动画 GIF 的帧率似乎低于预期

Question

我有一个winforms 应用程序，上面有一个 gif，可以让用户了解停止进程。

问题在于它的播放速度比在其他应用程序（chrome、Internet Explorer）上看起来要慢得多。

我在PictureBox 和Label 上尝试过gif，但结果速度是一样的。然后经过一点研究，我遇到了this 问题和传奇@Hans Passant 的答案，但不幸的是，应用他建议的样板代码并没有任何区别。

下面是简单的重现代码：

public partial class Form1 : Form
{
    public Form1 ()
    {
        InitializeComponent();
        timeBeginPeriod(timerAccuracy);
    }

    protected override void OnFormClosed ( FormClosedEventArgs e )
    {
        timeEndPeriod(timerAccuracy);
        base.OnFormClosed(e);
    }

    // Pinvoke:
    private const int timerAccuracy = 10;
    [System.Runtime.InteropServices.DllImport("winmm.dll")]
    private static extern int timeBeginPeriod ( int msec );
    [System.Runtime.InteropServices.DllImport("winmm.dll")]
    public static extern int timeEndPeriod ( int msec );
}

如果需要，还有设计器代码：

partial class Form1
{
    private System.ComponentModel.IContainer components = null;

    protected override void Dispose ( bool disposing )
    {
        if (disposing && (components != null))
        {
            components.Dispose();
        }
        base.Dispose(disposing);
    }

    #region Windows Form Designer generated code

    private void InitializeComponent ()
    {
        System.ComponentModel.ComponentResourceManager resources = new System.ComponentModel.ComponentResourceManager(typeof(Form1));
        this.pictureBox1 = new System.Windows.Forms.PictureBox();
        this.label1 = new System.Windows.Forms.Label();
        ((System.ComponentModel.ISupportInitialize)(this.pictureBox1)).BeginInit();
        this.SuspendLayout();
        //
        // pictureBox1
        //
        this.pictureBox1.BorderStyle = System.Windows.Forms.BorderStyle.FixedSingle;
        this.pictureBox1.Image = ((System.Drawing.Image)(resources.GetObject("pictureBox1.Image")));
        this.pictureBox1.Location = new System.Drawing.Point(8, 9);
        this.pictureBox1.Name = "pictureBox1";
        this.pictureBox1.Size = new System.Drawing.Size(166, 119);
        this.pictureBox1.SizeMode = System.Windows.Forms.PictureBoxSizeMode.CenterImage;
        this.pictureBox1.TabIndex = 0;
        this.pictureBox1.TabStop = false;
        //
        // label1
        //
        this.label1.BorderStyle = System.Windows.Forms.BorderStyle.FixedSingle;
        this.label1.FlatStyle = System.Windows.Forms.FlatStyle.Flat;
        this.label1.Image = ((System.Drawing.Image)(resources.GetObject("label1.Image")));
        this.label1.Location = new System.Drawing.Point(180, 9);
        this.label1.Name = "label1";
        this.label1.Size = new System.Drawing.Size(158, 119);
        this.label1.TabIndex = 1;
        //
        // Form1
        //
        this.AutoScaleDimensions = new System.Drawing.SizeF(6F, 13F);
        this.AutoScaleMode = System.Windows.Forms.AutoScaleMode.Font;
        this.ClientSize = new System.Drawing.Size(346, 134);
        this.Controls.Add(this.label1);
        this.Controls.Add(this.pictureBox1);
        this.Name = "Form1";
        this.Text = "Form1";
        ((System.ComponentModel.ISupportInitialize)(this.pictureBox1)).EndInit();
        this.ResumeLayout(false);

    }

    #endregion

    private System.Windows.Forms.PictureBox pictureBox1;
    private System.Windows.Forms.Label label1;
}

两个 gif 以相同的速度播放，但低于实际 gif。在应用此代码时，我还有什么需要注意的吗？

Answer 1

你只能猜测，我怀疑有人会很幸运地得到复制：

• timeBeginPeriod() 在技术上可能会失败，尽管当您要求 10 毫秒时这是非常不寻常的，但请验证它是否返回 0。
• 如果图像很大，那么它可能无法足够快地更新。或者您的 UI 线程忙于其他职责。 gif 的像素格式与现代机器上视频适配器的像素格式不匹配。每次更新帧时都会完成转换。它相当昂贵，尤其是如果您还强制重新缩放图像（即 PictureBox.SizeMode ！= Normal）。使用任务管理器验证您的 UI 线程没有燃烧 100% 内核。
• 您可以通过在提升的命令提示符下运行powercfg /energy 来获得有关有效计时器周期的第二个意见。在您的应用程序运行时执行此操作。它会运行一分钟，然后生成一个 HTML 文件，您可以使用浏览器查看该文件。在“Platform Timer Resolution:Timer Request Stack”标题下报告，Requested Period 值应为 10000。请注意其他进程或驱动程序也可能已发出请求。

Answer 2

2021-04-02 更新

PictureBox 以低帧速率制作动画的根本原因是它在幕后使用了 ImageAnimator 类，而该类仅以 20 FPS 进行动画处理。它在这里的工作线程方法中有一个硬编码的 50ms Thread.Sleep()：

https://referencesource.microsoft.com/#System.Drawing/commonui/System/Drawing/ImageAnimator.cs,333

在编写以下内容时，我最初无法访问 Windows 窗体源，但现在我可能会继承 PictureBox 并使其使用不同的 ImageAnimator 实现以将 Thread.Sleep() 减少到合理的价值。 （ImageAnimator 是一个密封类，因此您必须将代码复制到一个新类中并在您的 PictureBox 中引用它以获得更流畅的动画。）

原答案：

PictureBox 是一个相当重量级的控件，我建议使用类似Panel 的东西来代替您的动画 GIF。此外，我了解到PictureBox 的内部动画计时器分辨率较低，这意味着选择

相反，您可以自己控制绘画和动画。这使用了 PInvoke，因为它利用了一些内核计时器方法。示例代码如下：

using System;
using System.Diagnostics;
using System.Drawing;
using System.Drawing.Imaging;
using System.Runtime.InteropServices;
using System.Windows.Forms;

...

public partial class Form1 : Form
{
    [DllImport("kernel32.dll")]
    static extern bool CreateTimerQueueTimer(out IntPtr phNewTimer,
        IntPtr TimerQueue, WaitOrTimerDelegate Callback, IntPtr Parameter,
        uint DueTime, uint Period, uint Flags);
    [DllImport("kernel32.dll")]
    static extern bool ChangeTimerQueueTimer(IntPtr TimerQueue, IntPtr Timer,
        uint DueTime, uint Period);
    [DllImport("kernel32.dll")]
    static extern bool DeleteTimerQueueTimer(IntPtr TimerQueue, 
        IntPtr Timer, IntPtr CompletionEvent);
    public delegate void WaitOrTimerDelegate(IntPtr lpParameter, 
        bool TimerOrWaitFired);

    // Holds a reference to the function to be called when the timer
    // fires
    public static WaitOrTimerDelegate UpdateFn;

    public enum ExecuteFlags
    {
        /// <summary>
        /// The callback function is queued to an I/O worker thread. This flag should be used if the function should be executed in a thread that waits in an alertable state.
        /// The callback function is queued as an APC. Be sure to address reentrancy issues if the function performs an alertable wait operation.
        /// </summary>
        WT_EXECUTEINIOTHREAD = 0x00000001,
    };

    private Image gif;
    private int frameCount = -1;
    private UInt32[] frameIntervals;
    private int currentFrame = 0;
    private static object locker = new object();
    private IntPtr timerPtr;

    public Form1()
    {
        InitializeComponent();
        // Attempt to reduce flicker - all control painting must be
        // done in overridden paint methods
        this.SetStyle(ControlStyles.AllPaintingInWmPaint |
            ControlStyles.OptimizedDoubleBuffer, true);
        // Set the timer callback
        UpdateFn = new WaitOrTimerDelegate(UpdateFrame);
    }

    private void Form1_Load(object sender, EventArgs e)
    {
        // Replace this with whatever image you're animating
        gif = (Image)Properties.Resources.SomeAnimatedGif;
        // How many frames of animation are there in total?
        frameCount = gif.GetFrameCount(FrameDimension.Time);
        // Retrieve the frame time property
        PropertyItem propItem = gif.GetPropertyItem(20736);
        int propIndex = 0;
        frameIntervals = new UInt32[frameCount];
        // Each frame can have a different timing - retrieve each of them
        for (int i = 0; i < frameCount; i++)
        {
            // NB: intervals are given in hundredths of a second, so need
            // multiplying to match the timer's millisecond interval
            frameIntervals[i] = BitConverter.ToUInt32(propItem.Value, 
                propIndex) * 10;
            // Point to the next interval stored in this property
            propIndex += 4;
        }

        // Show the first frame of the animation
        ShowFrame();
        // Start the animation. We use a TimerQueueTimer which has better
        // resolution than Windows Forms' default one. It should be used
        // instead of the multimedia timer, which has been deprecated
        CreateTimerQueueTimer(out this.timerPtr, IntPtr.Zero, UpdateFn, 
            IntPtr.Zero, frameIntervals[0], 100000,
            (uint)ExecuteFlags.WT_EXECUTEINIOTHREAD);
    }

    private void UpdateFrame(IntPtr lpParam, bool timerOrWaitFired)
    {
        // The timer has elapsed
        // Update the number of the frame to show next
        currentFrame = (currentFrame + 1) % frameCount;
        // Paint the frame to the panel
        ShowFrame();
        // Re-start the timer after updating its interval to that of
        // the new frame
        ChangeTimerQueueTimer(IntPtr.Zero, this.timerPtr,
            frameIntervals[currentFrame], 100000);
    }

    private void ShowFrame()
    {
        // We need to use a lock as we cannot update the GIF at the
        // same time as it's being drawn
        lock (locker)
        {
            gif.SelectActiveFrame(FrameDimension.Time, currentFrame);
        }

        this.panel1.Invalidate();
    }

    private void panel1_Paint(object sender, PaintEventArgs e)
    {
        base.OnPaint(e);

        lock (locker)
        {
            e.Graphics.DrawImage(gif, panel1.ClientRectangle);
        }
    }

    private void Form1_FormClosing(object sender, FormClosingEventArgs e)
    {
        DeleteTimerQueueTimer(IntPtr.Zero, timerPtr, IntPtr.Zero);
    }
}

注意：我们将计时器调用上的Period 设置为100000，因为如果您将其设置为0（表示一次性计时），即使您随后调用@，它也只会触发一次987654337@.

计时器仍然不适合超精确的计时，但这仍然应该比PictureBox 提供更快的更新。