (edgeDetection.IsBusy != true)
{
lblStatus.Text = "Finding Edges";
edgeDetection.RunWorkerAsync();
}
}
private void justTheOutlines(Bitmap image, List<Point> pixels, BackgroundWorker worker)
{
lock (image)
{
for (int i = 0; i < pixels.Count; i++)
{
image.SetPixel(pixels[i].X, pixels[i].Y, Color.Red);
worker.ReportProgress((int)((float)i * 100 / (float)pixels.Count));
}
}
}
private List<Point> outlineLines(Bitmap image, BackgroundWorker worker)
{
int w = image.Width;
int h = image.Height;
int alpha = 800000;
List<Point> changes = new List<Point>();
lock (image)
{
for (int i = 0; i < w; i++)
{
for (int j = 0; j < h; j++)
{
Color selected = image.GetPixel(i, j);
Color nextRight = selected;
Color nextDown = selected;
if (i < w - 1)
nextRight = image.GetPixel(i + 1, j);
if (j < h - 1)
nextDown = image.GetPixel(i, j + 1);
int iSelected = selected.ToArgb();
int iNextRight = nextRight.ToArgb();
int iNextDown = nextDown.ToArgb();
if (Math.Abs(iSelected - iNextRight) > alpha)
{
if (iSelected < iNextRight)
{
Point p = new Point(i, j);
if(!ContainsPoint(changes, p)) changes.Add(p);
}
else
{
Point p = new Point(i + 1, j);
if (!ContainsPoint(changes, p)) changes.Add(p);
}
}
if (Math.Abs(iSelected - iNextDown) > alpha)
{
if (iSelected < iNextDown)
{
Point p = new Point(i, j);
if (!ContainsPoint(changes, p)) changes.Add(p);
}
else
{
Point p = new Point(i, j + 1);
if (!ContainsPoint(changes, p)) changes.Add(p);
}
}
image.SetPixel(i, j, Color.White);
}
worker.ReportProgress((int)(((float)i / (float)w) * 100));
}
}
return changes;
}
private bool ContainsPoint(List<Point> changes, Point p)
{
foreach (Point n in changes)
{
if (n.Equals(p)) return true;
}
return false;
}
private void edgeDetection_DoWork(object sender, DoWorkEventArgs e)
{
BackgroundWorker worker = sender as BackgroundWorker;
outlines = outlineLines(image, worker);
justTheOutlines(image, outlines, worker);
pictureBox2.Image = (Image)image;
Thread.Sleep(100);
image.Save("photo-lines.jpg");
}
private void edgeDetection_ProgressChanged(object sender, ProgressChangedEventArgs e)
{
algorithmProgress.Value = e.ProgressPercentage;
}
private void edgeDetection_RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e)
{
algorithmProgress.Value = 0;
findLines.Enabled = false;
determineShape.Enabled = true;
lblStatus.Text = "";
}
private void determineShape_Click(object sender, EventArgs e)
{
if (shapeDetection.IsBusy != true)
{
pictureBox1.Image = (Image)image;
lblStatus.Text = "Running Shape Detection: Circle -> Quadrilateral";
shapeDetection.RunWorkerAsync();
}
}
private void ShapeDetection_DoWork(object sender, DoWorkEventArgs e)
{
BackgroundWorker worker = sender as BackgroundWorker;
detector = new ShapeDetection(outlines, 40, 10);
detector.Worker = worker;
detector.circleChange += new ShapeDetection.CircleChangeEventHandler(circleChange);
if (detector.IsCircle())
{
MessageBox.Show("Object is a circle");
shape = Shape.Circle;
}
else if (detector.IsQuadrilateral())
{
MessageBox.Show("Object is a quadrilateral", "Number of edges: " + detector.Summits);
shape = Shape.Quadrilateral;
}
else
{
int sides = detector.Summits.Count;
if (sides == 3)
{
MessageBox.Show("Object is a triangle");
shape = Shape.Triangle;
}
else
{
MessageBox.Show("Number of edges: " + detector.Summits.Count, "Unknown");
}
}
BitmapDrawing.DrawLines(detector.Summits, shapes);
BitmapDrawing.DrawSummits(detector.Summits, shapes);
pictureBox2.Image = (Image)shapes;
Thread.Sleep(100);
}
private void ShapeDetection_RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e)
{
if (detector != null)
{
lblSummits.Text += detector.Summits.Count;
lblType.Text += shape.ToString();
determineShape.Enabled = false;
lblStatus.Text = "";
}
}
void circleChange(object sender, CircleChangeEventArgs e)
{
lock (shapes)
{
Point p = detector.visited[detector.visited.Count - 1];
shapes.SetPixel(p.X, p.Y, Color.Blue);
pictureBox2.Image = (Image)shapes;
Thread.Sleep(10);
detector.Worker.ReportProgress((int)(e.percent * 100));
}
}
private void shapeDetection_ProgressChanged(object sender, ProgressChangedEventArgs e)
{
algorithmProgress.Value = e.ProgressPercentage;
}
}
}
Update
What Nick said before worked fine. I added that to my CircleChange event and it works. Can somebody explain why the invoke makes it work instead of setting the picturebox2.Image to the shapes image? I mean I call it after I call setpixel, so I should be done modifying the image right?
void circleChange(object sender, CircleChangeEventArgs e)
{
Point p = detector.visited[detector.visited.Count - 1];
shapes.SetPixel(p.X, p.Y, Color.Blue);
Image copyForPictureBox = shapes.Clone() as Image;
BeginInvoke(new Action(() => pictureBox2.Image = copyForPictureBox));
Thread.Sleep(15);
detector.Worker.ReportProgress((int)(e.percent * 100));
}

It appears that you're operating on the shapes bitmap on a thread separate to the GUI thread. When you move the window the OnPaint routine will run which will also access the image.
What you need to do to solve this is operate on a separate bitmap in your worker thread, and then pass a copy of that to the GUI thread using Invoke on the form. That way you're guaranteed only to have one thread accessing the picture box image at a time.
Edit:
void MyThreadFunction( )
{
Bitmap localThreadImage;
...
Image copyForPictureBox = localThreadImage.Clone( ) as Image;
BeginInvoke( new Action( () => pictureBox.Image = copyForPictureBox ) );
....
}
So the idea is that you create a Bitmap on the thread which is only ever accessed by that thread (i.e. your background worker thread). And when you get to a point when you want to update the image in the PictureBox you invoke onto the the GUI thread using BeginInvoke (which doesn't block your worker thread) passing a copy of the Bitmap to the PictureBox.

Locking the shapes object at only one point in your application does not accomplish anything. You also use this bitmap to draw to the window, and my guess is that you are not locking it for drawing. You can either lock it in OnPaint as well, or use a different bitmap for manipulation and display.

calling concurrently Graphics.Draw and new Bitmap from memory in thread take long time

Example1
public partial class Form1 : Form
{
public Form1()
{
InitializeComponent();
pro = new Thread(new ThreadStart(Producer));
con = new Thread(new ThreadStart(Consumer));
}
private AutoResetEvent m_DataAvailableEvent = new AutoResetEvent(false);
Queue<Bitmap> queue = new Queue<Bitmap>();
Thread pro;
Thread con;
public void Producer()
{
MemoryStream[] ms = new MemoryStream[3];
for (int y = 0; y < 3; y++)
{
StreamReader reader = new StreamReader("image" + (y + 1) + ".JPG");
BinaryReader breader = new BinaryReader(reader.BaseStream);
byte[] buffer = new byte[reader.BaseStream.Length];
breader.Read(buffer, 0, buffer.Length);
ms[y] = new MemoryStream(buffer);
}
while (true)
{
for (int x = 0; x < 3; x++)
{
Bitmap bmp = new Bitmap(ms[x]);
queue.Enqueue(bmp);
m_DataAvailableEvent.Set();
Thread.Sleep(6);
}
}
}
public void Consumer()
{
Graphics g = pictureBox1.CreateGraphics();
while (true)
{
m_DataAvailableEvent.WaitOne();
Bitmap bmp = queue.Dequeue();
if (bmp != null)
{
// Bitmap bmp = new Bitmap(ms);
g.DrawImage(bmp, new Point(0, 0));
bmp.Dispose();
}
}
}
private void pictureBox1_Click(object sender, EventArgs e)
{
con.Start();
pro.Start();
}
}
When creating bitmap and drawing to picture box are in seperate thread
then Bitmap bmp = new Bitmap(ms[x]) takes 45.591 millisecond
and g.DrawImage(bmp,new Point(0,0)) takes 41.430 milisecond.
When I make a bitmap from memoryStream and draw it to picture box in one thread then
Bitmap bmp = new Bitmap(ms[x]) takes 29.619 and g.DrawImage(bmp,new Point(0,0)) takes 35.540.
The code is for Example 2 is
public Form1()
{
InitializeComponent();
pro = new Thread(new ThreadStart(Producer));
con = new Thread(new ThreadStart(Consumer));
}
private AutoResetEvent m_DataAvailableEvent = new AutoResetEvent(false);
Queue<MemoryStream> queue = new Queue<MemoryStream>();
Thread pro;
Thread con;
public void Producer()
{
MemoryStream[] ms = new MemoryStream[3];
for (int y = 0; y < 3; y++)
{
StreamReader reader = new StreamReader("image" + (y + 1) + ".JPG");
BinaryReader breader = new BinaryReader(reader.BaseStream);
byte[] buffer = new byte[reader.BaseStream.Length];
breader.Read(buffer, 0, buffer.Length);
ms[y] = new MemoryStream(buffer);
}
while (true)
{
for (int x = 0; x < 3; x++)
{
// Bitmap bmp = new Bitmap(ms[x]);
queue.Enqueue(ms[x]);
m_DataAvailableEvent.Set();
Thread.Sleep(6);
}
}
}
public void Consumer()
{
Graphics g = pictureBox1.CreateGraphics();
while (true)
{
m_DataAvailableEvent.WaitOne();
//Bitmap bmp = queue.Dequeue();
MemoryStream ms = queue.Dequeue();
if (ms != null)
{
Bitmap bmp = new Bitmap(ms);
g.DrawImage(bmp, new Point(0, 0));
bmp.Dispose();
}
}
}
private void pictureBox1_Click(object sender, EventArgs e)
{
con.Start();
pro.Start();
}
Why does it take more time to draw and create a bitmap in seperate thread and how to reduce the time when processing in seperate thread ? I am using ANTS performance profiler 4.3

All UI operations should take place on the same thread. In fact if you want your system to be stable they must all take place on the same thread. I guess that what you're seeing with the slower performance on the multithreaded code is evidence of that instability.
By all means load the images in separate threads, but update the UI in the main thread.
If you search for questions tagged [multithreading] [c#] here on Stack Overflow you'll see many other questions along the same lines as yours.
See here and here for example.