diff options
Diffstat (limited to 'src/SMAPI/Framework/Content/AssetDataForImage.cs')
| -rw-r--r-- | src/SMAPI/Framework/Content/AssetDataForImage.cs | 41 |
1 files changed, 38 insertions, 3 deletions
diff --git a/src/SMAPI/Framework/Content/AssetDataForImage.cs b/src/SMAPI/Framework/Content/AssetDataForImage.cs index 5c7b87de..f970762a 100644 --- a/src/SMAPI/Framework/Content/AssetDataForImage.cs +++ b/src/SMAPI/Framework/Content/AssetDataForImage.cs @@ -8,6 +8,14 @@ namespace StardewModdingAPI.Framework.Content internal class AssetDataForImage : AssetData<Texture2D>, IAssetDataForImage { /********* + ** Properties + *********/ + /// <summary>The minimum value to consider non-transparent.</summary> + /// <remarks>On Linux/Mac, fully transparent pixels may have an alpha up to 4 for some reason.</remarks> + private const byte MinOpacity = 5; + + + /********* ** Public methods *********/ /// <summary>Construct an instance.</summary> @@ -53,13 +61,40 @@ namespace StardewModdingAPI.Framework.Content // merge data in overlay mode if (patchMode == PatchMode.Overlay) { + // get target data + Color[] targetData = new Color[pixelCount]; + target.GetData(0, targetArea, targetData, 0, pixelCount); + + // merge pixels Color[] newData = new Color[targetArea.Value.Width * targetArea.Value.Height]; target.GetData(0, targetArea, newData, 0, newData.Length); for (int i = 0; i < sourceData.Length; i++) { - Color pixel = sourceData[i]; - if (pixel.A > 4) // not transparent (note: on Linux/Mac, fully transparent pixels may have an alpha up to 4 for some reason) - newData[i] = pixel; + Color above = sourceData[i]; + Color below = targetData[i]; + + // shortcut transparency + if (above.A < AssetDataForImage.MinOpacity) + continue; + if (below.A < AssetDataForImage.MinOpacity) + { + newData[i] = above; + continue; + } + + // merge pixels + // This performs a conventional alpha blend for the pixels, which are already + // premultiplied by the content pipeline. The formula is derived from + // https://blogs.msdn.microsoft.com/shawnhar/2009/11/06/premultiplied-alpha/. + // Note: don't use named arguments here since they're different between + // Linux/Mac and Windows. + float alphaBelow = 1 - (above.A / 255f); + newData[i] = new Color( + (int)(above.R + (below.R * alphaBelow)), // r + (int)(above.G + (below.G * alphaBelow)), // g + (int)(above.B + (below.B * alphaBelow)), // b + Math.Max(above.A, below.A) // a + ); } sourceData = newData; } |