C# と VB.NET の質問掲示板

■No50925 (魔界の仮面弁士) に追記
> 方法は幾つかありますが、Timer の Tick イベントで定期的(0.5秒間隔)に
> PictureBox の Invalidate か Refresh を呼ぶようにして、描画処理も
> PictureBox の Paint イベントで、e.Graphics に描画してやれば解決できるかと。

以下、実装例です。

Image img;
int offset, count;
private void Form1_Load(object sender, EventArgs e)
{
    img = Image.FromFile(@"C:\サンプル.jpg");
    timer1.Interval = 250;
}

private void pictureBox1_Click(object sender, EventArgs e)
{
    offset = +1;
    count = 0;
    timer1.Start();
}

private void timer1_Tick(object sender, EventArgs e)
{
    count += offset;

    pictureBox1.Refresh();

    if (count >= 10)
    {
        offset = -1;
    }
    else if (count <= 0)
    {
        timer1.Stop();
    }
}

private void pictureBox1_Paint(object sender, PaintEventArgs e)
{
    if (img != null)
    {
        DrawFadedImage(e.Graphics, img, count * 0.1F);
    }
}

private void Form1_FormClosed(object sender, FormClosedEventArgs e)
{
    if (img != null)
    {
        img.Dispose();
    }
}

■No50927 (魔界の仮面弁士) に追記
> 以下、実装例です。

別案。

private void Form1_Load(object sender, EventArgs e)
{
    backgroundWorker1.WorkerReportsProgress = true;
}

private void pictureBox1_Click(object sender, EventArgs e)
{
    if (!backgroundWorker1.IsBusy)
    {
        Bitmap canvas = new Bitmap(pictureBox1.Width, pictureBox1.Height);
        backgroundWorker1.RunWorkerAsync(canvas);
    }
}

private void backgroundWorker1_ProgressChanged(object sender, ProgressChangedEventArgs e)
{
    pictureBox1.Image = (Image)e.UserState;
}

private void backgroundWorker1_DoWork(object sender, DoWorkEventArgs e)
{
    BackgroundWorker bgw = (BackgroundWorker)sender;
    Bitmap canvas = (Bitmap)e.Argument;

    using (Image img = Image.FromFile(@"C:\サンプル.jpg"))
    using (Graphics g = Graphics.FromImage(canvas))
    {
        for (int i = 1; i <= 10; i++)
        {
            g.Clear(Color.Transparent);
            DrawFadedImage(g, img, i * 0.1F);
            bgw.ReportProgress(0, canvas);
            System.Threading.Thread.Sleep(250);
        }
        for (int i = 9; i >= 0; i--)
        {
            g.Clear(Color.Transparent);
            DrawFadedImage(g, img, i * 0.1F);
            bgw.ReportProgress(0, canvas);
            System.Threading.Thread.Sleep(250);
        }
    }
}