How to draw a string at an exact pixel position

问题

I try to draw a string (single character) in C# into a Bitmap at an exact position with:

Bitmap bmp = new Bitmap(64, 64);
Graphics g = Graphics.FromImage(bmp);
g.DrawString("W", font1, new SolidBrush(myColor), new Point(32,32);

There is so much empty space rendered around a single letter, that I can not guess the "needed" position to draw the character to have it at the correct position at the end.

By now I have the pixel exact dimension of the character (looking at bits in a separately rendered bitmap). But this information is useless, if I cannot draw the character at an exact position (e.g. center or top right corner or ....).

Are there other methods to draw text in C# on a bitmap? Or are there any converting methods to convert the real pixel position in something DrawString needs?

回答1:

No need to look at the pixels or start working with your own font..

You can use a GraphicsPath instead of DrawString or TextRenderer, as it will let you know its net bounds rectangle with GraphicsPath.GetBounds() .

When you know it, you can calculate how to move the Graphics object using TranslateTransform:

private void button1_Click(object sender, EventArgs e)
{
    string text = "Y";                  // whatever
    Bitmap bmp = new Bitmap(64, 64);    // whatever
    bmp.SetResolution(96, 96);          // whatever
    float fontSize = 32f;               // whatever

    using ( Graphics g = Graphics.FromImage(bmp))
    using ( GraphicsPath GP = new GraphicsPath())
    using ( FontFamily fontF = new FontFamily("Arial"))
    {
        testPattern(g, bmp.Size);      // optional

        GP.AddString(text, fontF, 0, fontSize, Point.Empty,
                     StringFormat.GenericTypographic);
        // this is the net bounds without any whitespace:
        Rectangle br = Rectangle.Round(GP.GetBounds());

        g.DrawRectangle(Pens.Red,br); // just for testing

        // now we center:
        g.TranslateTransform( (bmp.Width - br.Width )  / 2 - br.X,
                              (bmp.Height - br.Height )/ 2 - br.Y);
        // and fill
        g.FillPath(Brushes.Black, GP);
        g.ResetTransform();
    }

    // whatever you want to do..
    pictureBox1.Image = bmp;
    bmp.Save("D:\\__test.png", ImageFormat.Png);

}

A small test routine to let us see the centering better:

void testPattern(Graphics g, Size sz)
{
    List<Brush> brushes = new List<Brush>() 
    {   Brushes.SlateBlue, Brushes.Yellow, 
        Brushes.DarkGoldenrod, Brushes.Lavender };
    int bw2 = sz.Width / 2;
    int bh2 = sz.Height / 2;
    for (int i = bw2; i > 0; i--)
        g.FillRectangle(brushes[i%4],bw2 - i, bh2 - i, i + i, i + i );

}

The GetBounds method returns a RectangleF; in my example it is {X=0.09375, Y=6.0625, Width=21, Height=22.90625}. Do note that due to rounding things can always be off by one..

You may or may not want to change the Graphics setting to special Smoothingmodes etc..

Also it should be noted that this will do automatic ie mechanical centering by the bounds rectangle. This may be quite different from 'optical or visual centering', which is rather hard to code and to some extent a matter of personal taste. But typography is as much an art as a profession..

来源：https://stackoverflow.com/questions/33148543/how-to-draw-a-string-at-an-exact-pixel-position

标签

.net

graphics

bitmap

drawstring