在C#中动态在屏幕上绘制填充矩形 [英] Draw a fill rectangle dynamically on screen in C#

问题描述

我想在屏幕上动态绘制一个填充矩形，其不透明度为0.1.问题是当我移动鼠标时，先前的矩形不清晰.

I would like to draw a fill rectangle dynamically on my screen, with an opacity at 0.1. The problem is that when i move the mouse, the previous rectangles aren't clear.

这是绘制方法.

    private void OnMouseDown(object sender, MouseEventArgs e)
    {
        isMouseDown = true;
        x = e.X;
        y = e.Y;

        g = this.selectorForm.CreateGraphics();
    }

    private void OnMouseMove(object sender, MouseEventArgs e)
    {
        if (!isMouseDown) return;

        this.selectorForm.Invalidate();
        g.FillRectangle(brush, this.getRectangle(x, y, e.X, e.Y));
        g.DrawRectangle(pen, this.getRectangle(x, y, e.X, e.Y));

    }

这是我的选择器表单

    internal class SelectorForm : Form
    {
        protected override void OnPaintBackground(PaintEventArgs e)
        {
        }
    }

绘制矩形(几个重叠矩形)的示例

并且Invalidate()不起作用，因为我覆盖了OnPaintBackground.但是，如果我不执行此覆盖，则在执行this.selectorForm.Show()时，我的屏幕变成灰色.

And Invalidate() doesn't work because I override OnPaintBackground. But if I don't do this override, when I do this.selectorForm.Show(), my screen becomes gray.

那么如何在屏幕上绘制不透明度为0.1的矩形?

So how can I draw a rectangle with an opacity 0.1 on my screen?

谢谢！

推荐答案

这是一个对我有用的示例.

This is an example that works for me.

关键部分是:

• 使用Paint事件及其事件 Graphics
• 添加Clear(BackgroundColor)否则我会得到与您看到的相同的工件
• 为了透明起见，应使用TransparencyKey属性.有一定的颜色选择:
  • 常用颜色可能与表单上的其他内容冲突
  • 倒挂金钟可以奏效，如果您要点击表格
  • 其他不太常见的颜色也适用；我选择了浅绿色
  • using the Paint event and its Graphics
  • adding a Clear(BackgroundColor) or else I get the same artifacts you see
  • for transparency the TransparencyKey property should be used. There is a certain choice of colors:
    • Common colors may conflict with other things on the Form
    • Fuchsia works if you want to click through the Form
    • Other not so common colors are suitable; I chose a light green

    您可能想适应事件的设置方式，我只是这样做，以便进行更快的测试.

    You may want to adapt to your way of setting up events, I just did it this way for faster testing.

    public partial class Form2 : Form
    {
        public Form2()
        {
            InitializeComponent();
            DoubleBuffered = true;
            Opacity = 0.1f;
            // a color that will allow using the mouse on the form:
            BackColor = Color.GreenYellow;
            TransparencyKey = BackColor;
        }
    
        Point mDown = Point.Empty;
        Point mCur = Point.Empty;
    
        private void Form2_MouseDown(object sender, MouseEventArgs e)
        {
            mDown = e.Location;
        }
    
        private void Form2_MouseUp(object sender, MouseEventArgs e)
        {
            mDown = Point.Empty;
        }
    
        private void Form2_MouseMove(object sender, MouseEventArgs e)
        {
            if (e.Button != MouseButtons.Left) return;
            mCur = e.Location;
            Invalidate();
        }
    
        private void Form2_Paint(object sender, PaintEventArgs e)
        {
           if (mDown == Point.Empty) return;
           Size s = new System.Drawing.Size(Math.Abs(mDown.X - mCur.X),
                                            Math.Abs(mDown.Y - mCur.Y)  );
           Point topLeft = new Point(Math.Min(mDown.X, mCur.X), 
                                     Math.Min(mDown.Y, mCur.Y));
           Rectangle r = new Rectangle(topLeft, s);
           e.Graphics.Clear(this.BackColor);                // <--- necessary!
           e.Graphics.FillRectangle(Brushes.Bisque, r );   // <--- pick your..
           e.Graphics.DrawRectangle(Pens.Red, r);         // <--- colors!
        }
    }
    

    }

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