Remove top and bottom padding from Text drawn on an Image

I propose you a slightly different method, using the GraphicsPath class to both measure and draw the text on a Bitmap object.

The advantage is that the GraphicsPath class reports the actual coordinates where the object(s) that it contains will be drawn and also the size of the text, in relation to a specific Font.
These measures are returned in a RectagleF structure, calling the GraphicsPath.GetBounds() method.
The base constructor assumes a Pen size of 1 pixel.

There’s only one (small) detail to take care of: the GDI+ Bitmap object accepts dimensions expressed in integer values only, while all the other measures are expressed in floating point values.
We need to compensate for the rounding, but it’s usually just ± 1 pixel.

Sample of the results:

A description of the procedure:

• Define a Font Family and Size
• Add the Text string to the GraphicsPath object
• Get the GraphicsPath bounding rectangle of the text object
• Build a Bitmap object using the bounding rectangle Size
• Move the World coordinates, with Graphics.TranslateTransform, to the coordinates defined by the bounding rectangle Y position and the Pen Size, using their negative value: we need to move backwards that measure.
• Draw the Text

See also these notes about GraphicsPath and Fonts:
Properly draw text using Graphics Path

Sample code:

using System.Drawing;
using System.Drawing.Drawing2D;
using System.Drawing.Imaging;
using System.Drawing.Text;


string text = "This is my Text";
Font font = new Font("Arial", 52, FontStyle.Regular, GraphicsUnit.Point);
float penSize = 1f;

using (var path = new GraphicsPath()) {
    path.AddString(text, font.FontFamily, (int)font.Style, font.Size, Point.Empty, StringFormat.GenericTypographic);

    RectangleF textBounds = path.GetBounds();

    using (var bitmap = new Bitmap((int)textBounds.Width, (int)textBounds.Height, PixelFormat.Format32bppArgb))
    using (var g = Graphics.FromImage(bitmap)) 
    using (var brush = new SolidBrush(Color.LightGreen)) {
        g.SmoothingMode = SmoothingMode.AntiAlias;
        // When rendering without a GraphicsPath object
        //g.TextRenderingHint = TextRenderingHint.ClearTypeGridFit;
        g.Clear(Color.Black);
        g.TranslateTransform(-(textBounds.X + penSize), -(textBounds.Y + penSize));
        g.FillPath(brush, path);
        
        bitmap.Save("[Image Path]", ImageFormat.Png);
        // Or: return (Bitmap)bitmap.Clone();
        // Or: return bitmap; declaring the bitmap without the using statement
    }
}