Timed resize of image - C# Discussion Boards

The keys are stored in the certificate, which is in the windows certificate store. This means that they are separated from the process. However, in order to get access to the crtificate, a password is required. We are not trying to deny the users access to this certificate, but since the relevant process is running as an unattended process, there is no user to ask for the password. We therefore store this password in a separate file, but we want to avoid a readable password to be around somewhere on the system, so we encrypt this password, using an algorithm that does not require any further keys. However, we want to keep the decryption process as secret as we can, which is why the reverse-engineering possibility of c# is a bother.

Can you not just export the certificate's public key without a password? I thought only the private key needed the password?

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Just to throw this out there. You should look up the concept of "Security through Obscurity" and why its a bad idea. To put it simply...the problem with maintaining security through obscurity means your mechanism of security hasn't really been tested. Even if you use obfuscation techniques to maintain your obscurity, eventually someone is going to figure out how to get around it and that someone will put your security algorithms to the test. Given the nature of digital security and based on the wealth of knowledge provided by cryptoanalysts, using a mainstream, thouroughly tested security algorithm is more likely to give you better security than a home-grown solution that has never really, truely been tested. Good mainstream algorithms that have been vetted by the crytoanalyst community have been put through rigorous testing over many years, and are generally prooven to be secure against attack.

Just my two cents anyway.

Hi,

I'm using Application.Idle to do some background processing. The background processing updates a progress bar making it easy to tell if it's running or not.

I notice that if I launch a SaveFileDialog(), the background process is suspended which is exactly what I want to happen. However when I create my own modal dialog, the background process continues to when the ShowDialog() method is called.

Any ideas on why there's a difference between the two? Shouldn't all modal dialogs behave the same when it comes to event processing?

Thanks.
-- Greg

Hello,

I've noticed that when I'm running code, everything becomes devoted to running that program.

Most code I write doesn't need to do stuff all the time, just once in awhile it should do a particular operation and then become idle.

What's a quick way for me to make sure my programs aren't hogging up resources?

Thanks in advance,
Michael Fritzius

I would use an application like CLR Profiler if I were you. Check this to see where code is inefficient.

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Hi,

it sounds like you have one or more empty loops, i.e. a loop testing some condition and when (not) met
just start the next iteration. Each of those is a good recipe for keeping one core busy. The easy way
out is to include a Thread.Sleep(100) in all such loops. The clean approach is to make things entirely
event-driven so you don't need polling loops at all.

Smile | :)

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modified on Friday, June 10, 2011 11:25 PM

Hi,
I'm trying to make the images in a super slide show to automatically enlarge. Super because I want to control the images with a timer accuracy of 1 millisecond.
So I've got a timer event set up. That changes the image (according to a config file) every x ms.
When the image is shown I want the image to grow larger (including beyond the size of the screen) to create the effect of flying into the image.

I can't get it to work.

Here's the code:

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.IO;
using Multimedia; //For the MM timer
using System.Windows.Forms;

namespace MyImage
{
public partial class Form1 : Form
{
public delegate void ScaleImageDelegate(); //public delegate void WriteDataDelegate(object sender, EventArgs eArgs);
Multimedia.Timer myTimer = new Multimedia.Timer(); //Define a new 1ms resolution timer
int TimeCounter, ImageCounter;
bool DoScale = false;
Bitmap[] myImage = new Bitmap[10];
string[] ImageName = new string[10];
int[] ImageStart = new int[10];
int[] ImageDuration = new int[10];
int TotalNumberofImages;
float Scaler = 1;

public Form1()
{
InitializeComponent();
myTimer.Mode = TimerMode.Periodic; //Make sure the timer keeps running after the set period
myTimer.Period = 10; //Set the period (when the Event is triggered) to x ms
myTimer.Resolution = 1; //Set the resolution of the timer to 1ms
this.myTimer.Tick += new System.EventHandler(this.myTimer_Tick); //Initialize the EventHandler
GetFiles(); //REad the images in an array for fast display
myTimer.Start(); //Start the timer and thus the Event Handler and do something
TimeCounter = 0; //Reset the timer counter
ImageCounter = 0;
}

void myTimer_Tick(object sender, System.EventArgs args)
{
TimeCounter += 1; //an other 10ms has elapsed
if (TimeCounter * 10 == ImageStart[ImageCounter])
{
pictureBox1.Image = myImage[ImageCounter];
ScaleImage();
}
if (TimeCounter * 10 == ImageStart[ImageCounter] + ImageDuration[ImageCounter])
{
pictureBox1.Image = myImage[4];
ImageCounter += 1;
DoScale = false;
if (ImageCounter > TotalNumberofImages)
{
Application.Exit();
}
}
if (DoScale)
{
ScaleImage();
}
}

void GetFiles()
{
TextReader tr = new StreamReader(@"c:\data\images.dat");
char[] seps = { ';' };
String line;
String[] values;
int i =0;

while ((line = tr.ReadLine()) != null)
{
values = line.Split(seps);
ImageName[i] = values[0];
ImageStart[i] = int.Parse(values[1]);
ImageDuration[i] = int.Parse(values[2]);
i++;
}
TotalNumberofImages = i - 1;

for (i = 0; i <= TotalNumberofImages; i++)
{
myImage[i] = new Bitmap(ImageName[i]);
}
// close the stream
tr.Close();
}

private void ScaleImage()
{
double myWidth, myHeight;
if (InvokeRequired)
{
BeginInvoke(new ScaleImageDelegate(ScaleImage));
return;
}
if (!DoScale)
{
Scaler = 1;
DoScale = true;
}
Scaler += 0.01f;
myWidth = Convert.ToDouble(pictureBox1.Width) * Convert.ToInt32(Scaler);
pictureBox1.Width = Convert.ToInt32(myWidth);
myHeight = Convert.ToDouble(pictureBox1.Height) * Convert.ToInt32(Scaler);
pictureBox1.Height = Convert.ToInt32(myHeight);
}
}
}

THX!
Marco

I for one cannot be bothered to read all that.

Does your have an error message to go with it?
Or perhaps you could say what it is that doesnt work how you want

My opinion is... If someone has already posted an answer, dont post the SAME answer

There is no error. It just does not work.
This is the run down:

1) Show an image full screen every 1 second using a timed event
2) When the image is on screen, enlarge gradually it during that 1 second to 200% (so overflowing the screen). So at 1.5s the image should be at 150%, etc.

What it does do is quit after the first image.
As far as I can see it has something to do with the threading as it finishes the program (stop in the program.cs at the call to Form1) when it checks if (BeginInvoke)...

modified on Friday, February 6, 2009 9:02 AM

oh, i understood what you want, it just seems you want others to do all the work. you may have posted code but you have no clue as to what is failing.

Im not familiar with the Multimedia.Timer - why not you System.Windows.Forms.Timer?
Also a think you may need to take into account the delay in loading an image every second

maybe you should try loading an image, then starting the timer (set at 10ms or something) then with every tick then you update the size of a bitmap.

Why dont you try using a panel and handle the paint event yourself to do the bitmap drawing, rather than using a picturebox

My opinion is... If someone has already posted an answer, dont post the SAME answer

Errr, isn't helping THE idea behind message boards?
The Forms.Timer is not accurate enough. It runs for several ms then hickups about 16ms. The MM timer is the only one I've found that will do the trick.
I avoid the load delay by pre-loading the images in an array.

I have tried timer, image, resize. Didn't work, at least not the way I did it.

Thanks for the Paint event suggestion, I will take another look at it.

Yes and i like to help, but i dont have the time to evalute all of your code when you dont give specific issues.

m.otte wrote:
I avoid the load delay by pre-loading the images in an array.

I beleive you may also get a delay while assigning a picturebox with an image, only small i know, but as your doing a very time-tight operation you want to avoid as much assignment in loops as posible

P.S. thanks for the info on the timer

My opinion is... If someone has already posted an answer, dont post the SAME answer

m.otte wrote:
What it does do is quit after the first image.
As far as I can see it has something to do with the threading as it finishes the program (stop in the program.cs at the call to Form1) when it checks if (BeginInvoke)...

check the imageCounter is not greater than numOfImages (or what ever check it was that causes application.Exit();

if your thread is failing you wont get debug errors, you need to put debug messages in yourself to test.

Try running it on same thread and see if any error messages

My opinion is... If someone has already posted an answer, dont post the SAME answer

It doesn't reach the app.exit! I checked.
Trying to run it in the same thread causes the Cross Thread error to pop up as soon as the execution reaches the size update of the picturebox.

how can you get a crossthread error if you only using one thread?

My opinion is... If someone has already posted an answer, dont post the SAME answer

As far as I understand, the Timer has a thread and the Form has.
I might be wrong, but then I don't know where the other thread comes from.

As i said i only new the Forms.Timer which the tick event does not cause another thread.

If your timer is having another thread, then you may be getting a cross-thread error you dont know about while using the other thread in your application (as said, errors will not show in thread other than main) does that make sense?

My opinion is... If someone has already posted an answer, dont post the SAME answer

This is the MM timer: http://www.codeproject.com/KB/miscctrl/lescsmultimediatimer.aspx[^]

Yep ,you make perfect sense. I'll first try the Paint Event again. Tried is before but couldn't get it to work the way I wanted (inside a timer event).

with a paintEvent method, the timer should set a global scale value, and then call the panel.Invalidate() method

the paint event should, draw the required image using the global scale value and other positioning calculations

My opinion is... If someone has already posted an answer, dont post the SAME answer

Mmm, I see. Interesting. Will try it and am curious what it will do to the timing?

Thanks

Right. If you want specific actions with images, don't rely on PictureBoxes; use some drawing surface and paint the stuff yourself. Panels are ideal for such purposes.

Smile | :)

Luc Pattyn [Forum Guidelines] [My Articles]

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- the quality and detail of your question reflects on the effectiveness of the help you are likely to get
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modified on Friday, February 6, 2009 12:57 PM

modified on Friday, June 10, 2011 11:30 AM

Thanks for the backup Big Grin | :-D

My opinion is... If someone has already posted an answer, dont post the SAME answer

Hi,

almost all asynchronous devices including serial ports, timers, etc. use extra threads. All timers except one (Forms.Timer) tick on a separate thread, and are not suited for directly touching any Control. One either needs Control.InvokeRequired + Control.Invoke, or use Forms.Timer

Smile | :)

Luc Pattyn [Forum Guidelines] [My Articles]

- before you ask a question here, search CodeProject, then Google
- the quality and detail of your question reflects on the effectiveness of the help you are likely to get
- use the code block button (PRE tags) to preserve formatting when showing multi-line code snippets

modified on Friday, June 10, 2011 11:31 AM

Hey everybody... I got a question for advanced C# programmers. I've been playing around with type constraints for template classes, and I got stuck.
I used [ and ] instead of < and > for template classes because I wanted to have HTML code for you to see better what code I got.

In the C# 3.0 specification (and I will quote directly from Microsoft's document), it's said that this will work:

class B[T] where T: IEnumerable {...}
class D[T]: B[T] where T: IEnumerable {...}
class E[T]: B[List[T]] {...}

Because (so they say):

"Since type parameters are not inherited, constraints are never inherited either. In the example below, D needs to specify the constraint on its type parameter T so that T satisfies the constraint imposed by the base class B[T]. In contrast, class E need not specify a constraint, because List[T] implements IEnumerable for any T."

Now... I put this pre into VS 2008 and the compiler won't work. My pre:

class B[T] where T : IEnumerable[T] { }
class D[T] : B[T] where T : IEnumerable[T] { }
class E[T] : B[List[T]] { }

Error:

"Error 1 The type 'System.Collections.Generic.List[T]' cannot be used as type parameter 'T' in the generic type or method 'FunFollAdmin.frmMain.B[T]'. There is no implicit reference conversion from 'System.Collections.Generic.List[T]' to 'System.Collections.Generic.IEnumerable[System.Collections.Generic.List[T]]'. D:\Order\A1.FunFoll Administrator [FFA]\2009-01-25\FunFollAdmin\frmMain.cs 46 10 FunFollAdmin"

Even more......... not even this works:

B[test] test = new B[test]();

Error:

"Error 1 The type 'FunFollAdmin.frmMain.test' cannot be used as type parameter 'T' in the generic type or method 'FunFollAdmin.frmMain.B[T]'. There is no implicit reference conversion from 'FunFollAdmin.frmMain.test' to 'System.Collections.Generic.IEnumerable[FunFollAdmin.frmMain.test]'. D:\Order\A1.FunFoll Administrator [FFA]\2009-01-25\FunFollAdmin\frmMain.cs 216 9 FunFollAdmin
Error 2 The type 'FunFollAdmin.frmMain.test' cannot be used as type parameter 'T' in the generic type or method 'FunFollAdmin.frmMain.B[T]'. There is no implicit reference conversion from 'FunFollAdmin.frmMain.test' to 'System.Collections.Generic.IEnumerable[FunFollAdmin.frmMain.test]'. D:\Order\A1.FunFoll Administrator [FFA]\2009-01-25\FunFollAdmin\frmMain.cs 216 28 FunFollAdmin"

Even though I have implemented the class test correctly:

class test : IEnumerable[int]
{
  public test () { }
  #region IEnumerable[int] Members

  public IEnumerator[int] GetEnumerator ()
  {
    throw new NotImplementedException();
  }

  #endregion

  #region IEnumerable Members

  System.Collections.IEnumerator System.Collections.IEnumerable.GetEnumerator ()
  {
    throw new NotImplementedException();
  }

  #endregion
}

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