public static (Image <Rgba32>, DeviceBuffer[]) CreateSpriteAtlas(
SpriteFile spriteFile, GraphicsDevice gd, ResourceFactory disposeFactory, TextureLoader textureLoader)
{
//Merge all of the sprite frames together into one texture
//The sprite's bounds are the maximum size that a frame can be
//Since most sprites have identical frame sizes, this lets us optimize pretty well
//Determine how many frames to put on one line
//This helps optimize texture size
var framesPerLine = (int)Math.Ceiling(Math.Sqrt(spriteFile.Frames.Count));
//Account for the change in size when converting textures
(var maximumWith, var maximumHeight) = textureLoader.ComputeScaledSize(spriteFile.MaximumWidth, spriteFile.MaximumHeight);
var totalWidth = maximumWith * framesPerLine;
var totalHeight = maximumHeight * framesPerLine;
var atlasImage = new Image <Rgba32>(totalWidth, totalHeight);
var graphicsOptions = GraphicsOptions.Default;
graphicsOptions.BlenderMode = PixelBlenderMode.Src;
var nextFramePosition = new Point();
//Determine which texture format it is
TextureFormat textureFormat;
switch (spriteFile.TextureFormat)
{
case SpriteTextureFormat.Normal:
case SpriteTextureFormat.Additive:
textureFormat = TextureFormat.Normal;
break;
case SpriteTextureFormat.AlphaTest:
textureFormat = TextureFormat.AlphaTest;
break;
default:
textureFormat = TextureFormat.IndexAlpha;
break;
}
var vertexBuffers = new List <DeviceBuffer>();
foreach (var frame in spriteFile.Frames)
{
//Each individual texture is converted before being added to the atlas to avoid bleeding effects between frames
var frameImage = textureLoader.ConvertTexture(
new IndexedColor256Image(spriteFile.Palette, frame.TextureData, frame.Area.Width, frame.Area.Height),
textureFormat);
atlasImage.Mutate(context => context.DrawImage(graphicsOptions, frameImage, nextFramePosition));
//Note: The frame origin does not apply to texture coordinates, only to vertex offsets
//Important! these are float types
PointF frameOrigin = nextFramePosition;
var frameSize = new SizeF(frameImage.Width, frameImage.Height);
//Convert to texture coordinates
frameOrigin.X /= totalWidth;
frameOrigin.Y /= totalHeight;
frameSize.Width /= totalWidth;
frameSize.Height /= totalHeight;
//The vertices should be scaled to match the frame size
//These don't need to be modified to account for texture scale!
var scale = new Vector3(0, frame.Area.Width, frame.Area.Height);
var translation = new Vector3(0, frame.Area.X, frame.Area.Y);
//Construct the vertices
var vertices = new WorldTextureCoordinate[]
{
new WorldTextureCoordinate
{
Vertex = (Vertices[0] * scale) + translation,
Texture = new Vector2(frameOrigin.X, frameOrigin.Y)
},
new WorldTextureCoordinate
{
Vertex = (Vertices[1] * scale) + translation,
Texture = new Vector2(frameOrigin.X + frameSize.Width, frameOrigin.Y)
},
new WorldTextureCoordinate
{
Vertex = (Vertices[2] * scale) + translation,
Texture = new Vector2(frameOrigin.X + frameSize.Width, frameOrigin.Y + frameSize.Height)
}
,
new WorldTextureCoordinate
{
Vertex = (Vertices[3] * scale) + translation,
Texture = new Vector2(frameOrigin.X, frameOrigin.Y + frameSize.Height)
}
};
var vb = disposeFactory.CreateBuffer(new BufferDescription(vertices.SizeInBytes(), BufferUsage.VertexBuffer));
gd.UpdateBuffer(vb, 0, vertices);
//TODO: could refactor this by having one vertex and one index buffer, and returning the start & count of indices for each frame
vertexBuffers.Add(vb);
nextFramePosition.X += maximumWith;
//Wrap to next line
if (nextFramePosition.X >= totalWidth)
{
nextFramePosition.X = 0;
nextFramePosition.Y += maximumHeight;
}
}
return(atlasImage, vertexBuffers.ToArray());
}
