Misaki.HighPerformance/Misaki.HighPerformance.Image/AnimatedGifEnumerator.cs

using Misaki.HighPerformance.Image.Runtime;
using System;
using System.Collections;
using System.Collections.Generic;
using System.IO;

namespace Misaki.HighPerformance.Image;

internal class AnimatedGifEnumerator : IEnumerator<AnimatedFrameResult>
{
    private readonly StbImage.stbi__context _context;
    private StbImage.stbi__gif _gif;
    private readonly ColorComponents _colorComponents;

    public AnimatedGifEnumerator(Stream input, ColorComponents colorComponents)
    {
        if (input == null)
            throw new ArgumentNullException("input");

        _context = new StbImage.stbi__context(input);

        if (StbImage.stbi__gif_test(_context) == 0)
            throw new Exception("Input stream is not GIF file.");

        _gif = new StbImage.stbi__gif();
        _colorComponents = colorComponents;
    }

    public ColorComponents ColorComponents
    {
        get
        {
            return _colorComponents;
        }
    }

    public AnimatedFrameResult Current
    {
        get; private set;
    }

    object IEnumerator.Current
    {
        get
        {
            return Current;
        }
    }

    public void Dispose()
    {
        Dispose(true);
        GC.SuppressFinalize(this);
    }

    public unsafe bool MoveNext()
    {
        // Read next frame
        int ccomp;
        byte two_back;
        var result = StbImage.stbi__gif_load_next(_context, _gif, &ccomp, (int)ColorComponents, &two_back);
        if (result == null)
            return false;

        Current ??= new AnimatedFrameResult
        {
            Data = result,
            Width = (uint)_gif.w,
            Height = (uint)_gif.h,
            SourceComp = (ColorComponents)ccomp,
            Comp = ColorComponents == ColorComponents.Default ? (ColorComponents)ccomp : ColorComponents
        };

        Current.DelayInMs = _gif.delay;

        return true;
    }

    public void Reset()
    {
        throw new NotImplementedException();
    }

    ~AnimatedGifEnumerator()
    {
        Dispose(false);
    }

    protected virtual unsafe void Dispose(bool disposing)
    {
        if (_gif != null)
        {
            if (_gif._out_ != null)
            {
                CRuntime.free(_gif._out_);
                _gif._out_ = null;
            }

            if (_gif.history != null)
            {
                CRuntime.free(_gif.history);
                _gif.history = null;
            }

            if (_gif.background != null)
            {
                CRuntime.free(_gif.background);
                _gif.background = null;
            }

            _gif = null;
        }
    }
}

internal class AnimatedGifEnumerable : IEnumerable<AnimatedFrameResult>
{
    private readonly Stream _input;
    private readonly ColorComponents _colorComponents;

    public AnimatedGifEnumerable(Stream input, ColorComponents colorComponents)
    {
        _input = input;
        _colorComponents = colorComponents;
    }

    public ColorComponents ColorComponents
    {
        get
        {
            return _colorComponents;
        }
    }

    public IEnumerator<AnimatedFrameResult> GetEnumerator()
    {
        return new AnimatedGifEnumerator(_input, ColorComponents);
    }

    IEnumerator IEnumerable.GetEnumerator()
    {
        return GetEnumerator();
    }
}