c# - 根据两点旋转图像

Question

我的表单上有两个点和一个图片框，如下所示:

*

   [^]
   [ ]

          *

我想将图片框与点对齐，使其看起来像这样:

*

   \^\
    \ \

          *

如何计算角度以及如何旋转 PictureBox？

目前我正在使用这个:

double xDifference = Math.Abs(point2.X - point1.X);
double yDifference = Math.Abs(point2.Y - point1.Y);

double angle = Math.Atan(yDifference / xDifference) * 180 / Math.PI;

但这不起作用，因为 x 和 y 值是绝对值，因此如果点 2 位于点 1 的左侧，则它们无法计算它。

为了旋转图片，我找到了如下函数:

    public Bitmap rotateImage(Image image, PointF offset, float angle) {
        // Create a new empty bitmap to hold rotated image
        Bitmap rotatedBmp = new Bitmap(image.Width, image.Height);
        rotatedBmp.SetResolution(image.HorizontalResolution, image.VerticalResolution);

        // Make a graphics object from the empty bitmap
        Graphics g = Graphics.FromImage(rotatedBmp);

        // Put the rotation point in the center of the image
        g.TranslateTransform(offset.X, offset.Y);

        // Rotate the image
        g.RotateTransform(angle);

        // Move the image back
        g.TranslateTransform(-offset.X, -offset.Y);

        // Draw passed in image onto graphics object
        g.DrawImage(image, new PointF(0, 0));

        return rotatedBmp;
    }

我将如何使用该功能？我不确定要为偏移量插入什么值。

谢谢

Answer 1

我不喜欢在不必要的时候使用角度。

在这里，您只想改变正交基。

您想从 {X;Y} 移动到 {U;V}，其中 V(范数 1)平行于 AB(或点 1 点 2)。

因为 {U;V} 是正交基，Ux = Vy 且 Uy = -Vx。

using System;
using System.Drawing;
using System.Drawing.Drawing2D;
using System.Windows.Forms;

namespace CsiChart
{
    public partial class CustomControl1 : Control
    {
        private const float EPSILON = 1e-6f;

        private Image _image;
        private ImageLayout _imageLayout = ImageLayout.Center;
        private PointF _pointA = new PointF(0, 100);
        private PointF _pointB = new PointF(100, 0);

        public CustomControl1()
        {
            InitializeComponent();
        }

        public Image Image
        {
            get { return _image; }
            set
            {
                if (Equals(_image, value)) return;
                _image = value;
                Invalidate();
                OnImageChanged(EventArgs.Empty);
            }
        }

        public event EventHandler ImageChanged;

        public ImageLayout ImageLayout
        {
            get { return _imageLayout; }
            set
            {
                if (Equals(_imageLayout, value)) return;
                _imageLayout = value;
                Invalidate();
                OnImageLayoutChanged(EventArgs.Empty);
            }
        }

        public event EventHandler ImageLayoutChanged;

        public PointF PointA
        {
            get { return _pointA; }
            set
            {
                if (Equals(_pointA, value)) return;
                _pointA = value;
                Invalidate();
                OnPointAChanged(EventArgs.Empty);
            }
        }

        public event EventHandler PointAChanged;

        public PointF PointB
        {
            get { return _pointB; }
            set
            {
                if (Equals(_pointB, value)) return;
                _pointB = value;
                Invalidate();
                OnPointBChanged(EventArgs.Empty);
            }
        }

        public event EventHandler PointBChanged;

        protected override void OnPaint(PaintEventArgs pe)
        {
            base.OnPaint(pe);
            if (DesignMode) return;

            var g = pe.Graphics;
            g.Clear(BackColor);         

            var image = Image;
            if (image == null) return;

            var clientRectangle = ClientRectangle;
            var centerX = clientRectangle.X + clientRectangle.Width / 2;
            var centerY = clientRectangle.Y + clientRectangle.Height / 2;

            var srcRect = new Rectangle(new Point(0, 0), image.Size);

            var pointA = PointA;
            var pointB = PointB;

            // Compute U, AB vector normalized.
            var vx = pointB.X - pointA.X;
            var vy = pointB.Y - pointA.Y;
            var vLength = (float) Math.Sqrt(vx*vx + vy*vy);
            if (vLength < EPSILON)
            {
                vx = 0;
                vy = 1;
            }
            else
            {
                vx /= vLength;
                vy /= vLength;
            }

            var oldTransform = g.Transform;

            // Change basis to U,V
            // We also take into acount the inverted on screen Y.
            g.Transform = new Matrix(-vy, vx, -vx, -vy, centerX, centerY);

            var imageWidth = image.Width;
            var imageHeight = image.Height;

            RectangleF destRect;
            switch (ImageLayout)
            {
                case ImageLayout.None:
                    destRect = new Rectangle(0, 0, imageWidth, imageHeight);
                    break;
                case ImageLayout.Center:
                    destRect = new Rectangle(-imageWidth/2, -imageHeight/2, imageWidth, imageHeight);
                    break;
                case ImageLayout.Zoom:
                    // XY aligned bounds size of the image.
                    var imageXSize = imageWidth*Math.Abs(vy) + imageHeight*Math.Abs(vx);
                    var imageYSize = imageWidth*Math.Abs(vx) + imageHeight*Math.Abs(vy);

                    // Get best scale to fit.
                    var s = Math.Min(clientRectangle.Width/imageXSize, clientRectangle.Height/imageYSize);
                    destRect = new RectangleF(-imageWidth*s/2, -imageHeight*s/2, imageWidth*s, imageHeight*s);
                    break;
                default:
                    throw new InvalidOperationException();
            }

            g.DrawImage(image, destRect, srcRect, GraphicsUnit.Pixel);
            g.Transform = oldTransform;
        }

        protected virtual void OnImageChanged(EventArgs eventArgs)
        {
            var handler = ImageChanged;
            if (handler == null) return;
            handler(this, eventArgs);
        }

        protected virtual void OnImageLayoutChanged(EventArgs eventArgs)
        {
            var handler = ImageLayoutChanged;
            if (handler == null) return;
            handler(this, eventArgs);
        }

        private void OnPointAChanged(EventArgs eventArgs)
        {
            var handler = PointAChanged;
            if (handler == null) return;
            handler(this, eventArgs);
        }

        private void OnPointBChanged(EventArgs eventArgs)
        {
            var handler = PointBChanged;
            if (handler == null) return;
            handler(this, eventArgs);
        }
    }
}