Aseprite MonoGame Pipeline Extension

Aseprite.cs

// Very special thanks to Noel Berry
// A lot of this is borrowed from https://gist.github.com/NoelFB/778d190e5d17f1b86ebf39325346fcc5

using System.Collections.Generic;
using System;
using System.IO;
using System.IO.Compression;
using System.Text;
using System.Linq;
using Microsoft.Xna.Framework;
using Microsoft.Xna.Framework.Content.Pipeline;
using Impulse.Utilities;


namespace ImpulsePipeline.Aseprite
{
    public enum Modes
    {
        Indexed = 1,
        Grayscale = 2,
        RGBA = 3
    }


    public class Aseprite
    {
        public Modes Mode;
        public int Width;
        public int Height;

        public List<AsepriteFrame> Frames;
        public List<AsepriteLayer> Layers;
        public List<AsepriteTag> Tags;
        public List<AsepriteSlice> Slices;


        private enum Chunks
        {
            OldPaletteA = 0x0004,
            OldPaletteB = 0x0011,
            Layer = 0x2004,
            Cel = 0x2005,
            CelExtra = 0x2006,
            Mask = 0x2016,
            Path = 0x2017,
            FrameTags = 0x2018,
            Palette = 0x2019,
            UserData = 0x2020,
            Slice = 0x2022
        }

        private enum CelTypes
        {
            RawCel = 0,
            LinkedCel = 1,
            CompressedImage = 2
        }

        /// <summary>
        /// Parses Aseprite files.
        /// </summary>
        /// <param name="filename">Filename</param>
        /// <param name="logger">Logger</param>
        public Aseprite(string filename, ContentBuildLogger logger)
        {
            Frames = new List<AsepriteFrame>();
            Layers = new List<AsepriteLayer>();
            Tags = new List<AsepriteTag>();
            Slices = new List<AsepriteSlice>();

            using (var stream = File.OpenRead(filename))
            {
                var reader = new BinaryReader(stream);

                // Helpers for translating the Aseprite file format reference
                // See: https://github.com/aseprite/aseprite/blob/master/docs/ase-file-specs.md
                byte BYTE() { return reader.ReadByte(); }
                ushort WORD() { return reader.ReadUInt16(); }
                short SHORT() { return reader.ReadInt16(); }
                uint DWORD() { return reader.ReadUInt32(); }
                long LONG() { return reader.ReadInt32(); }
                string STRING() { return Encoding.UTF8.GetString(BYTES(WORD())); }
                byte[] BYTES(int number) { return reader.ReadBytes(number); }
                void SEEK(int number) { reader.BaseStream.Position += number; }

                int frameCount;

                // Consume header
                {
                    DWORD();

                    // Magic number
                    var magic = WORD();
                    if (magic != 0xA5e0)
                    {
                        throw new Exception("File doesn't appear to be from Aseprite.");
                    }

                    // Basic info
                    frameCount = WORD();
                    Width = WORD();
                    Height = WORD();
                    Mode = (Modes)(WORD() / 8);

                    logger.LogMessage($"Cels are {Width}x{Height}");

                    // Ignore a bunch of stuff
                    DWORD(); // Flags
                    WORD(); // Speed (deprecated)
                    DWORD(); // 0
                    DWORD(); // 0
                    BYTE(); // Palette entry 
                    SEEK(3); // Ignore these bytes
                    WORD(); // Number of colors (0 means 256 for old sprites)
                    BYTE(); // Pixel width
                    BYTE(); // Pixel height
                    SEEK(92); // For Future
                }

                // Some temporary holders
                var colorBuffer = new byte[Width * Height * (int)Mode];
                var palette = new Color[256];

                IUserData lastUserData = null;

                for (int i = 0; i < frameCount; i++)
                {
                    var frame = new AsepriteFrame();
                    Frames.Add(frame);

                    long frameStart;
                    long frameEnd;
                    int chunkCount;

                    // Frame header
                    {
                        frameStart = reader.BaseStream.Position;
                        frameEnd = frameStart + DWORD();
                        WORD(); // Magic number (always 0xF1FA)
                        chunkCount = WORD();
                        frame.Duration = WORD() / 1000f;
                        SEEK(6); // For future (set to zero)
                    }

                    for (int j = 0; j < chunkCount; j++)
                    {
                        long chunkStart;
                        long chunkEnd;
                        Chunks chunkType;

                        // Chunk header
                        {
                            chunkStart = reader.BaseStream.Position;
                            chunkEnd = chunkStart + DWORD();
                            chunkType = (Chunks)WORD();
                        }

                        // Layer
                        if (chunkType == Chunks.Layer)
                        {
                            var layer = new AsepriteLayer();
                            layer.Flag = (AsepriteLayer.Flags)WORD();
                            layer.Type = (AsepriteLayer.Types)WORD();
                            layer.ChildLevel = WORD();
                            WORD(); // width
                            WORD(); // height
                            layer.BlendMode = (AsepriteLayer.BlendModes)WORD();
                            layer.Opacity = BYTE() / 255f;
                            SEEK(3);
                            layer.Name = STRING();

                            lastUserData = layer;
                            Layers.Add(layer);
                        }

                        // Cel
                        else if (chunkType == Chunks.Cel)
                        {
                            var cel = new AsepriteCel();

                            var layerIndex = WORD();
                            cel.Layer = Layers[layerIndex]; // Layer is row (Frame is column)
                            cel.X = SHORT();
                            cel.Y = SHORT();
                            cel.Opacity = BYTE() / 255f;

                            var celType = (CelTypes)WORD();
                            SEEK(7);
                            if (celType == CelTypes.RawCel || celType == CelTypes.CompressedImage)
                            {
                                cel.Width = WORD();
                                cel.Height = WORD();

                                var byteCount = cel.Width * cel.Height * (int)Mode;

                                if (celType == CelTypes.RawCel)
                                {
                                    reader.Read(colorBuffer, 0, byteCount);
                                }
                                else
                                {
                                    SEEK(2);
                                    var deflate = new DeflateStream(reader.BaseStream, CompressionMode.Decompress);
                                    deflate.Read(colorBuffer, 0, byteCount);
                                }

                                cel.Pixels = new Color[cel.Width * cel.Height];
                                ConvertBytesToPixels(colorBuffer, cel.Pixels, palette);
                            }
                            else if (celType == CelTypes.LinkedCel)
                            {
                                var targetFrame = WORD(); // Frame position to link with

                                // Grab the cel from a previous frame
                                var targetCel = Frames[targetFrame].Cels.Where(c => c.Layer == Layers[layerIndex]).First();
                                cel.Width = targetCel.Width;
                                cel.Height = targetCel.Height;
                                cel.Pixels = targetCel.Pixels;
                            }

                            lastUserData = cel;
                            frame.Cels.Add(cel);
                        }

                        // Palette
                        else if (chunkType == Chunks.Palette)
                        {
                            var size = DWORD();
                            var start = DWORD();
                            var end = DWORD();
                            SEEK(8);

                            for (int c = 0; c < (end - start); c++)
                            {
                                var hasName = Calc.IsBitSet(WORD(), 0);
                                palette[start + c] = Color.FromNonPremultiplied(BYTE(), BYTE(), BYTE(), BYTE());
                                if (hasName)
                                {
                                    STRING(); // Color name
                                }
                            }
                        }

                        // User data
                        else if (chunkType == Chunks.UserData)
                        {
                            if (lastUserData != null)
                            {
                                var flags = DWORD();

                                if (Calc.IsBitSet(flags, 0))
                                {
                                    lastUserData.UserDataText = STRING();
                                }
                                else if (Calc.IsBitSet(flags, 1))
                                {
                                    lastUserData.UserDataColor = Color.FromNonPremultiplied(BYTE(), BYTE(), BYTE(), BYTE());
                                }
                            }
                        }

                        // Tag (animation reference)
                        else if (chunkType == Chunks.FrameTags)
                        {
                            var tagsCount = WORD();
                            SEEK(8);

                            for (int t = 0; t < tagsCount; t++)
                            {
                                var tag = new AsepriteTag();

                                tag.From = WORD();
                                tag.To = WORD();
                                tag.LoopDirection = (AsepriteTag.LoopDirections)BYTE();
                                SEEK(8);
                                tag.Color = Color.FromNonPremultiplied(BYTE(), BYTE(), BYTE(), 255);
                                SEEK(1);
                                tag.Name = STRING();

                                Tags.Add(tag);
                            }
                        }

                        // Slice
                        else if (chunkType == Chunks.Slice)
                        {
                            var slicesCount = DWORD();
                            var flags = DWORD();
                            DWORD();
                            var name = STRING();

                            for (int s = 0; s < slicesCount; s++)
                            {
                                var slice = new AsepriteSlice();
                                slice.Name = name;
                                slice.Frame = (int)DWORD();
                                slice.OriginX = (int)LONG();
                                slice.OriginY = (int)LONG();
                                slice.Width = (int)DWORD();
                                slice.Height = (int)DWORD();

                                // 9 slice
                                if (Calc.IsBitSet(flags, 0))
                                {
                                    LONG(); // Center X position (relative to slice bounds)
                                    LONG(); // Center Y position
                                    DWORD(); // Center width
                                    DWORD(); // Center height
                                }

                                // Pivot
                                else if (Calc.IsBitSet(flags, 1))
                                {
                                    slice.Pivot = new Point((int)DWORD(), (int)DWORD());
                                }

                                lastUserData = slice;
                                Slices.Add(slice);
                            }
                        }

                        reader.BaseStream.Position = chunkEnd;
                    }

                    reader.BaseStream.Position = frameEnd;
                }
            }

            // Log out what we found
            logger.LogMessage("Layers:");
            foreach (var layer in Layers)
            {
                logger.LogMessage($"\t{layer.Name}");
            }
            logger.LogMessage("Animations:");
            foreach (var animation in Tags)
            {
                if (animation.To == animation.From)
                {
                    logger.LogMessage($"\t{animation.Name} => {animation.From + 1}");
                }
                else
                {
                    logger.LogMessage($"\t{animation.Name} => {animation.From + 1} - {animation.To + 1}");
                }
            }
        }


        private void ConvertBytesToPixels(byte[] bytes, Color[] pixels, Color[] palette)
        {
            int length = pixels.Length;

            if (Mode == Modes.RGBA)
            {
                for (int pixel = 0, b = 0; pixel < length; pixel++, b += 4)
                {
                    pixels[pixel].R = (byte)(bytes[b + 0] * bytes[b + 3] / 255);
                    pixels[pixel].G = (byte)(bytes[b + 1] * bytes[b + 3] / 255);
                    pixels[pixel].B = (byte)(bytes[b + 2] * bytes[b + 3] / 255);
                    pixels[pixel].A = bytes[b + 3];
                }
            }
            else if (Mode == Modes.Grayscale)
            {
                for (int pixel = 0, b = 0; pixel < length; pixel++, b += 2)
                {
                    pixels[pixel].R = pixels[pixel].G = pixels[pixel].B = (byte)(bytes[b + 0] * bytes[b + 1] / 255);
                    pixels[pixel].A = bytes[b + 1];
                }
            }
            else if (Mode == Modes.Indexed)
            {
                for (int pixel = 0, paletteIndex = 0; pixel < length; pixel++, paletteIndex += 1)
                {
                    pixels[pixel] = palette[paletteIndex];
                }
            }
        }
    }


    // UserData are extended chunks that get attached
    // to other chunks
    public interface IUserData
    {
        string UserDataText { get; set; }
        Color UserDataColor { get; set; }
    }


    // A layer stores just the meta info for a row
    // of cels
    public class AsepriteLayer : IUserData
    {
        [Flags]
        public enum Flags
        {
            Visible = 1,
            Editable = 2,
            LockMovement = 4,
            Background = 8,
            PreferLinkedCels = 16,
            Collapsed = 32,
            Reference = 64
        }

        public enum Types
        {
            Normal = 0,
            Group = 1
        }

        public enum BlendModes
        {
            Normal = 0,
            Multiply = 1,
            Screen = 2,
            Overlay = 3,
            Darken = 4,
            Lighten = 5,
            ColorDodge = 6,
            ColorBurn = 7,
            HardLight = 8,
            SoftLight = 9,
            Difference = 10,
            Exclusion = 11,
            Hue = 12,
            Saturation = 13,
            Color = 14,
            Luminosity = 15,
            Addition = 16,
            Subtract = 17,
            Divide = 18
        }

        public Flags Flag;
        public Types Type;

        public string Name;
        public float Opacity;
        public BlendModes BlendMode;
        public int ChildLevel;

        string IUserData.UserDataText { get; set; }
        Color IUserData.UserDataColor { get; set; }
    }


    // A frame is a column of cels
    public class AsepriteFrame
    {
        public float Duration;
        public List<AsepriteCel> Cels;


        public AsepriteFrame()
        {
            Cels = new List<AsepriteCel>();
        }
    }


    // Tags are animation references
    public class AsepriteTag
    {
        public enum LoopDirections
        {
            Forward = 0,
            Reverse = 1,
            PingPong = 2
        }

        public string Name;
        public LoopDirections LoopDirection;
        public int From;
        public int To;
        public Color Color;
    }


    public struct AsepriteSlice : IUserData
    {
        public int Frame;
        public string Name;
        public int OriginX;
        public int OriginY;
        public int Width;
        public int Height;
        public Point? Pivot;

        string IUserData.UserDataText { get; set; }
        Color IUserData.UserDataColor { get; set; }
    }


    // Cels are just pixel grids
    public class AsepriteCel : IUserData
    {
        public AsepriteLayer Layer;

        public Color[] Pixels;

        public int X;
        public int Y;
        public int Width;
        public int Height;
        public float Opacity;

        public string UserDataText { get; set; }
        public Color UserDataColor { get; set; }
    }
}

AsepriteImporter.cs

using Microsoft.Xna.Framework.Content.Pipeline;


namespace ImpulsePipeline.Aseprite
{
    [ContentImporter(".aseprite", ".ase", DefaultProcessor = "AsepriteProcessor", DisplayName = "Aseprite Importer - Impulse")]
    public class AsepriteImporter : ContentImporter<Aseprite>
    {
        public override Aseprite Import(string filename, ContentImporterContext context)
        {
            return new Aseprite(filename, context.Logger);
        }
    }
}

AsepriteProcessor.cs

using Microsoft.Xna.Framework.Content.Pipeline;


namespace ImpulsePipeline.Aseprite
{
    [ContentProcessor(DisplayName = "Aseprite Processor - Impulse")]
    public class AsepriteProcessor : ContentProcessor<Aseprite, ProcessedAseprite>
    {
        public override ProcessedAseprite Process(Aseprite input, ContentProcessorContext context)
        {
            return new ProcessedAseprite()
            {
                Logger = context.Logger,
                Aseprite = input
            };
        }
    }


    public class ProcessedAseprite
    {
        public ContentBuildLogger Logger;
        public Aseprite Aseprite;
    }
}

AsepriteReader.cs

using Impulse.Graphics;
using Microsoft.Xna.Framework;
using Microsoft.Xna.Framework.Content;
using Microsoft.Xna.Framework.Graphics;
using System.Collections.Generic;


namespace Impulse.Content
{
    public class AsepriteReader : ContentTypeReader<Aseprite>
    {
        protected override Aseprite Read(ContentReader input, Aseprite existingInstance)
        {
            if (existingInstance != null) return existingInstance;

            int width = input.ReadInt32();
            int height = input.ReadInt32();

            Aseprite aseprite = new Aseprite()
            {
                Width = width,
                Height = height
            };

            // Layers
            int layersCount = input.ReadInt32();
            SpriteLayer layer;
            List<SpriteLayer> layersByIndex = new List<SpriteLayer>();
            for (int i = 0; i < layersCount; i++)
            {
                layer = new SpriteLayer()
                {
                    Name = input.ReadString(),
                    Opacity = input.ReadSingle(),
                    BlendMode = (SpriteLayer.BlendModes)input.ReadInt32(),
                    IsVisible = input.ReadBoolean()
                };
                aseprite.Layers.Add(layer.Name, layer);

                // Use this for referencing cels down further
                layersByIndex.Add(layer);
            }

            // Frames
            int framesCount = input.ReadInt32();
            SpriteFrame frame;
            int celsCount;
            SpriteCel cel;
            int celOriginX;
            int celOriginY;
            int celWidth;
            int celHeight;
            Color pixel;
            int pixelIndex;

            int textureWidth = framesCount * width;
            int textureHeight = layersCount * height;
            Color[] pixelData = new Color[textureWidth * textureHeight];

            for (int f = 0; f < framesCount; f++)
            {
                frame = new SpriteFrame()
                {
                    Duration = input.ReadSingle()
                };

                // Cels
                celsCount = input.ReadInt32();
                for (int i = 0; i < celsCount; i++)
                {
                    int layerIndex = input.ReadInt32();
                    cel = new SpriteCel()
                    {
                        Layer = layersByIndex[layerIndex],
                        ClipRect = new Rectangle(f * width, layerIndex * height, width, height)
                    };
                    frame.Cels.Add(cel);

                    // Get info for the texture
                    celOriginX = input.ReadInt32();
                    celOriginY = input.ReadInt32();
                    celWidth = input.ReadInt32();
                    celHeight = input.ReadInt32();
                    for (int celY = celOriginY; celY < celOriginY + celHeight; celY++)
                    {
                        for (int celX = celOriginX; celX < celOriginX + celWidth; celX++)
                        {
                            pixel = input.ReadColor();
                            //           | x                  | y
                            pixelIndex = (f * width) + celX + ((layerIndex * height) + celY) * textureWidth;
                            pixelData[pixelIndex] = pixel;
                        }
                    }
                }

                aseprite.Frames.Add(frame);
            }

            // Dump our pixels into the texture
            aseprite.Texture = new Texture2D(Engine.Graphics.GraphicsDevice, textureWidth, textureHeight);
            aseprite.Texture.SetData(pixelData);

            // Animations
            int animationsCount = input.ReadInt32();
            SpriteAnimation animation;
            for (int i = 0; i < animationsCount; i++)
            {
                animation = new SpriteAnimation()
                {
                    Name = input.ReadString(),
                    FirstFrame = input.ReadInt32(),
                    LastFrame = input.ReadInt32()
                };
                aseprite.Animations.Add(animation.Name, animation);
            }

            // If no animations were added then just add one 
            // that covers all frames
            if (aseprite.Animations.Count == 0)
            {
                animation = new SpriteAnimation()
                {
                    Name = "Idle",
                    FirstFrame = 0,
                    LastFrame = aseprite.Frames.Count - 1
                };
                aseprite.Animations.Add(animation.Name, animation);
            }

            return aseprite;
        }
    }
}

AsepriteWriter.cs

using System;
using Microsoft.Xna.Framework.Content.Pipeline;
using Microsoft.Xna.Framework.Content.Pipeline.Serialization.Compiler;
using Impulse.Content;


namespace ImpulsePipeline.Aseprite
{
    [ContentTypeWriter]
    class AsepriteWriter : ContentTypeWriter<ProcessedAseprite>
    {
        /// <summary>
        /// Write the Aseprite file. Format is:
        /// 
        ///     Aseprite Document:
        ///         Width
        ///         Height
        ///         Layers: []
        ///             Name
        ///             Opacity
        ///             BlendMode
        ///             IsVisible
        ///         Frames: []
        ///             Duration
        ///             Cels: []
        ///                 LayerIndex
        ///                 X
        ///                 Y
        ///                 Width
        ///                 Height
        ///                 Pixels
        ///         Animations: []
        ///             Name
        ///             From
        ///             To
        /// 
        /// </summary>
        /// <param name="output">Output.</param>
        /// <param name="value">Value.</param>
        protected override void Write(ContentWriter output, ProcessedAseprite value)
        {
            Aseprite aseprite = value.Aseprite;

            output.Write(aseprite.Width);
            output.Write(aseprite.Height);

            // Layers
            output.Write(aseprite.Layers.Count);
            foreach (var layer in aseprite.Layers)
            {
                output.Write(layer.Name);
                output.Write(layer.Opacity);
                output.Write((int)layer.BlendMode);
                output.Write(layer.Flag.HasFlag(AsepriteLayer.Flags.Visible));
            }

            // Frames
            output.Write(aseprite.Frames.Count);
            foreach (var frame in aseprite.Frames)
            {
                output.Write(frame.Duration);
                output.Write(frame.Cels.Count);
                for (int i = 0; i < frame.Cels.Count; i++)
                {
                    var cel = frame.Cels[i];
                    output.Write(aseprite.Layers.IndexOf(cel.Layer));
                    output.Write(cel.X);
                    output.Write(cel.Y);
                    output.Write(cel.Width);
                    output.Write(cel.Height);
                    int size = cel.Width * cel.Height;
                    for (int p = 0; p < size; p++)
                    {
                        output.Write(cel.Pixels[p]);
                    }
                }
            }

            // Animations
            output.Write(aseprite.Tags.Count);
            foreach (var animation in aseprite.Tags)
            {
                output.Write(animation.Name);
                output.Write(animation.From);
                output.Write(animation.To);
            }
        }


        public override string GetRuntimeType(TargetPlatform targetPlatform)
        {
            Type type = typeof(AsepriteReader);
            string readerType = type.Namespace + ".AsepriteReader, " + type.AssemblyQualifiedName;
            return readerType;
        }


        public override string GetRuntimeReader(TargetPlatform targetPlatform)
        {
            Type type = typeof(AsepriteReader);
            string readerType = type.Namespace + ".AsepriteReader, " + type.Assembly.FullName;
            return readerType;
        }
    }
}

See my comment here for anyone having issues with larger files