How to save drew Graphics of “Paint()” into image using c#?

Question

I actually wanted to Convert RTF into Image so after googling a lot I\'ve got a code that does it by Paint() Event of Picturebox1 and it works perfectly : <

Answer 1

Your code produces an empty image file because you are not drawing anything onto 'newBitmap'.

If you want to draw anything onto 'newBitmap' you need to create a Graphics object from it. As I do not know where 'DrawRtfText' comes from and how it works my guess would be:

private void pictureBox1_Paint(object sender, PaintEventArgs e)
{
        //... 
        Bitmap newBitmap = new Bitmap(pictureBox1.Width, pictureBox1.Height);
        Graphics g = Graphics.FromImage(newBitmap);
        g.DrawRtfText(this.richTextBox1.Rtf, this.pictureBox1.ClientRectangle);
        newBitmap.Save(@"d:\adv.jpg");
}

Answer 2

Disclaimer: I don't have the time to dig into the posted extension method but it is interesting and works well, at least when drawing onto a control surface.

But I could reproduce how bad the results are when drawing into a bitmap..

But: When done right the saved results are excellent!

So here here are a few things to keep in mind:

• Saving in the Paint event is a bad idea, as this event will be triggered by the system whenever it needs to redraw the control; test by doing a minimize/maximize cycle.

• In addition the DrawRtfText semms to create a double-vision effect when drawing into a bitmap.

• So make sure you use DrawToBitmap to grab the results. For this you need to place the call to DrawRtfText in the Paint event of a control!

• Also make sure to have large enough resolutions both in the control (pixel size) and the Bitmap (dpi) to get nice, crispy and (if needed) printable results.

• Do not save to jpg as this is bound to result in blurry text! Png is the format of choice!

Here is a Paint event:

private void panel1_Paint(object sender, PaintEventArgs e)
{
    e.Graphics.Clear(richTextBox1.BackColor);
    e.Graphics.TextRenderingHint = System.Drawing.Text.TextRenderingHint.AntiAlias;
    e.Graphics.SmoothingMode = SmoothingMode.AntiAlias;
    Padding pad = new Padding(120, 230, 10, 30);  // pick your own numbers!
    Size sz = panel1.ClientSize;
    Rectangle rect = new Rectangle(pad.Left, pad.Top, 
                                   sz.Width - pad.Horizontal, sz.Height - pad.Vertical);
    e.Graphics.DrawRtfText(this.richTextBox1.Rtf, rect);            
        
}

Note that it pays to improve on the default quality settings; if you don't the text in the resulting file will break apart when zooming in..

Here is a Save button click:

private void button1_Click(object sender, EventArgs e)
{
    Size sz = panel1.ClientSize;

    // first we (optionally) create a bitmap in the original panel size:
    Rectangle rect1 = panel1.ClientRectangle;
    Bitmap bmp = new Bitmap(rect1.Width, rect1.Height);
    panel1.DrawToBitmap(bmp, rect);
    bmp.Save("D:\\rtfImage1.png", ImageFormat.Png);

    // now we create a 4x larger one:
    Rectangle rect2 = new Rectangle(0, 0, sz.Width * 4, sz.Height * 4);
    Bitmap bmp2 = new Bitmap(rect2.Width, rect2.Height);

    // we need to temporarily enlarge the panel:
    panel1.ClientSize = rect2.Size;

    // now we can let the routine draw
    panel1.DrawToBitmap(bmp2, rect2);
    // and before saving we optionally can set the dpi resolution
    bmp2.SetResolution(300, 300);

    // optionally make background transparent:
    bmp2.MakeTransparent(richTextBox1.BackColor);
    UnSemi(bmp2);  // see the link in the comment!

    // save text always as png; jpg is only for fotos!
    bmp2.Save("D:\\rtfImage2.png", ImageFormat.Png);

    // restore the panels size
    panel1.ClientSize = sz;
}

I found the result to be really good.

Note that DrawToBitmap will internally trigger the Paint event to grab the drawn graphics.

Of course you don't need both parts - use only the one you want (.e. skip the 1st part, between first and now ) and do use your own numbers. It helps to know what the output shall be and calculate the necessary sizes and resolutions backward from there.

I added the enlarged version because usually the monitor resolution, which is what the controls all have, is rather limited, around 75-100dpi, while print quality starts only at 150dpi..

Here is a link to the UnSemi function