球形圖

生成後的圖

1、準備一張球形圖 圖片
2、將球形圖繪製成羅盤圖

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Drawing;
using System.IO;

namespace App
{
    // 生成羅盤圖
    public class Generate
    {
        public Bitmap img = null;

        public Generate()
        {
        }

        ///
 
 <summary>
        /// 繪製羅盤圖
        /// </summary>
        /// <param name="oldim">球形圖</param>
        /// <param name="width">寬度</param>
        public void GraphicsImg(string oldim,int width = 400)
        {
            Bitmap oldimg = new Bitmap(oldim);
            GenerateBgImg(width, width);
            var
 
 r = width * 0.5;
            int oldheight = oldimg.Height;
            int oldwidth = oldimg.Width;
            for (int y = 0; y < width; y++){
                for (int x = 0; x < width; x++){
                    var px = x / width;
                    var d = (x - r + 0.5) * (x - r + 0.5) + (y - r + 0.5
 
) * (y - r + 0.5);
                    d = System.Math.Sqrt(d);
                    var dx = System.Math.Abs(d - r);
                    if (d < r){
                        var BY = System.Math.Floor(oldheight * (1 - d / r));
                        var vx = x + 0.5 - r;
                        var vy = (y + 0.5 - r);
                        var vl = System.Math.Sqrt(vx * vx + vy * vy);
                        var v = (System.Math.Acos(vx / vl));
                        if (vy > 0){
                            v = v + System.Math.PI;
                        }
                        v = v * 180 / System.Math.PI;
                        v = v - 90;
                        if (v < 0){
                            v = v + 360;
                        }
                        var yp = v / 360;
                        var BX = System.Math.Floor(oldwidth * yp);
                        if (vy > 0){
                            BX = oldwidth - BX;
                        }
                        //獲取畫素的ＲＧＢ顏色值
                        Color srcColor = oldimg.GetPixel(Convert.ToInt32(BX), Convert.ToInt32(BY));
                        img.SetPixel(x, y, srcColor);
                        }
                    }
                }
            }
        /// <summary>
        /// 儲存
        /// </summary>
        public void save() {
            img.Save("d:/abc.png", System.Drawing.Imaging.ImageFormat.Png);
        }

        /// <summary>
        /// 建立透明背景圖
        /// </summary>
        /// <param name="width">寬度</param>
        /// <param name="height">高度</param>
        public void GenerateBgImg(int width, int height)
        {
            img = new Bitmap(width, height); 
            Graphics g1 = Graphics.FromImage(img); 
            Color Yourcolor = Color.FromArgb(0, 255, 255, 255);// 透明
            Brush brush = new SolidBrush(Yourcolor);
            g1.FillRectangle(brush, new Rectangle(0, 0, width,height));
        }
    }
}