c# chart vertical text annotation

Question

I'm adding annotations to a c# line chart. I'd like to change the text orientation but can't see any setting to allow this.

RectangleAnnotation annotation = new RectangleAnnotation();
annotation.AnchorDataPoint = chart1.Series[0].Points[x];
annotation.Text = "look an annotation";
annotation.ForeColor = Color.Black;
annotation.Font = new Font("Arial", 12); 
annotation.LineWidth = 2;   
chart1.Annotations.Add(annotation);

The annotation is added to the graph correctly and the rectangle and text run left to right. I want to orientate it to run up and down. Any suggestions on how to achieve this?

I am curious if you ever found a solution to this problem or if you ever got it to work. — tmwoods, Mar 06 '13 at 16:02

score 1 · Answer 1 · answered Mar 29 '22 at 11:33

The solution that worked for me.

First, add the annotation as usual. The key is to make it invisible and then draw it manually in the Chart.PostPaint event.

var text = new RectangleAnnotation();
text.ClipToChartArea = chart.ChartAreas[0].Name;
text.Text = "Title";
text.AxisX = chart.AxisX;
text.AxisY = chart.AxisY;
text.X = value;
text.Y = chart.AxisY.Maximum;
text.BackColor = chart.BaseSettings.ColorStorage["First"][1]; // Use your colors
text.LineColor = chart.BaseSettings.ColorStorage["First"][1];
text.ForeColor = Color.White;
text.Visible = false; // <- Hide the annotation.
chart.graph.Annotations.Add(text);
text.ResizeToContent();

Secondly, manually draw the text in Chart.PostPaint.

private static void ChartPostPaint(object sender, ChartPaintEventArgs e)
{    
    var chart = (Chart)sender;

    foreach (var annotation in chart.Annotations)
    {
        var text = annotation as RectangleAnnotation;
        if (text == null || text.Visible)
        {
            /* Skip all other irrelevant annotations and those which are visible. */
            continue;
        }

        var g = e.ChartGraphics.Graphics;
        var m = g.MeasureString(text.Text, text.Font);

        /* Convert the chart coordinates to the absolute values. */
        float x = (float)e.ChartGraphics.GetPositionFromAxis(text.ClipToChartArea, AxisName.X, text.X);
        float y = (float)e.ChartGraphics.GetPositionFromAxis(text.ClipToChartArea, AxisName.Y, text.Y);
        float w = m.Height;
        float h = m.Width;

        var p = e.ChartGraphics.GetAbsolutePoint(new PointF(x, y));

        using (var bg = new SolidBrush(text.BackColor))
        using (var fc = new SolidBrush(text.ForeColor))
        {
            g.FillRectangle(bg, p.X - m.Height, p.Y, w, h);

            /* Rotate the surface by 270 degrees around the text. */
            var dx = p.X - (m.Height / 2f);
            var dy = p.Y + (m.Height / 2f);
            g.TranslateTransform(dx, dy);
            g.RotateTransform(270);
            g.TranslateTransform(-dx, -dy);

            /* Draw the text as usual */
            g.DrawString(text.Text, text.Font, fc, p.X - m.Width, p.Y + 1);
            
            /* And rotate it back. */
            g.ResetTransform();
        }
    }
}

score 0 · Answer 2 · edited May 23 '17 at 11:45

You cannot rotate annotations using the annotation library. You have to use postpaint or prepaint. Here is a good example of how to use the post-paint event. Hope this helps. I'll include the code from the link below:

protected void Chart1_PostPaint(object sender, ChartPaintEventArgs e)
{
if (e.ChartElement is Chart)
{
    // create text to draw
    String TextToDraw;
    TextToDraw = "Printed: " + DateTime.Now.ToString("MMM d, yyyy @ h:mm tt");
    TextToDraw += " -- Copyright © Steve Wellens";

    // get graphics tools
    Graphics g = e.ChartGraphics.Graphics;
    Font DrawFont = System.Drawing.SystemFonts.CaptionFont;
    Brush DrawBrush = Brushes.Black;

    // see how big the text will be
    int TxtWidth = (int)g.MeasureString(TextToDraw, DrawFont).Width;
    int TxtHeight = (int)g.MeasureString(TextToDraw, DrawFont).Height;

    // where to draw
    int x = 5;  // a few pixels from the left border

    int y = (int)e.Chart.Height.Value;
    y = y - TxtHeight - 5; // a few pixels off the bottom

    // draw the string        
    g.DrawString(TextToDraw, DrawFont, DrawBrush, x, y);
}

}

EDIT: I just realized this example doesn't actually rotate the text. I know you have to use this tool so I will try to find an example using postpaint that rotates text.

EDIT 2: Aaah. Right here at SO. Basically you need to use the e.Graphics.RotateTransform(270); property (that line would rotate 270 degrees).

Unfortunately it seems to be impossible unless you actually do it in the Paint event itself! The e.ChartGraphics.Graphics doesn't work with rotations — TaW, Sep 20 '16 at 21:10

c# chart vertical text annotation

2 Answers2

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