C# と VB.NET の質問掲示板

■No98483 (魔界の仮面弁士 さん) に返信

なんか面白そうなのでボール画像を作って 20 個ほど動かしてみました。
ちょっとカクつくかなーという気がしますが、ちらつきはしないと思います。

using System;
using System.Collections.Generic;
using System.Drawing;
using System.Windows.Forms;

public partial class Form2 : Form
{
    public Form2()
    {
        InitializeComponent();
    }

    Bitmap ballBmp;
    List<CBall> balls;

    private void Form2_Load(object sender, EventArgs e)
    {
        pictureBox1.BackgroundImage = new Bitmap(@"D:\TEST\back.jpg");
        ballBmp = new Bitmap(300, 300);
        using (var g = Graphics.FromImage(ballBmp))
        {
            g.Clear(Color.Black);
            g.FillEllipse(Brushes.Brown, new Rectangle(1, 1, ballBmp.Width - 2, ballBmp.Height - 2));
            g.FillEllipse(Brushes.MistyRose, new Rectangle(4, 4, ballBmp.Width - 8, ballBmp.Height - 8));

            using (var titleFont = new Font("MS UI Gothic", 40, FontStyle.Bold))
            {
                const string title = "\u308F\u3093\u304F\u307E\u540C\u76DF";
                var sz = g.MeasureString(title, titleFont);
                var location = new Point((int)((ballBmp.Width - sz.Width) / 2), (int)((ballBmp.Height - sz.Height) / 2));
                g.DrawString(title, titleFont, Brushes.Brown, location);
            }
        }
        ballBmp.MakeTransparent(Color.Black);

        balls = new List<CBall>();
        for (int i = 0; i < 20; i++)
        {
            CBall ball = new CBall(ballBmp, ClientSize);
            balls.Add(ball);
        }

        timer1.Interval = 16;
        timer1.Enabled = true;
    }

    private void timer1_Tick(object sender, EventArgs e)
    {
        pictureBox1.Invalidate();
    }

    private void pictureBox1_Paint(object sender, PaintEventArgs e)
    {
        foreach (var ball in balls)
        {
            ball.Draw(e.Graphics, pictureBox1.ClientRectangle);
        }
    }

    class CBall
    {
        readonly Bitmap ballBmp;
        readonly Size size;
        readonly int mag;
        int left, top, dx, dy;

        const int MinBallSize = 100;
        const int MaxBallSize = 300;
        static Random random = new Random();

        public CBall(Bitmap bmp, Size clientSize)
        {
            ballBmp = bmp;
            int height = random.Next(MinBallSize, MaxBallSize);
            size = new Size(height, height);
            mag = random.Next(10, 20);
            left = random.Next(10, clientSize.Width);
            top = random.Next(10, clientSize.Height);
            dx = random.Next(0, 2) * 2 - 1;
            dy = random.Next(0, 2) * 2 - 1;
        }

        private Rectangle NextRectangle(Rectangle drawArea)
        {
            left += mag * dx;
            top += (int)(mag * mag * 0.1) * dy;

            if (left + size.Width > drawArea.Right)
            {
                dx = -1 * Math.Abs(dx);
                left += mag * dx;
            }
            if (left < drawArea.Left)
            {
                dx = Math.Abs(dx);
                left += mag * dx;
            }
            if (top + size.Height > drawArea.Bottom)
            {
                dy = -1 * Math.Abs(dy);
                top += (int)(mag * mag * 0.1) * dy;
            }
            if (top < drawArea.Top)
            {
                dy = Math.Abs(dy);
                top += (int)(mag * mag * 0.1) * dy;
            }
            return new Rectangle(left, top, size.Width, size.Height);
        }

        public void Draw(Graphics graphics, Rectangle drawArea)
        {
            var rect = NextRectangle(drawArea);
            graphics.DrawImage(ballBmp, rect);
        }
    }
}