C#使用System.Drawing实现位图取色与绘图的方法

using system;
using system.drawing;
using system.runtime.interopservices;
using system.windows.forms;
public class colorpicker
{
    // 方法一：通过截屏获取指定屏幕坐标的颜色（推荐，更通用）
    public static color getcoloratscreenpoint(point screenpoint)
    {
        // 创建一个1x1像素的位图
        using (bitmap bitmap = new bitmap(1, 1))
        {
            // 使用graphics对象从屏幕指定位置拷贝1个像素 using (graphics g = graphics.fromimage(bitmap))
            {
                g.copyfromscreen(screenpoint, point.empty, new size(1, 1));
            }
            // 返回该像素的颜色
            return bitmap.getpixel(0, 0);
        }
    }
    // 方法二：使用windows api (getpixel) 直接获取（需要引用user32.dll和gdi32.dll）
    [dllimport("user32.dll")]
    private static extern intptr getdc(intptr hwnd);
    [dllimport("user32.dll")]
    private static extern int releasedc(intptr hwnd, intptr hdc);
    [dllimport("gdi32.dll")]
    private static extern uint getpixel(intptr hdc, int nxpos, int nypos);
    public static color getcoloratscreenpoint_api(point screenpoint)
    {
        intptr hdc = getdc(intptr.zero);
        uint pixel = getpixel(hdc, screenpoint.x, screenpoint.y);
        releasedc(intptr.zero, hdc);
        // 将getpixel返回的colorref转换为color对象 byte red = (byte)(pixel & 0x000000ff);
        byte green = (byte)((pixel & 0x0000ff00) >> 8);
        byte blue = (byte)((pixel & 0x00ff0000) >> 16);
        return color.fromargb(red, green, blue);
    }
    // 示例：在定时器或循环中实时获取鼠标位置颜色 public static void startrealtimecolorpick(label colorlabel)
    {
        timer timer = new timer();
        timer.interval = 50; // 每50毫秒更新一次
        timer.tick += (sender, e) =>
        {
            point mousepos = control.mouseposition;
            color color = getcoloratscreenpoint(mousepos);
            colorlabel.text = $"坐标:({mousepos.x},{mousepos.y}), rgb:({color.r},{color.g},{color.b})";
            colorlabel.backcolor = color;
        };
        timer.start();
    }
}

using system.drawing;
using system.drawing.drawing2d;

public class bitmapdrawer
{
    // 方法：在现有位图上绘制一个圆
    public static bitmap drawcircleonbitmap(bitmap originalbitmap, point center, int radius, color circlecolor, int penwidth = 2)
    {
        // 创建原图的副本，避免修改原图 bitmap resultbitmap = new bitmap(originalbitmap);
        using (graphics g = graphics.fromimage(resultbitmap))
        {
            // 设置绘图质量
            g.smoothingmode = smoothingmode.antialias;
            g.interpolationmode = interpolationmode.highqualitybicubic;

            // 创建画笔
            using (pen pen = new pen(circlecolor, penwidth))
            {
                // 计算圆的左上角坐标和直径 rectangle rect = new rectangle(center.x - radius, center.y - radius, radius * 2, radius * 2);
                // 绘制圆 g.drawellipse(pen, rect);
                // 如果需要填充圆，使用 brush
                // using (solidbrush brush = new solidbrush(color.fromargb(50, circlecolor)))
                // {
                //     g.fillellipse(brush, rect);
                // }
            }
        }
        return resultbitmap;
    }

    // 方法：创建一个新的位图并在上面画圆
    public static bitmap createbitmapwithcircle(int width, int height, point center, int radius, color backgroundcolor, color circlecolor)
    {
        bitmap bitmap = new bitmap(width, height);
        using (graphics g = graphics.fromimage(bitmap))
        {
            // 填充背景色 using (solidbrush backgroundbrush = new solidbrush(backgroundcolor))
            {
                g.fillrectangle(backgroundbrush, 0, 0, width, height);
            }
            // 画圆
            using (pen pen = new pen(circlecolor, 3))
            {
                rectangle rect = new rectangle(center.x - radius, center.y - radius, radius * 2, radius * 2);
                g.drawellipse(pen, rect);
            }
        }
        return bitmap;
    }
}

using system;
using system.drawing;
using system.windows.forms;

namespace bitmapsimpledemo
{
    public partial class mainform : form
    {
        private bitmap originalbitmap; // 原始位图 private bitmap displayedbitmap; // 当前显示的位图（可能已画圆）
        private point lastclickpoint;
        private int circleradius = 30;

        public mainform()
        {
            initializecomponent();
            // 加载一张示例图片到picturebox
            originalbitmap = new bitmap(@"你的图片路径.jpg");
            picturebox1.image = originalbitmap;
            displayedbitmap = (bitmap)originalbitmap.clone();
        }

        // picturebox的鼠标点击事件 private void picturebox1_mouseclick(object sender, mouseeventargs e)
        {
            if (originalbitmap == null) return;

            lastclickpoint = e.location;

            // 1. 获取点击位置的颜色
            color clickedcolor = originalbitmap.getpixel(e.x, e.y);
            lblcolorinfo.text = $"点击点颜色 - r:{clickedcolor.r} g:{clickedcolor.g} b:{clickedcolor.b}";
            pnlcolorpreview.backcolor = clickedcolor;

            // 2. 在 displayedbitmap 上以点击点为中心画圆
            // 先重置为原图
            displayedbitmap?.dispose();
            displayedbitmap = (bitmap)originalbitmap.clone();

            using (graphics g = graphics.fromimage(displayedbitmap))
            {
                g.smoothingmode = system.drawing.drawing2d.smoothingmode.antialias;
                // 使用与取色形成对比的颜色画圆，例如取反色 color drawcolor = color.fromargb(255 - clickedcolor.r, 255 - clickedcolor.g, 255 - clickedcolor.b);
                using (pen pen = new pen(drawcolor, 3))
                {
                    rectangle rect = new rectangle(e.x - circleradius, e.y - circleradius, circleradius * 2, circleradius * 2);
                    g.drawellipse(pen, rect);
                }
            }

            // 3. 更新picturebox显示 picturebox1.image = displayedbitmap;
        }

        // 按钮：保存画了圆的图片 private void btnsave_click(object sender, eventargs e)
        {
            if (displayedbitmap != null)
            {
                savefiledialog sfd = new savefiledialog();
                sfd.filter = "png image|*.png|jpeg image|*.jpg";
                if (sfd.showdialog() == dialogresult.ok)
                {
                    displayedbitmap.save(sfd.filename);
                }
            }
        }

        // 按钮：重置图片，清除所有圆圈 private void btnreset_click(object sender, eventargs e)
        {
            displayedbitmap?.dispose();
            displayedbitmap = (bitmap)originalbitmap.clone();
            picturebox1.image = displayedbitmap;
            lblcolorinfo.text = "颜色信息";
            pnlcolorpreview.backcolor = systemcolors.control;
        }

        // 窗体关闭时释放资源
        private void mainform_formclosing(object sender, formclosingeventargs e)
        {
            originalbitmap?.dispose();
            displayedbitmap?.dispose();
        }
    }
}