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c# - 如何在 .net 中创建动画 gif

转载 作者:IT王子 更新时间:2023-10-29 03:49:26 28 4
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有谁知道如何使用 C# 创建动画 gif?理想情况下,我可以控制所使用的颜色还原。

使用 imagemagick(作为外部启动进程)是最佳选择吗?

最佳答案

此 Gif 动画创建器代码来自 https://github.com/DataDink/Bumpkit可以为每个帧设置延迟:

使用 .Net 标准 Gif 编码并添加动画标题。

编辑:使代码类似于典型的文件编写器。

using System;
using System.Drawing;
using System.Drawing.Imaging;
using System.IO;
using System.Threading.Tasks;

/// <summary>
/// Creates a GIF using .Net GIF encoding and additional animation headers.
/// </summary>
public class GifWriter : IDisposable
{
#region Fields
const long SourceGlobalColorInfoPosition = 10,
SourceImageBlockPosition = 789;

readonly BinaryWriter _writer;
bool _firstFrame = true;
readonly object _syncLock = new object();
#endregion

/// <summary>
/// Creates a new instance of GifWriter.
/// </summary>
/// <param name="OutStream">The <see cref="Stream"/> to output the Gif to.</param>
/// <param name="DefaultFrameDelay">Default Delay between consecutive frames... FrameRate = 1000 / DefaultFrameDelay.</param>
/// <param name="Repeat">No of times the Gif should repeat... -1 not to repeat, 0 to repeat indefinitely.</param>
public GifWriter(Stream OutStream, int DefaultFrameDelay = 500, int Repeat = -1)
{
if (OutStream == null)
throw new ArgumentNullException(nameof(OutStream));

if (DefaultFrameDelay <= 0)
throw new ArgumentOutOfRangeException(nameof(DefaultFrameDelay));

if (Repeat < -1)
throw new ArgumentOutOfRangeException(nameof(Repeat));

_writer = new BinaryWriter(OutStream);
this.DefaultFrameDelay = DefaultFrameDelay;
this.Repeat = Repeat;
}

/// <summary>
/// Creates a new instance of GifWriter.
/// </summary>
/// <param name="FileName">The path to the file to output the Gif to.</param>
/// <param name="DefaultFrameDelay">Default Delay between consecutive frames... FrameRate = 1000 / DefaultFrameDelay.</param>
/// <param name="Repeat">No of times the Gif should repeat... -1 not to repeat, 0 to repeat indefinitely.</param>
public GifWriter(string FileName, int DefaultFrameDelay = 500, int Repeat = -1)
: this(new FileStream(FileName, FileMode.OpenOrCreate, FileAccess.Write, FileShare.Read), DefaultFrameDelay, Repeat) { }

#region Properties
/// <summary>
/// Gets or Sets the Default Width of a Frame. Used when unspecified.
/// </summary>
public int DefaultWidth { get; set; }

/// <summary>
/// Gets or Sets the Default Height of a Frame. Used when unspecified.
/// </summary>
public int DefaultHeight { get; set; }

/// <summary>
/// Gets or Sets the Default Delay in Milliseconds.
/// </summary>
public int DefaultFrameDelay { get; set; }

/// <summary>
/// The Number of Times the Animation must repeat.
/// -1 indicates no repeat. 0 indicates repeat indefinitely
/// </summary>
public int Repeat { get; }
#endregion

/// <summary>
/// Adds a frame to this animation.
/// </summary>
/// <param name="Image">The image to add</param>
/// <param name="Delay">Delay in Milliseconds between this and last frame... 0 = <see cref="DefaultFrameDelay"/></param>
public void WriteFrame(Image Image, int Delay = 0)
{
lock (_syncLock)
using (var gifStream = new MemoryStream())
{
Image.Save(gifStream, ImageFormat.Gif);

// Steal the global color table info
if (_firstFrame)
InitHeader(gifStream, _writer, Image.Width, Image.Height);

WriteGraphicControlBlock(gifStream, _writer, Delay == 0 ? DefaultFrameDelay : Delay);
WriteImageBlock(gifStream, _writer, !_firstFrame, 0, 0, Image.Width, Image.Height);
}

if (_firstFrame)
_firstFrame = false;
}

#region Write
void InitHeader(Stream SourceGif, BinaryWriter Writer, int Width, int Height)
{
// File Header
Writer.Write("GIF".ToCharArray()); // File type
Writer.Write("89a".ToCharArray()); // File Version

Writer.Write((short)(DefaultWidth == 0 ? Width : DefaultWidth)); // Initial Logical Width
Writer.Write((short)(DefaultHeight == 0 ? Height : DefaultHeight)); // Initial Logical Height

SourceGif.Position = SourceGlobalColorInfoPosition;
Writer.Write((byte)SourceGif.ReadByte()); // Global Color Table Info
Writer.Write((byte)0); // Background Color Index
Writer.Write((byte)0); // Pixel aspect ratio
WriteColorTable(SourceGif, Writer);

// App Extension Header for Repeating
if (Repeat == -1)
return;

Writer.Write(unchecked((short)0xff21)); // Application Extension Block Identifier
Writer.Write((byte)0x0b); // Application Block Size
Writer.Write("NETSCAPE2.0".ToCharArray()); // Application Identifier
Writer.Write((byte)3); // Application block length
Writer.Write((byte)1);
Writer.Write((short)Repeat); // Repeat count for images.
Writer.Write((byte)0); // terminator
}

static void WriteColorTable(Stream SourceGif, BinaryWriter Writer)
{
SourceGif.Position = 13; // Locating the image color table
var colorTable = new byte[768];
SourceGif.Read(colorTable, 0, colorTable.Length);
Writer.Write(colorTable, 0, colorTable.Length);
}

static void WriteGraphicControlBlock(Stream SourceGif, BinaryWriter Writer, int FrameDelay)
{
SourceGif.Position = 781; // Locating the source GCE
var blockhead = new byte[8];
SourceGif.Read(blockhead, 0, blockhead.Length); // Reading source GCE

Writer.Write(unchecked((short)0xf921)); // Identifier
Writer.Write((byte)0x04); // Block Size
Writer.Write((byte)(blockhead[3] & 0xf7 | 0x08)); // Setting disposal flag
Writer.Write((short)(FrameDelay / 10)); // Setting frame delay
Writer.Write(blockhead[6]); // Transparent color index
Writer.Write((byte)0); // Terminator
}

static void WriteImageBlock(Stream SourceGif, BinaryWriter Writer, bool IncludeColorTable, int X, int Y, int Width, int Height)
{
SourceGif.Position = SourceImageBlockPosition; // Locating the image block
var header = new byte[11];
SourceGif.Read(header, 0, header.Length);
Writer.Write(header[0]); // Separator
Writer.Write((short)X); // Position X
Writer.Write((short)Y); // Position Y
Writer.Write((short)Width); // Width
Writer.Write((short)Height); // Height

if (IncludeColorTable) // If first frame, use global color table - else use local
{
SourceGif.Position = SourceGlobalColorInfoPosition;
Writer.Write((byte)(SourceGif.ReadByte() & 0x3f | 0x80)); // Enabling local color table
WriteColorTable(SourceGif, Writer);
}
else Writer.Write((byte)(header[9] & 0x07 | 0x07)); // Disabling local color table

Writer.Write(header[10]); // LZW Min Code Size

// Read/Write image data
SourceGif.Position = SourceImageBlockPosition + header.Length;

var dataLength = SourceGif.ReadByte();
while (dataLength > 0)
{
var imgData = new byte[dataLength];
SourceGif.Read(imgData, 0, dataLength);

Writer.Write((byte)dataLength);
Writer.Write(imgData, 0, dataLength);
dataLength = SourceGif.ReadByte();
}

Writer.Write((byte)0); // Terminator
}
#endregion

/// <summary>
/// Frees all resources used by this object.
/// </summary>
public void Dispose()
{
// Complete File
_writer.Write((byte)0x3b); // File Trailer

_writer.BaseStream.Dispose();
_writer.Dispose();
}
}

关于c# - 如何在 .net 中创建动画 gif,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/1196322/

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