如何将图形转换为位图并将其保存在 c# 中？

Question

currently I am learning to draw barcode using graphics method and dispose it as bitmap. But when I going to save it, although it cans save successfully, but the result is black image, nothing can be seen from that. What is the problem going on?

    private void buttonDraw_Click(object sender, EventArgs e)
    {
        System.Drawing.Graphics g = this.pictureBoxBarcode.CreateGraphics();
        g.FillRectangle(new System.Drawing.SolidBrush(System.Drawing.SystemColors.Control),
        new Rectangle(0, 0, pictureBoxBarcode.Width, pictureBoxBarcode.Height));
        ean13.DrawEan13Barcode(g, new System.Drawing.Point(0, 0));
        g.Dispose();

    }

And this is my save function

    public void Save(Bitmap original)
    {
        // Displays a SaveFileDialog so the user can save the Image
        // assigned to Button2.
        SaveFileDialog saveFileDialog1 = new SaveFileDialog();
        saveFileDialog1.Filter = "JPeg Image|*.jpg|Bitmap Image|*.bmp|Gif Image|*.gif|Png Image|*.png";
        saveFileDialog1.Title = "Save an Image File";
        saveFileDialog1.ShowDialog();

        // If the file name is not an empty string open it for saving.
        if (saveFileDialog1.FileName != "")
        {
            // Saves the Image via a FileStream created by the OpenFile method.
            System.IO.FileStream fs =
               (System.IO.FileStream)saveFileDialog1.OpenFile();
            // Saves the Image in the appropriate ImageFormat based upon the
            // File type selected in the dialog box.
            // NOTE that the FilterIndex property is one-based.

            switch (saveFileDialog1.FilterIndex)
            {
                case 1:
                    original.Save(fs,
                       System.Drawing.Imaging.ImageFormat.Jpeg);
                    break;

                case 2:
                    original.Save(fs,
                       System.Drawing.Imaging.ImageFormat.Bmp);
                    break;

                case 3:
                    original.Save(fs,
                       System.Drawing.Imaging.ImageFormat.Gif);
                    break;

                case 4:
                    original.Save(fs,
                       System.Drawing.Imaging.ImageFormat.Png);
                    break;
            }
            fs.Close();
        }
    }

I cant provide any picture to proof that as my reputation is not enough to do so. Sorry.

Answer 1

To draw into a Bitmap use this code:

private void buttonDraw_Click(object sender, EventArgs e)
{
    Bitmap bmp = new Bitmap(pictureBoxBarcode.ClientSize.Width,
                            pictureBoxBarcode.ClientSize.Height);
    using (Graphics g = Graphics.FromImage(bmp))
    {
       g.Clear(SystemColors.Control);
       ean13.DrawEan13Barcode(g, new System.Drawing.Point(0, 0));
    }
    // display:
    pictureBoxBarcode.Image = bmp;
    // save:
    bmp.Save(yourfilename,  ImageFormat.Png);
    // ..or..: 
    Save(bmp);
}

Or:

private void buttonSave_Click(object sender, EventArgs e)
{
    Save( (Bitmap) pictureBoxBarcode.Image);
}

I have copied your drawing code.

I don't know why you want to make it look gray..?

I am assuming that ean13.DrawEan13Barcode is a function that uses the passed-in Graphics object to draw something onto the Bitmap that is associated with the Graphics object.