WPF 截图控件之绘制箭头(六)「仿微信」

前言

接着上周写的 绘制箭头继续更新。

1.WPF实现截屏「仿微信」
2.WPF 实现截屏控件之移动（二）「仿微信」
3.WPF 截图控件之伸缩(三) 「仿微信」
4.WPF 截图控件之绘制方框与椭圆(四) 「仿微信」
5.WPF 截图控件之绘制箭头(五)「仿微信」

正文

一、在绘制箭头的时候鼠标的当前Point超出Rect的区域时就不对了。所以需要做计算求相似点转换公式如下

公式代码

—

代码如下

                if (drawArrow.Left <= rect.Left)
                {
                    var a = rect.Left - pointStart.X;
                    var d = current.X - rect.Left;
                    var bc = current.Y - pointStart.Y;
                    var c = bc / (a / d + 1);
                    var b = a / d * c;

                    if (current.Y > pointStart.Y)
                        current.Y = pointStart.Y + b;
                    else
                        current.Y = pointStart.Y - b;
                    current.X = pointStart.X + a;
                }
                else if (drawArrow.Right >= rect.Right)
                {
                    var a = rect.Right - pointStart.X;
                    var d = current.X - rect.Right;
                    var bc = current.Y - pointStart.Y;
                    var c = bc / (a / d + 1);
                    var b = a / d * c;
                    if (current.Y > pointStart.Y)
                        current.Y = pointStart.Y + b;
                    else
                        current.Y = pointStart.Y - b;
                    current.X = pointStart.X + a;
                }
                else if (drawArrow.Top <= rect.Top)
                {
                    var a = pointStart.Y - rect.Top;
                    var d = rect.Top - current.Y;
                    var bc = current.X - pointStart.X;
                    var c = bc / (a / d + 1);
                    var b = a / d * c;



                    if (current.X > pointStart.X)
                        current.X = pointStart.X + b;
                    else
                        current.X = pointStart.X - b;
                    current.Y = pointStart.Y;
                }
                else if (drawArrow.Bottom >= rect.Bottom)
                {
                    var a = rect.Bottom - pointStart.Y;
                    var d = current.Y - rect.Bottom;
                    var bc = current.X - pointStart.X;
                    var c = bc / (a / d + 1);
                    var b = a / d * c;
                    if (current.X > pointStart.X)
                        current.X = pointStart.X + b;
                    else
                        current.X = pointStart.X - b;
                    current.Y = pointStart.Y + a;

                }

如效果如果只是右侧的话判定没问题，如右上或者右下就会判定不对。

 if (current.X < rect.Left
               ||
               current.X > rect.Right
               ||
               current.Y < rect.Top
               ||
               current.Y > rect.Bottom)
            {
                if (current.X >= vPoint.X && current.Y < vPoint.Y)
                {
                    double a1 = (current.Y - vPoint.Y) / (current.X - vPoint.X);
                    double b1 = vPoint.Y - a1 * vPoint.X;
                    double xTop = (rect.Top - b1) / a1;
                    double yRight = a1 * rect.Right + b1;

                    if (xTop <= rect.Right)
                    {
                        current.X = xTop;
                        current.Y = rect.Top;
                    }
                    else
                    {
                        current.X = rect.Right;
                        current.Y = yRight;
                    }
                }
                else if (current.X > vPoint.X && current.Y > vPoint.Y)
                {
                    double a1 = (current.Y - vPoint.Y) / (current.X - vPoint.X);
                    double b1 = vPoint.Y - a1 * vPoint.X;
                    double xBottom = (rect.Bottom - b1) / a1;
                    double yRight = a1 * rect.Right + b1;

                    if (xBottom <= rect.Right)
                    {
                        current.X = xBottom;
                        current.Y = rect.Bottom;
                    }
                    else
                    {
                        current.X = rect.Right;
                        current.Y = yRight;
                    }
                }
                else if (current.X < vPoint.X && current.Y < vPoint.Y)
                {
                    double a1 = (current.Y - vPoint.Y) / (current.X - vPoint.X);
                    double b1 = vPoint.Y - a1 * vPoint.X;
                    double xTop = (rect.Top - b1) / a1;
                    double yLeft = a1 * rect.Left + b1;
                    if (xTop >= rect.Left)
                    {
                        current.X = xTop;
                        current.Y = rect.Top;
                    }
                    else
                    {
                        current.X = rect.Left;
                        current.Y = yLeft;

                    }
                }
                else if (current.X < vPoint.X && current.Y > vPoint.Y)
                {
                    double a1 = (current.Y - vPoint.Y) / (current.X - vPoint.X);
                    double b1 = vPoint.Y - a1 * vPoint.X;
                    double xBottom = (rect.Bottom - b1) / a1;
                    double yLeft = a1 * rect.Left + b1;

                    if (xBottom <= rect.Left)
                    {
                        current.X = rect.Left;
                        current.Y = yLeft;
                    }
                    else
                    {
                        current.X = xBottom;
                        current.Y = rect.Bottom;
                    }
                }
            }