在我的Paint程序中绘制矩形时出错 [英] Bug when drawing rectangles in my Paint Program

问题描述

public partial class Form1 : Form
{
    Point downPoint , upPoint;
    List<Shapes> shapes = new List<Shapes>();
    public ShapesEnum shapeType;

    public Form1()
    {
        InitializeComponent();
    }

    protected override void OnPaint(PaintEventArgs e)
    {
        base.OnPaint(e);
        foreach (var s in shapes)
            s.Draw(e.Graphics);
    }

    protected override void OnMouseDown(MouseEventArgs e)
    {
        downPoint = e.Location;
    }

    protected override void OnMouseUp(MouseEventArgs e)
    {
        base.OnMouseUp(e);
        upPoint = e.Location;
        CreateShape();
        this.Invalidate();
    }

    private void CreateShape()
    {
        if (shapeType == ShapesEnum.Circle)
        {
            Rectangle rect = new Rectangle(downPoint.X, downPoint.Y, upPoint.X - downPoint.X, upPoint.Y - downPoint.Y);
            Ellipse ellipse = new Ellipse() { rect = rect };
            shapes.Add(ellipse);
        }

        else if (shapeType == ShapesEnum.Rectangle)
        {
            Rectangle rect = new Rectangle(downPoint.X, downPoint.Y, upPoint.X - downPoint.X, upPoint.Y - downPoint.Y);
            Rect rectangle = new Rect() { rect = rect };
            shapes.Add(rectangle);
        }

        else if (shapeType == ShapesEnum.Line)
        {
            Point pt1 = new Point (upPoint.X, upPoint.Y);
            Point pt2 = new Point (downPoint.X, downPoint.Y);

            Ln rectangle = new Ln() { PointUp = pt1, PointDown = pt2 };
            shapes.Add(rectangle);
        }
        lblStatus.Text = string.Format("dn:{0} up:{1} ct:{2}", downPoint, upPoint, shapes.Count());
    }

    private void btnCircle_Click(object sender, EventArgs e)
    {
        shapeType = ShapesEnum.Circle;
    }

    private void btnRectangle_Click(object sender, EventArgs e)
    {
        shapeType = ShapesEnum.Rectangle;
    }

    private void btnLine_Click(object sender, EventArgs e)
    {
        shapeType = ShapesEnum.Line;
    }

}

这是目前的主要部分我的绘画程序。

This is currently the main part of my paint program.

public enum ShapesEnum { Circle, Rectangle, Line }
abstract class Shapes
{
    public Rectangle rect { get; set; }
    public Color color { get; set; }
    public bool isFilled { get; set; }
    public abstract void Draw(Graphics g);
}

class Ellipse : Shapes
{
    public override void Draw(Graphics g)
    {
        g.DrawEllipse(Pens.Black, rect);
    }
}

class Rect : Shapes
{
    public override void Draw(Graphics g)
    {
        g.DrawRectangle(Pens.Black, rect);
    }
}

class Ln : Shapes
{
    public Point PointUp { get; set; }
    public Point PointDown { get; set; }

    public override void Draw(Graphics g)
    {
        g.DrawLine(Pens.Black, PointUp, PointDown);
    }
}

这是我的类，用于继承形状。根据形状，将调用其中一个类。

This is my class that is used for inheritance on the shapes. Depending on the shape, one of the classes will be called.

绘图椭圆工作正常。绘制线也一样。但是，在绘制矩形方面存在一个错误。如果我把鼠标拖动并从左到右放开，这将有效。但是，如果我转向另一个方向，它在表单上是不可见的，但 shapes.Count（）仍然会添加到形状列表。

Drawing ovals works fine. Same goes for drawing lines. However, there is a bug when it comes to drawing rectangles. If I put my mouse and drag and let go from left up to bottom right, this will work. However, if I go another direction it is invisible on the form but the shapes.Count() still adds towards the list of shapes.

导致此错误的原因是什么？

What caused this bug?

推荐答案

尝试这样的事情是为了让起点和终点正确：

Try something like this in order to have the start and end points the right way:

int x0 = Math.Min(upPoint.X, downPoint.X);
int y0 = Math.Min(upPoint.Y, downPoint.Y);
Point upperLeft = new Point(x0, y0);

int x1 = Math.Max(upPoint.X, downPoint.X);
int y1 = Math.Max(upPoint.Y, downPoint.Y);
Point lowerRight = new Point(x1, y1);

和

Rectangle rect = new Rectangle(x0, y0, x1 - x0, y1 - y0);

这篇关于在我的Paint程序中绘制矩形时出错的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！