how to draw drawings in picture box

问题

draw pictures in picture Box on Mouse dragging using c#

回答1:

Put a PictureBox on your form, and set its BackColor to White. Then add this code to your form (you have to actually hook up the Mouse events below, i.e. you can't just copy and paste this code into your form):

private Point? _Previous = null;
private void pictureBox1_MouseDown(object sender, MouseEventArgs e)
{
    _Previous = e.Location;
    pictureBox1_MouseMove(sender, e);
}
private void pictureBox1_MouseMove(object sender, MouseEventArgs e)
{
    if (_Previous != null)
    {
        if (pictureBox1.Image == null)
        {
            Bitmap bmp = new Bitmap(pictureBox1.Width, pictureBox1.Height);
            using (Graphics g = Graphics.FromImage(bmp))
            {
                g.Clear(Color.White);
            }
            pictureBox1.Image = bmp;
        }
        using (Graphics g = Graphics.FromImage(pictureBox1.Image))
        {
            g.DrawLine(Pens.Black, _Previous.Value, e.Location);
        }
        pictureBox1.Invalidate();
        _Previous = e.Location;
    }
}
private void pictureBox1_MouseUp(object sender, MouseEventArgs e)
{
    _Previous = null;
}

And then draw away!

If you like, you can improve the quality of the drawn image somewhat by setting the Graphics object's SmoothingMode property.

Update: .Net CF does't have the Pens collection, and MoustEventArgs doesn't have a Location, so here is a CF-friendly version:

private Point? _Previous = null;
private Pen _Pen = new Pen(Color.Black);
private void pictureBox1_MouseDown(object sender, MouseEventArgs e)
{
    _Previous = new Point(e.X, e.Y);
    pictureBox1_MouseMove(sender, e);
}
private void pictureBox1_MouseMove(object sender, MouseEventArgs e)
{
    if (_Previous != null)
    {
        if (pictureBox1.Image == null)
        {
            Bitmap bmp = new Bitmap(pictureBox1.Width, pictureBox1.Height);
            using (Graphics g = Graphics.FromImage(bmp))
            {
                g.Clear(Color.White);
            }
            pictureBox1.Image = bmp;
        }
        using (Graphics g = Graphics.FromImage(pictureBox1.Image))
        {
            g.DrawLine(_Pen, _Previous.Value.X, _Previous.Value.Y, e.X, e.Y);
        }
        pictureBox1.Invalidate();
        _Previous = new Point(e.X, e.Y);
    }
}
private void pictureBox1_MouseUp(object sender, MouseEventArgs e)
{
    _Previous = null;
}

回答2:

Here, pictureBox1 == signature. I translated to vb in this manner:

Global:

Dim _previous As Point = Nothing
Dim _pen As Pen = New Pen(Color.Black)
Dim drawing As Boolean = False


''' <summary>
''' This handles the signature drawing events (drawing)
''' </summary>
''' <param name="sender"></param>
''' <param name="e"></param>
''' <remarks></remarks>
Private Sub signature_MouseMove(ByVal sender As System.Object, ByVal e As System.Windows.Forms.MouseEventArgs) Handles signature.MouseMove
    If drawing = True Then
        If signature.Image Is Nothing Then
            Dim bmp As Bitmap = New Bitmap(signature.Width, signature.Height)

            Using g As Graphics = Graphics.FromImage(bmp)
                g.Clear(Color.White)
            End Using

            signature.Image = bmp
        End If

        Using g As Graphics = Graphics.FromImage(signature.Image)
            g.DrawLine(_pen, _previous.X, _previous.Y, e.X, e.Y)
        End Using
        signature.Invalidate()
        _previous = New Point(e.X, e.Y)
    End If
End Sub

''' <summary>
''' this indicates somebody is going to write a signature
''' </summary>
''' <param name="sender"></param>
''' <param name="e"></param>
''' <remarks></remarks>
Private Sub signature_MouseDown(ByVal sender As System.Object, ByVal e As System.Windows.Forms.MouseEventArgs) Handles signature.MouseDown
    _previous = New Point(e.X, e.Y)
    drawing = True
    signature_MouseMove(sender, e)

End Sub

''' <summary>
''' the signature is done.
''' </summary>
''' <param name="sender"></param>
''' <param name="e"></param>
''' <remarks></remarks>
Private Sub signature_MouseUp(ByVal sender As System.Object, ByVal e As System.Windows.Forms.MouseEventArgs) Handles signature.MouseUp
    _previous = Nothing
    drawing = False
End Sub

回答3:

You can do it by capturing the mousemove event of picture box then get graphics from picture box like .

Graphics g= pictureBox.CreateGraphics(); then u can draw whatever u want draw using this graphics object

来源：https://stackoverflow.com/questions/1537090/how-to-draw-drawings-in-picture-box

标签

picturebox