Transparent user control

Question

hi,

i need to create a transparent user control in which we can set the OPACITY of that control as we do in forms.

im using c# 2005.

thanks in advance for ur help..!

 

Answer 1

To make a UserControl transparent, we have to give it a WS_EX_TRANSPARENT style, override its OnPaintBackground method to draw the background with the opacity, and then invalidates its Parent to redraw the control whenever we need to update the graphics, I write the following sample for your information:

Code Block

public partial class UserControl1 : UserControl

    {

        public UserControl1()

        {

            InitializeComponent();

        }

 

        protected override CreateParams CreateParams

        {

            get

            {

                CreateParams cp = base.CreateParams;

                cp.ExStyle |= 0x00000020;//WS_EX_TRANSPARENT

                return cp;

            }

        }

 

        private int opacity;

 

        public int Opacity

        {

            get { return opacity; }

            set {

                opacity = value;

                this.InvalidateEx();

            }

        }

 

        protected override void OnPaintBackground(PaintEventArgs e)

        {

            Color bk = Color.FromArgb(Opacity, this.BackColor);

            e.Graphics.FillRectangle(new SolidBrush(bk), e.ClipRectangle);

        }

 

        protected void InvalidateEx()

        {

            if (Parent == null)

                return;

            Rectangle rc = new Rectangle(this.Location, this.Size);

            Parent.Invalidate(rc, true);

        }

    }

 

 

And codes for testing:

Code Block

public partial class Form5 : Form

    {

        public Form5()

        {

            InitializeComponent();

        }

 

        private void Form5_Load(object sender, EventArgs e)

        {

            this.BackgroundImage = Image.FromFile(@"c:\images\test.jpg");

            this.trackBar1.Minimum = 0;

            this.trackBar1.Maximum = 100;

            this.trackBar1.ValueChanged += new EventHandler(trackBar1_ValueChanged);

        }

 

        void trackBar1_ValueChanged(object sender, EventArgs e)

        {

            int opacity = (int)((this.trackBar1.Value * 255) / 100);

            this.userControl11.Opacity = opacity;

        }

    }

 

 

Answer 2

Unfortunately the controls on the UserControl surface are not transparent-ified when I try this technique.

Would I need to perform a similar operation on those controls as well? Would that even work?

Currently I've only got an image and a label on the UserControl in question, so if you have any suggestions I'd appreciate it.

Thanks!


[edit]

After thinking about this a bit... (think, think, think...) would it be possible to just draw the image and the text on the UserControl surface, and if so, would those become transparent automatically?

Just trying to think of a relatively simple workaround...

[/edit]

Answer 3

Thank you I have been look for this solution for very long time.

Answer 4

Hello, first of all thank you for the tip !

 

In order to have every contained control with cleaner background, please modify the OnPaintBackground function like that :

    protected override void OnPaintBackground(PaintEventArgs e)
    {
      Color l_colBackground = Color.FromArgb(Opacity, this.BackColor);
      e.Graphics.FillRectangle(new SolidBrush(l_colBackground), e.ClipRectangle);

      Brush l_brFilled = new SolidBrush(Color.FromArgb(255, this.BackColor));

      foreach(Control l_ctrlCurrent in this.Controls)
        if(l_ctrlCurrent.Visible) 
          e.Graphics.FillRectangle(l_brFilled, l_ctrlCurrent.Bounds);
    }

Answer 5

private int opacity = 100;
public Color brushColor = Color.DeepSkyBlue;//any color you want


        protected override CreateParams CreateParams
        {
            get
            {
                CreateParams cp = base.CreateParams;
                cp.ExStyle |= 0x20;
                return cp;
            }
        }

        protected override void OnPaintBackground(PaintEventArgs e)
        {
             
        }

        protected override void OnMove(EventArgs e)
        {
            base.RecreateHandle();
           
        }

        public Color BrushColor
        {
            get
            {
                return this.brushColor;
            }
            set
            {
                this.brushColor = value;
                base.RecreateHandle();
            }
        }

        public int Opacity
        {
            get
            {
                if (this.opacity > 100)
                {
                    this.opacity = 100;
                }
                else if (this.opacity < 0)
                {
                    this.opacity = 0;
                }
                return this.opacity;
            }
            set
            {
                this.opacity = value;
                base.RecreateHandle();
            }
        }


        protected override void OnPaint(PaintEventArgs e)
        {
            int num;
            Graphics graphics = e.Graphics;
            Rectangle rect = new Rectangle(-1, -1, base.Width + 1, base.Height + 1);
            Color brushColor = this.brushColor;
            if (brushColor == Color.Transparent)
            {
                num = 0;
            }
            else
            {
                num = (this.opacity * 0xff) / 100;
            }
            Pen pen = new Pen(Color.FromArgb(num, brushColor));
            SolidBrush brush = new SolidBrush(Color.FromArgb(num, brushColor));
            
            //Draw Rectangle
            graphics.FillRectangle(brush, rect);  
            graphics.DrawRectangle(pen, rect);

            //Draw Ellipse
            //graphics.FillEllipse(brush, rect);
            //graphics.DrawEllipse(pen, rect);
            pen.Dispose();
            brush.Dispose();
            graphics.Dispose();
        }