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premultiply alpha when loading PNGs to avoid transparency issues (#257)

This commit is contained in:
Jesse Plamondon-Willard 2017-04-29 19:51:47 -04:00
parent 9b615fadaa
commit 014014ca0f
2 changed files with 112 additions and 59 deletions
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163
src/StardewModdingAPI/Framework/ContentHelper.cs
View File

@ -1,6 +1,7 @@
using System;
using System.IO;
using System.Linq;
using Microsoft.Xna.Framework;
using Microsoft.Xna.Framework.Content;
using Microsoft.Xna.Framework.Graphics;
using StardewValley;
@ -41,7 +42,7 @@ namespace StardewModdingAPI.Framework
this.RelativeContentFolder = this.GetRelativePath(contentManager.FullRootDirectory, modFolderPath);
}
/// <summary>Fetch and cache content from the game content or mod folder (if not already cached), and return it.</summary>
/// <summary>Load content from the game folder or mod folder (if not already cached), and return it. When loading a <c>.png</c> file, this must be called outside the game's draw loop.</summary>
/// <typeparam name="T">The expected data type. The main supported types are <see cref="Texture2D"/> and dictionaries; other types may be supported by the game's content pipeline.</typeparam>
/// <param name="key">The asset key to fetch (if the <paramref name="source"/> is <see cref="ContentSource.GameContent"/>), or the local path to an XNB file relative to the mod folder.</param>
/// <param name="source">Where to search for a matching content asset.</param>
@ -56,53 +57,61 @@ namespace StardewModdingAPI.Framework
throw new ArgumentException("The asset key or local path contains invalid characters.");
// load content
switch (source)
try
{
case ContentSource.GameContent:
return this.LoadFromGameContent<T>(key, key, source);
switch (source)
{
case ContentSource.GameContent:
return this.ContentManager.Load<T>(key);
case ContentSource.ModFolder:
// find content file
FileInfo file = new FileInfo(Path.Combine(this.ModFolderPath, key));
if (!file.Exists && file.Extension == "")
file = new FileInfo(Path.Combine(this.ModFolderPath, key + ".xnb"));
if (!file.Exists)
throw new ContentLoadException($"There is no file at path '{file.FullName}'.");
case ContentSource.ModFolder:
// find content file
FileInfo file = new FileInfo(Path.Combine(this.ModFolderPath, key));
if (!file.Exists && file.Extension == "")
file = new FileInfo(Path.Combine(this.ModFolderPath, key + ".xnb"));
if (!file.Exists)
throw new ContentLoadException($"There is no file at path '{file.FullName}'.");
// get content-relative path
string contentPath = Path.Combine(this.RelativeContentFolder, key);
if (contentPath.EndsWith(".xnb"))
contentPath = contentPath.Substring(0, contentPath.Length - 4);
// get content-relative path
string contentPath = Path.Combine(this.RelativeContentFolder, key);
if (contentPath.EndsWith(".xnb"))
contentPath = contentPath.Substring(0, contentPath.Length - 4);
// load content
switch (file.Extension.ToLower())
{
case ".xnb":
return this.LoadFromGameContent<T>(contentPath, key, source);
// load content
switch (file.Extension.ToLower())
{
case ".xnb":
return this.ContentManager.Load<T>(contentPath);
case ".png":
// validate
if (typeof(T) != typeof(Texture2D))
throw new ContentLoadException($"Can't read file with extension '{file.Extension}' as type '{typeof(T)}'; must be type '{typeof(Texture2D)}'.");
case ".png":
// validate
if (typeof(T) != typeof(Texture2D))
throw new ContentLoadException($"Can't read file with extension '{file.Extension}' as type '{typeof(T)}'; must be type '{typeof(Texture2D)}'.");
// try cache
if (this.ContentManager.IsLoaded(contentPath))
return this.LoadFromGameContent<T>(contentPath, key, source);
// try cache
if (this.ContentManager.IsLoaded(contentPath))
return this.ContentManager.Load<T>(contentPath);
// fetch & cache
using (FileStream stream = File.OpenRead(file.FullName))
{
Texture2D texture = Texture2D.FromStream(Game1.graphics.GraphicsDevice, stream);
this.ContentManager.Inject(contentPath, texture);
return (T)(object)texture;
}
// fetch & cache
using (FileStream stream = File.OpenRead(file.FullName))
{
var texture = Texture2D.FromStream(Game1.graphics.GraphicsDevice, stream);
texture = this.PremultiplyTransparency(texture);
this.ContentManager.Inject(contentPath, texture);
return (T)(object)texture;
}
default:
throw new ContentLoadException($"Unknown file extension '{file.Extension}'; must be '.xnb' or '.png'.");
}
default:
throw new ContentLoadException($"Unknown file extension '{file.Extension}'; must be '.xnb' or '.png'.");
}
default:
throw new NotSupportedException($"Unknown content source '{source}'.");
default:
throw new NotSupportedException($"Unknown content source '{source}'.");
}
}
catch (Exception ex)
{
throw new ContentLoadException($"{this.ModName} failed loading content asset '{key}' from {source}.", ex);
}
}
@ -110,24 +119,6 @@ namespace StardewModdingAPI.Framework
/*********
** Private methods
*********/
/// <summary>Load a content asset through the underlying content manager, and throw a friendly error if it fails.</summary>
/// <typeparam name="T">The expected data type.</typeparam>
/// <param name="assetKey">The content key.</param>
/// <param name="friendlyKey">The friendly content key to show in errors.</param>
/// <param name="source">The content source for use in errors.</param>
/// <exception cref="ContentLoadException">The content couldn't be loaded.</exception>
private T LoadFromGameContent<T>(string assetKey, string friendlyKey, ContentSource source)
{
try
{
return this.ContentManager.Load<T>(assetKey);
}
catch (Exception ex)
{
throw new ContentLoadException($"{this.ModName} failed loading content asset '{friendlyKey}' from {source}.", ex);
}
}
/// <summary>Get a directory path relative to a given root.</summary>
/// <param name="rootPath">The root path from which the path should be relative.</param>
/// <param name="targetPath">The target file path.</param>
@ -143,5 +134,63 @@ namespace StardewModdingAPI.Framework
return Uri.UnescapeDataString(from.MakeRelativeUri(to).ToString())
.Replace(Path.DirectorySeparatorChar == '/' ? '\\' : '/', Path.DirectorySeparatorChar); // use correct separator for platform
}
/// <summary>Premultiply a texture's alpha values to avoid transparency issues in the game. This is only possible if the game isn't currently drawing.</summary>
/// <param name="texture">The texture to premultiply.</param>
/// <returns>Returns a premultiplied texture.</returns>
/// <remarks>Based on <a href="https://gist.github.com/Layoric/6255384">code by Layoric</a>.</remarks>
private Texture2D PremultiplyTransparency(Texture2D texture)
{
if (Game1.graphics.GraphicsDevice.GetRenderTargets().Any()) // TODO: use a more robust check to detect if the game is drawing
throw new NotSupportedException("Can't load a PNG file while the game is drawing to the screen. Make sure you load content outside the draw loop.");
using (RenderTarget2D renderTarget = new RenderTarget2D(Game1.graphics.GraphicsDevice, texture.Width, texture.Height))
using (SpriteBatch spriteBatch = new SpriteBatch(Game1.graphics.GraphicsDevice))
{
//Viewport originalViewport = Game1.graphics.GraphicsDevice.Viewport;
// create blank slate in render target
Game1.graphics.GraphicsDevice.SetRenderTarget(renderTarget);
Game1.graphics.GraphicsDevice.Clear(Color.Black);
// multiply each color by the source alpha, and write just the color values into the final texture
spriteBatch.Begin(SpriteSortMode.Immediate, new BlendState
{
ColorDestinationBlend = Blend.Zero,
ColorWriteChannels = ColorWriteChannels.Red | ColorWriteChannels.Green | ColorWriteChannels.Blue,
AlphaDestinationBlend = Blend.Zero,
AlphaSourceBlend = Blend.SourceAlpha,
ColorSourceBlend = Blend.SourceAlpha
});
spriteBatch.Draw(texture, texture.Bounds, Color.White);
spriteBatch.End();
// copy the alpha values from the source texture into the final one without multiplying them
spriteBatch.Begin(SpriteSortMode.Immediate, new BlendState
{
ColorWriteChannels = ColorWriteChannels.Alpha,
AlphaDestinationBlend = Blend.Zero,
ColorDestinationBlend = Blend.Zero,
AlphaSourceBlend = Blend.One,
ColorSourceBlend = Blend.One
});
spriteBatch.Draw(texture, texture.Bounds, Color.White);
spriteBatch.End();
// release the GPU
Game1.graphics.GraphicsDevice.SetRenderTarget(null);
//Game1.graphics.GraphicsDevice.Viewport = originalViewport;
// store data from render target because the RenderTarget2D is volatile
var data = new Color[texture.Width * texture.Height];
renderTarget.GetData(data);
// unset texture from graphic device and set modified data back to it
Game1.graphics.GraphicsDevice.Textures[0] = null;
texture.SetData(data);
}
return texture;
}
}
}

8
src/StardewModdingAPI/IContentHelper.cs
View File

@ -1,14 +1,18 @@
using Microsoft.Xna.Framework.Graphics;
using System;
using Microsoft.Xna.Framework.Content;
using Microsoft.Xna.Framework.Graphics;
namespace StardewModdingAPI
{
/// <summary>Provides an API for loading content assets.</summary>
public interface IContentHelper
{
/// <summary>Fetch and cache content from the game content or mod folder (if not already cached), and return it.</summary>
/// <summary>Load content from the game folder or mod folder (if not already cached), and return it. When loading a <c>.png</c> file, this must be called outside the game's draw loop.</summary>
/// <typeparam name="T">The expected data type. The main supported types are <see cref="Texture2D"/> and dictionaries; other types may be supported by the game's content pipeline.</typeparam>
/// <param name="key">The asset key to fetch (if the <paramref name="source"/> is <see cref="ContentSource.GameContent"/>), or the local path to an XNB file relative to the mod folder.</param>
/// <param name="source">Where to search for a matching content asset.</param>
/// <exception cref="ArgumentException">The <paramref name="key"/> is empty or contains invalid characters.</exception>
/// <exception cref="ContentLoadException">The content asset couldn't be loaded (e.g. because it doesn't exist).</exception>
T Load<T>(string key, ContentSource source);
}
}