Question

I have a function which isn’t so complicated, but for some reason, each time I call it, it freezes the screen for like quarter of a second. This function is on a timer and is deployed every second so it can get pretty annoying to the user.

The function basically gets a screen shot of the screen, checks if the screen that it’s looking for by comparing 10 pixels and returns true if that’s the screen or false otherwise :

ClassName.CheckScreen(CaptureScreen(),ClassName.Pxarr1); //Capture screen isn't the problem. It gave me no freezes in an endless loop.

Thats the class :

class ClassName
{
    public static Pixel[] Pxarr1 = new[]
    {
        new Pixel(Color.FromArgb(255, 204, 204, 170), new Point(15, 145)),
        new Pixel(Color.FromArgb(255, 221, 204, 187), new Point(20, 460)),
        new Pixel(Color.FromArgb(255, 221, 204, 187), new Point(20, 545)),
        new Pixel(Color.FromArgb(255, 204, 187, 170), new Point(15, 150)),
        new Pixel(Color.FromArgb(255, 221, 204, 187), new Point(22, 190)),
        new Pixel(Color.FromArgb(255, 204, 204, 187), new Point(25, 540)),
        new Pixel(Color.FromArgb(255, 204, 187, 153), new Point(22, 61)),
        new Pixel(Color.FromArgb(255, 221, 204, 170), new Point(23, 563)),
        new Pixel(Color.FromArgb(255, 204, 187, 153), new Point(23, 47)),
        new Pixel(Color.FromArgb(255, 204, 204, 187), new Point(23, 463)),

    };

    public static Pixel[] Pxarr2 = new[]
    {
        new Pixel(Color.FromArgb(255, 221, 255, 119), new Point(80, 120)),
        new Pixel(Color.FromArgb(255, 51, 119, 221), new Point(180, 525)),
        new Pixel(Color.FromArgb(255, 204, 170, 85), new Point(630, 455)),
        new Pixel(Color.FromArgb(255, 85, 153, 17), new Point(707, 177)),
        new Pixel(Color.FromArgb(255, 255, 153, 34), new Point(520, 440)),
        new Pixel(Color.FromArgb(255, 255, 238, 51), new Point(150, 325)),
        new Pixel(Color.FromArgb(255, 0, 85, 255), new Point(455, 70)),
        new Pixel(Color.FromArgb(255, 255, 221, 51), new Point(685, 285)),
        new Pixel(Color.FromArgb(255, 17, 17, 17), new Point(547, 369)),
        new Pixel(Color.FromArgb(255, 170, 170, 136), new Point(500, 545)),

    };

    public static Pixel[] Pxarr3 = new[]
    {
        new Pixel(Color.FromArgb(255, 238, 238, 238), new Point(353, 223)),
        new Pixel(Color.FromArgb(255, 28, 33, 49), new Point(428, 198)),
        new Pixel(Color.FromArgb(255, 85, 85, 85), new Point(462, 314)),
        new Pixel(Color.FromArgb(255, 221, 221, 238), new Point(450, 450)),
        new Pixel(Color.FromArgb(255, 102, 102, 102), new Point(384, 349)),
        new Pixel(Color.FromArgb(255, 204, 204, 204), new Point(406, 248)),
        new Pixel(Color.FromArgb(255, 221, 221, 221), new Point(464, 453)),
        new Pixel(Color.FromArgb(255, 255, 204, 17), new Point(413, 198)),
        new Pixel(Color.FromArgb(255, 204, 204, 204), new Point(343, 447)),
        new Pixel(Color.FromArgb(255, 255, 255, 255), new Point(403, 457)),

    };

    public static Pixel[] Pxarr4 = new[]
    {
        new Pixel(Color.FromArgb(255, 204, 170, 136), new Point(120, 227)),
        new Pixel(Color.FromArgb(255, 221, 187, 153), new Point(502, 170)),
        new Pixel(Color.FromArgb(255, 119, 85, 34), new Point(692, 243)),
        new Pixel(Color.FromArgb(255, 238, 221, 187), new Point(211, 169)),
        new Pixel(Color.FromArgb(255, 187, 170, 136), new Point(272, 238)),
        new Pixel(Color.FromArgb(255, 170, 153, 119), new Point(696, 64)),
        new Pixel(Color.FromArgb(255, 136, 85, 17), new Point(306, 242)),
        new Pixel(Color.FromArgb(255, 187, 170, 119), new Point(115, 236)),
        new Pixel(Color.FromArgb(255, 204, 187, 153), new Point(310, 183)),
        new Pixel(Color.FromArgb(255, 153, 102, 34), new Point(647, 245)),

    };

    public static Pixel[] Pxarr5 = new[]
    {
        new Pixel(Color.FromArgb(255, 255, 238, 221), new Point(376, 150)),
        new Pixel(Color.FromArgb(255, 255, 238, 221), new Point(376, 350)),

        new Pixel(Color.FromArgb(255, 255, 238, 221), new Point(506, 150)),
        new Pixel(Color.FromArgb(255, 255, 238, 221), new Point(506, 350)),

        new Pixel(Color.FromArgb(255, 255, 238, 221), new Point(246, 150)),
        new Pixel(Color.FromArgb(255, 255, 238, 221), new Point(246, 350))
    };

    public static bool CheckScreen(Bitmap img, Pixel[] samples)
    {
        int verifiedpixels = 0;
        for (int i = 0; i < samples.Length; i++)
        {
            Color c = img.GetPixel(samples[i].Location.X, samples[i].Location.Y);
            if (c == samples[i].Color)
                    verifiedpixels++;
        }
        return verifiedpixels >= (samples.Length * 0.6);
    }

}

Note : A 100 loop for statement was twice as slow with CaptureScreen() than with an image from a file.
(4 seconds vs 2 seconds)

But still, I don’t understand why this function casuses any freezing, even with an image from a file.

Answer 1

Since you are using a timer, it should not freeze the UI, unless you are using System.Windows.Forms.Timer which will execute its call back on the UI thread. Instead use System.Timers.Timer or System.Threading.Timer.
Example for System.Timers.Timer:

private System.Timers.Timer _checkPixelsTimer = new System.Timers.Timer();

public Form1()
{
    InitializeComponents();

    _checkPixelsTimer.Intervla = 1000;//one second
    _checkPixelsTimer.AutoReset = true;
    _checkPixelsTimer.Elapced += OnCheckPixelsTimerElapced;
    _checkPixelsTimer.Start();
}

private void OnCheckPixelsTimerElapced(object sender, System.Timer.ElapcedEventArgs e)
{
    if (ClassName.CheckScreen(CaptureScreen(),ClassName.Pxarr1))
    {
        MethodInvoker method = new MethodInvoker(() => { /*code that relays on the UI thread */ });
        if (this.InvokeRequired)
        {
            this.Invoke(method); 
        }
        else
        {
            method();
        }
    }
}

Edit: update the code to preview how to call a function at the UI thread.