保存绘制的图像 PictureBox [重复]

Question

我的程序允许用户绘制PictureBox。

我正在尝试将 pictureBox1 保存为 .jpg 文件，但此文件为空。

我的保存按钮：

Bitmap bm = new Bitmap(pictureBox1.ClientSize.Width, pictureBox1.ClientSize.Height);
this.pictureBox1.DrawToBitmap(bm, this.pictureBox1.ClientRectangle);
bm.Save(String.Format("{0}.jpg", this.ID));
this.pictureBox1.CreateGraphics().Clear(Color.White);

我的抽奖活动：

private void pictureBox1_MouseDown(object sender, MouseEventArgs e)
{
    drawNote.isDraw = true;
    drawNote.X = e.X;
    drawNote.Y = e.Y;
}

private void pictureBox1_MouseMove(object sender, MouseEventArgs e)
{
    if(drawNote.isDraw)
    {
        Graphics G = pictureBox1.CreateGraphics();
        G.DrawLine(drawNote.pen, drawNote.X, drawNote.Y, e.X, e.Y);

        drawNote.X = e.X;
        drawNote.Y = e.Y;

    }
}

Answer 1

你应该通过这个位图创建一个空的Bimap set pictureBox1.Image 然后从中创建graphics，并且你必须将它存储在全局变量中以防止重新创建它。

像这样：

Graphics graphics = null;
private void pictureBox1_MouseMove(object sender, MouseEventArgs e)
{
    if(drawNote.isDraw)
    {
        if (graphics == null) 
        {
          graphics = pictureBox1.CreateGraphics();
          Bitmap bmp = new Bitmap(pictureBox1.ClientSize.Width, pictureBox1.ClientSize.Height);
          pictureBox1.Image = bmp;
          graphics = Graphics.FromImage(bmp);
          graphics.Clear(Color.White);
        }

        graphics.DrawLine(drawNote.pen, drawNote.X, drawNote.Y, e.X, e.Y);

        graphics.Flush();
        graphics.Save();
        pictureBox1.Refresh();

        drawNote.X = e.X;
        drawNote.Y = e.Y;
    }
}

你可以通过这个简单的代码来做到这一点：

using (FileStream fileStream = new FileStream(@"C:\test.jpg", FileMode.Create))
{
    pictureBox1.Image.Save(fileStream, System.Drawing.Imaging.ImageFormat.Jpeg);
}