Question

C# Graphics绘图的问题

Graphics g = Graphics.FromHwnd(pictureBox1.Handle);
g.Clear(Color.Transparent);

想要去除onpaint画的图(不是去Image)..用上面的代码搞得背景变全黑 怎么办
......我想清除绘面然后用透明色填充 但是g.Clear(Color.Transparent); 这样写会背景全黑 有没有什么办法能不全黑的

Answer 1

先保存原图
清空的时候把原图给画上就行了
代码

public partial class Form1 : Form
{
public Form1()
{
InitializeComponent();
}
private Image img;
private void 清空旧方法_Click(object sender, EventArgs e)
{
Graphics g = Graphics.FromHwnd(pictureBox1.Handle);
g.Clear(Color.Green);
}

private void Form1_Load(object sender, EventArgs e)
{
img = pictureBox1.Image; //保存原图
}

private void 清空_Click(object sender, EventArgs e)
{
Graphics g = Graphics.FromHwnd(pictureBox1.Handle);
g.DrawImage(img,new Point(0,0));
}

}

Answer 2

你要设置透明色。
System .Drawing .Imaging.ImageAttributes imgAttr=new System.Drawing.Imaging.ImageAttributes ();
imgAttr .SetColorKey(pictureBox1 .BackColor ,pictureBox1 .BackColor );
Image img;
e.Graphics.DrawImage(img, desRect, srcRect, GraphicsUnit.Pixel, imgAttr);

Answer 3

重载OnPaint, 换成自己的代码即可。