动画 GIF 帧速率似乎低于预期
Animated GIF's framerate seems lower than expected
我有一个 winforms 应用程序，上面有一个 gif，让用户了解进程停滞。
问题是它的播放速度比在其他应用程序（chrome、Internet Explorer）上看起来慢得多。
我已经在 PictureBox 和 Label 上尝试了 gif，但结果速度是一样的。然后经过一些研究，我遇到了 this 传奇人物@Hans Passant 的问题和答案，但不幸的是，应用他建议的样板代码没有任何区别。
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 的播放速度相同，但低于实际 gif。应用此代码时还有其他需要注意的地方吗？
你只能猜测，我怀疑任何人都不会很幸运地得到一个重现：
- 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，请验证它 returns 0。
- 如果图片很大，那么更新速度可能不够快。或者您的 UI 线程被其他任务占用了太多。 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。每次更新帧时都会进行转换。这是相当昂贵的，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 线程未消耗 100% 核心。
- 您可以通过提升的命令提示符 运行
powercfg /energy 获得关于有效计时器周期的第二个意见。在您的应用 运行 时执行此操作。它会滚动一分钟，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发出请求。
更新2021-04-02
PictureBox 以低帧率设置动画背后的根本原因是因为它在幕后使用了 ImageAnimator class，它仅以 20 FPS 设置动画。它在此处的工作线程方法中有一个硬编码的 50 毫秒 Thread.Sleep()：
https://referencesource.microsoft.com/#System.Drawing/commonui/System/Drawing/ImageAnimator.cs,333
最初在编写以下内容时我无法访问 Windows 表单源，但现在我可能会 subclass PictureBox 并使其使用不同的ImageAnimator 实施以将 Thread.Sleep() 降低到合理的值。 （ImageAnimator 是一个密封的 class，所以您必须将代码复制到一个新的 class 中，然后在您的 PictureBox 中引用它，而不是为了更流畅的动画。）
原答案：
PictureBox 是一个相当重量级的控件，我建议您使用 Panel 之类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 <100 毫秒的更新间隔会导致它四舍五入为 100 毫秒更新。
相反，您可以自己控制绘画和动画。这使用 PInvoke，因为它使用了一些内核定时器方法。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：我们将定时器调用的 Period 设置为 100000，因为如果将其设置为 0（表示一次性计时），它只会触发一次，即使您随后调用 ChangeTimerQueueTimer.
计时器仍然不适合超精确计时，但这仍然可以为您提供比 PictureBox.
更快的更新速度
我有一个 winforms 应用程序，上面有一个 gif，让用户了解进程停滞。
问题是它的播放速度比在其他应用程序（chrome、Internet Explorer）上看起来慢得多。
我已经在 PictureBox 和 Label 上尝试了 gif，但结果速度是一样的。然后经过一些研究，我遇到了 this 传奇人物@Hans Passant 的问题和答案，但不幸的是，应用他建议的样板代码没有任何区别。
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 的播放速度相同，但低于实际 gif。应用此代码时还有其他需要注意的地方吗？
你只能猜测，我怀疑任何人都不会很幸运地得到一个重现：
- 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，请验证它 returns 0。
- 如果图片很大，那么更新速度可能不够快。或者您的 UI 线程被其他任务占用了太多。 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。每次更新帧时都会进行转换。这是相当昂贵的，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 线程未消耗 100% 核心。
- 您可以通过提升的命令提示符 运行
powercfg /energy获得关于有效计时器周期的第二个意见。在您的应用 运行 时执行此操作。它会滚动一分钟，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发出请求。
更新2021-04-02
PictureBox 以低帧率设置动画背后的根本原因是因为它在幕后使用了 ImageAnimator class，它仅以 20 FPS 设置动画。它在此处的工作线程方法中有一个硬编码的 50 毫秒 Thread.Sleep()：
https://referencesource.microsoft.com/#System.Drawing/commonui/System/Drawing/ImageAnimator.cs,333
最初在编写以下内容时我无法访问 Windows 表单源，但现在我可能会 subclass PictureBox 并使其使用不同的ImageAnimator 实施以将 Thread.Sleep() 降低到合理的值。 （ImageAnimator 是一个密封的 class，所以您必须将代码复制到一个新的 class 中，然后在您的 PictureBox 中引用它，而不是为了更流畅的动画。）
原答案：
PictureBox 是一个相当重量级的控件，我建议您使用 Panel 之类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 <100 毫秒的更新间隔会导致它四舍五入为 100 毫秒更新。
相反，您可以自己控制绘画和动画。这使用 PInvoke，因为它使用了一些内核定时器方法。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：我们将定时器调用的 Period 设置为 100000，因为如果将其设置为 0（表示一次性计时），它只会触发一次，即使您随后调用 ChangeTimerQueueTimer.
计时器仍然不适合超精确计时，但这仍然可以为您提供比 PictureBox.