compress textures on import to platform-specific default format

Editor/Scripts/GLTFImporter.cs

@@ -588,6 +588,17 @@ string GetUniqueName(string desiredName)
 		                        ctx.AddObjectToAsset(GetUniqueName(tex.name), tex);
 		                        if (invalidTextures.Contains(tex))
 			                        tex.hideFlags = HideFlags.HideInHierarchy | HideFlags.HideInInspector;
+
+		                        // platform-dependant texture compression
+		                        var buildTargetName = BuildPipeline.GetBuildTargetName(ctx.selectedBuildTarget);
+		                        var format = TextureImporterHelper.GetAutomaticFormat(tex, buildTargetName);
+		                        var convertedFormat = (TextureFormat) (int) format;
+		                        if ((int) convertedFormat > -1)
+		                        {
+			                        // Debug.Log("Compressing texture " + tex.name + "(format: " + tex.format + ", mips: " + tex.mipmapCount + ") to: " + convertedFormat);
+			                        EditorUtility.CompressTexture(tex, convertedFormat, TextureCompressionQuality.Best);
+			                        // Debug.Log("Mips now: " + tex.mipmapCount); // TODO figure out why mipmaps disappear here
+		                        }
 	                        }
                         }
                     }

Editor/Scripts/Internal/TextureImporterHelper.cs

@@ -0,0 +1,51 @@
+using System;
+using System.Reflection;
+using UnityEditor;
+using UnityEditor.Build;
+using UnityEngine;
+
+namespace UnityGLTF
+{
+    public class TextureImporterHelper
+    {
+        private static MethodInfo GetFixedPlatformName;
+        private const string DefaultTextureAssetGuid = "7b7ff3cec11c24c599d6f12443877d5e";
+
+        public static TextureImporterFormat GetAutomaticFormat(Texture2D texture, string platform)
+        {
+            var defaultTextureImporter = AssetImporter.GetAtPath(AssetDatabase.GUIDToAssetPath(DefaultTextureAssetGuid)) as TextureImporter;
+            // defaultTextureImporter = new TextureImporter();
+
+            if (GetFixedPlatformName == null)
+                GetFixedPlatformName = typeof(TextureImporter)
+                    .GetMethod("GetFixedPlatformName", BindingFlags.Static | BindingFlags.NonPublic);
+
+            if (GetFixedPlatformName == null)
+                throw new MissingMethodException("TextureImporter.GetFixedPlatformName");
+
+            platform = GetFixedPlatformName.Invoke(null, new object[] { platform }) as string;
+            TextureImporterSettings importerSettings = new TextureImporterSettings();
+
+            importerSettings.aniso = 5;
+            importerSettings.wrapMode = texture.wrapMode;
+            importerSettings.filterMode = texture.filterMode;
+            importerSettings.mipmapEnabled = texture.mipmapCount > 1;
+            importerSettings.alphaSource = TextureImporterAlphaSource.FromInput;
+
+            var hasAlpha = TextureUtil.HasAlphaTextureFormat(texture.format);
+            var isHDR = TextureUtil.IsHDRFormat(texture.format);
+
+            // var platformSettings = new TextureImporterPlatformSettings();
+
+            foreach (BuildPlatform validPlatform in BuildPlatforms.instance.GetValidPlatforms())
+            {
+                // TextureImporter.RecommendedFormatsFromTextureTypeAndPlatform
+                if (validPlatform.name == platform)
+                    return TextureImporter.DefaultFormatFromTextureParameters(importerSettings, defaultTextureImporter.GetPlatformTextureSettings(platform), hasAlpha, isHDR, validPlatform.defaultTarget);
+            }
+
+            // This should never happen
+            return TextureImporterFormat.Automatic;
+        }
+    }
+}