C# getting unusable base64 when converting from bitmap

Question

I'm trying to capture the screen and then output the screenshot as a base64 image but cannot seem to get a usable base64 image out my code.

public static Bitmap bitmap;
    public static string base64;
    public Form1()
    {
        InitializeComponent();
    }
    private void button1_Click(object sender, EventArgs e)
    {
        CaptureScreen();
        Graphics graphics = Graphics.FromImage(bitmap as Image);
        graphics.CopyFromScreen(0, 0, 0, 0, bitmap.Size);
        pictureBox1.SizeMode = PictureBoxSizeMode.StretchImage;
        pictureBox1.Image = bitmap;
        richTextBox1.Text = base64;
    }
    public static string CaptureScreen()
    {
        bitmap = new Bitmap(Screen.PrimaryScreen.Bounds.Width, Screen.PrimaryScreen.Bounds.Height);
        Bitmap bImage = bitmap;
        System.IO.MemoryStream ms = new System.IO.MemoryStream();
        bImage.Save(ms, System.Drawing.Imaging.ImageFormat.Jpeg);
        byte[] byteImage = ms.ToArray();
        base64 = Convert.ToBase64String(byteImage);
        return base64;
    }

I get this output when testing and it should display this or close too this image.

do u mean on graphics.CopyFromScreen(0, 0, 0, 0, bitmap.Size); this is just for displaying what the result should look like. just for development — MrGreyKnight
– MrGreyKnight, Commented May 30, 2017 at 15:58
but: you're allocating an empty bitmap, writing nothing to it, then saving it; you should expect to see a black (or white) rectangle. What do you see? it looks like a black rectangle to me... — Marc Gravell
– Marc Gravell, Commented May 30, 2017 at 16:00
when i convert the base64 string back into an image i get a black square. i get a full working screenshot displayed in the picturebox1 — MrGreyKnight
– MrGreyKnight, Commented May 30, 2017 at 16:02
what did you expect, and why? why would you expect to see anything else? You allocated an empty bitmap, and wrote nothing to it... — Marc Gravell
– Marc Gravell, Commented May 30, 2017 at 16:03

Marc Gravell · Accepted Answer · 2017-05-30 16:07:26Z

2

The problem here is timing.

You are creating the base-64 before you copy the screen into the image; you need to move the line:

graphics.CopyFromScreen(0, 0, 0, 0, bitmap.Size);

to happen before the line:

bImage.Save(ms, System.Drawing.Imaging.ImageFormat.Jpeg);

Try literally just changing it to:

graphics.CopyFromScreen(0, 0, 0, 0, bImage.Size);
bImage.Save(ms, System.Drawing.Imaging.ImageFormat.Jpeg);

answered May 30, 2017 at 16:07

Marc Gravell

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2 Comments

MrGreyKnight Over a year ago

Thank You very much Marc! :D

Nikita Over a year ago

I have searched this question, and in my case I have updated with the line bImage.Save(ms, System.Drawing.Imaging.ImageFormat.Jpeg); the format, I have used .Bmp, changed to .Jpeg and reached the desired output

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