c# write text on bitmap

Question

I have following problem. I want to make some graphics in c# windows form. I want to read bitmap to my program and after it write some text on this bitmap. In the end I want this picture load to pictureBox. And it's my question. How can I do it?

example, how must it work:

Bitmap a = new Bitmap(@"path\picture.bmp");
a.makeTransparent();
// ? a.writeText("some text", positionX, positionY);
pictuteBox1.Image = a;

Is it possible do to?

Answer 1

Very old question, but just had to build this for an app today and found the settings shown in other answers do not result in a clean image (possibly as new options were added in later .Net versions).

Assuming you want the text in the centre of the bitmap, you can do this:

// Load the original image
Bitmap bmp = new Bitmap("filename.bmp");

// Create a rectangle for the entire bitmap
RectangleF rectf = new RectangleF(0, 0, bmp.Width, bmp.Height);

// Create graphic object that will draw onto the bitmap
Graphics g = Graphics.FromImage(bmp);

// ------------------------------------------
// Ensure the best possible quality rendering
// ------------------------------------------
// The smoothing mode specifies whether lines, curves, and the edges of filled areas use smoothing (also called antialiasing). 
// One exception is that path gradient brushes do not obey the smoothing mode. 
// Areas filled using a PathGradientBrush are rendered the same way (aliased) regardless of the SmoothingMode property.
g.SmoothingMode = SmoothingMode.AntiAlias;

// The interpolation mode determines how intermediate values between two endpoints are calculated.
g.InterpolationMode = InterpolationMode.HighQualityBicubic;

// Use this property to specify either higher quality, slower rendering, or lower quality, faster rendering of the contents of this Graphics object.
g.PixelOffsetMode = PixelOffsetMode.HighQuality;

// This one is important
g.TextRenderingHint = TextRenderingHint.AntiAliasGridFit;

// Create string formatting options (used for alignment)
StringFormat format = new StringFormat()
{
    Alignment = StringAlignment.Center,
    LineAlignment = StringAlignment.Center
};

// Draw the text onto the image
g.DrawString("yourText", new Font("Tahoma",8), Brushes.Black, rectf, format);

// Flush all graphics changes to the bitmap
g.Flush();

// Now save or use the bitmap
image.Image = bmp;

References

• https://msdn.microsoft.com/en-us/library/system.drawing.graphics.smoothingmode(v=vs.110).aspx
• https://msdn.microsoft.com/en-us/library/system.drawing.drawing2d.interpolationmode(v=vs.110).aspx
• https://msdn.microsoft.com/en-us/library/system.drawing.graphics.pixeloffsetmode(v=vs.110).aspx
• https://msdn.microsoft.com/en-us/library/system.drawing.graphics.textrenderinghint(v=vs.110).aspx
• https://msdn.microsoft.com/en-us/library/system.drawing.stringformat(v=vs.110).aspx
• https://msdn.microsoft.com/en-us/library/21kdfbzs(v=vs.110).aspx

Answer 2

Bitmap bmp = new Bitmap("filename.bmp");

RectangleF rectf = new RectangleF(70, 90, 90, 50);

Graphics g = Graphics.FromImage(bmp);

g.SmoothingMode = SmoothingMode.AntiAlias;
g.InterpolationMode = InterpolationMode.HighQualityBicubic;
g.PixelOffsetMode = PixelOffsetMode.HighQuality;
g.DrawString("yourText", new Font("Tahoma",8), Brushes.Black, rectf);

g.Flush();

image.Image=bmp;

Answer 3

You need to use the Graphics class in order to write on the bitmap.

Specifically, one of the DrawString methods.

Bitmap a = new Bitmap(@"path\picture.bmp");

using(Graphics g = Graphics.FromImage(a))
{
  g.DrawString(....); // requires font, brush etc
}

pictuteBox1.Image = a;