The helper class to expose some *REQUIRED* non-public members in the UnityEditor.U2D.PSD.PSDImporter. Such as TextureImporterSettings(Readable), TextureImporterPlatformSettings, "Character Rig", and "Use Layer Grouping".

PSDImporterHelper.cs

/*
* The PSDImporterHelper is to expose some IMPORTANT non-public members in PSDImporter.
* Such as TextureImporterSettings(Readable), TextureImporterPlatformSettings, "Character Rig", and "Use Layer Grouping".
* Created by PeDev 2020 https://gist.github.com/qwe321qwe321qwe321/74ed2c0e8722b0b88c84ddb402d253e6
*/
#if UNITY_EDITOR
#define INCLUDE_PSD_IMPORTER // <---- Comment/Uncomment by yourself.
using System.Collections;
using System.Collections.Generic;
using UnityEditor;
#if INCLUDE_PSD_IMPORTER
using UnityEditor.U2D.PSD;
#endif
using System.Reflection;
namespace Pedev {
#if INCLUDE_PSD_IMPORTER
	/// <summary>
	/// The helper class to expose some *REQUIRED* non-public members in PSDImporter.
	/// </summary>
    public static class PSDImporterHelper {
		private static FieldInfo s_TextureImporterSettingsField = typeof(PSDImporter).GetField("m_TextureImporterSettings", System.Reflection.BindingFlags.NonPublic | System.Reflection.BindingFlags.Instance);
		private static FieldInfo s_CharacterModeField = typeof(PSDImporter).GetField("m_CharacterMode", System.Reflection.BindingFlags.NonPublic | System.Reflection.BindingFlags.Instance);
		private static FieldInfo s_GenerateGOHierarchyField = typeof(PSDImporter).GetField("m_GenerateGOHierarchy", System.Reflection.BindingFlags.NonPublic | System.Reflection.BindingFlags.Instance);
		private static FieldInfo s_PlatformSettingsField = typeof(PSDImporter).GetField("m_PlatformSettings", System.Reflection.BindingFlags.NonPublic | BindingFlags.Instance);
		private static PropertyInfo s_TextureActualWidthProp = typeof(PSDImporter).GetProperty("textureActualWidth", System.Reflection.BindingFlags.NonPublic | System.Reflection.BindingFlags.Instance);
		private static PropertyInfo s_TextureActualHeightProp = typeof(PSDImporter).GetProperty("textureActualHeight", System.Reflection.BindingFlags.NonPublic | System.Reflection.BindingFlags.Instance);

		/// <summary>
		/// Set "Enable Read/Write" in Editor.
		/// </summary>
		/// <param name="importer"></param>
		/// <param name="readable"></param>
		public static void SetReadable(this PSDImporter importer, bool readable) {
			TextureImporterSettings importerSettings = s_TextureImporterSettingsField.GetValue(importer) as TextureImporterSettings;
			importerSettings.readable = readable;
			EditorUtility.SetDirty(importer);
		}

		/// <summary>
		/// Get "Enable Read/Write" in Editor.
		/// </summary>
		/// <param name="importer"></param>
		/// <returns></returns>
		public static bool GetReadable(this PSDImporter importer) {
			TextureImporterSettings importerSettings = s_TextureImporterSettingsField.GetValue(importer) as TextureImporterSettings;
			return importerSettings.readable;
		}

		/// <summary>
		/// Get "Pixel Per Unit" in Editor.
		/// </summary>
		/// <param name="importer"></param>
		/// <returns></returns>
		public static float GetPixelsPerUnit(this PSDImporter importer) {
			TextureImporterSettings importerSettings = s_TextureImporterSettingsField.GetValue(importer) as TextureImporterSettings;
			return importerSettings.spritePixelsPerUnit;
		}

		/// <summary>
		/// Get "Sprite Mesh Type" in Editor.
		/// </summary>
		/// <param name="importer"></param>
		/// <returns></returns>
		public static UnityEngine.SpriteMeshType GetSpriteMeshType(this PSDImporter importer) {
			TextureImporterSettings importerSettings = s_TextureImporterSettingsField.GetValue(importer) as TextureImporterSettings;
			return importerSettings.spriteMeshType;
		}

		/// <summary>
		/// Get "Extrude Edges" in Editor
		/// </summary>
		/// <param name="importer"></param>
		/// <returns></returns>
		public static uint GetSpriteExtrude(this PSDImporter importer) {
			TextureImporterSettings importerSettings = s_TextureImporterSettingsField.GetValue(importer) as TextureImporterSettings;
			return importerSettings.spriteExtrude;
		}

		/// <summary>
		/// Get TextureImporterSettings.
		/// </summary>
		/// <param name="originImporter"></param>
		/// <returns></returns>
		public static TextureImporterSettings GetImporterSettings(this PSDImporter originImporter) {
			TextureImporterSettings importerSettings = s_TextureImporterSettingsField.GetValue(originImporter) as TextureImporterSettings;
			return importerSettings;
		}

		/// <summary>
		/// Get TextureImporterPlatformSettings by private method.
		/// </summary>
		/// <param name="importer"></param>
		/// <returns></returns>
		public static List<TextureImporterPlatformSettings> GetTextureImporterPlatformSettings(this PSDImporter importer) {
			return s_PlatformSettingsField.GetValue(importer) as List<TextureImporterPlatformSettings>;
		}

		/// <summary>
		/// Get textureActualWidth and textureActualHeight.
		/// </summary>
		/// <param name="importer"></param>
		/// <param name="width"></param>
		/// <param name="height"></param>
		public static void GetTextureActualSize(this PSDImporter importer, out int width, out int height) {
			width = (int)s_TextureActualWidthProp.GetValue(importer);
			height = (int)s_TextureActualHeightProp.GetValue(importer);
		}

		/// <summary>
		/// Get the PSDImporter.characterMode value which is "Character Rig" in Editor.
		/// </summary>
		/// <param name="importer"></param>
		/// <param name="value"></param>
		public static bool GetCharacterMode(this PSDImporter importer) {
			bool characterMode = (bool)s_CharacterModeField.GetValue(importer);
			return characterMode;
		}

		/// <summary>
		/// Set the PSDImporter.characterMode value which is "Character Rig" in Editor.
		/// </summary>
		/// <param name="importer"></param>
		/// <param name="value"></param>
		public static void SetCharacterMode(this PSDImporter importer, bool value) {
			s_CharacterModeField.SetValue(importer, value);
		}

		/// <summary>
		/// Get the PSDImporter.m_GenerateGOHierarchy value which is "Use Layer Grouping" in Editor.
		/// </summary>
		/// <param name="importer"></param>
		/// <param name="value"></param>
		public static bool GetGenerateGOHierarchy(this PSDImporter importer) {
			bool generateGOHierarchy = (bool)s_GenerateGOHierarchyField.GetValue(importer);
			return generateGOHierarchy;
		}

		/// <summary>
		/// Set the PSDImporter.m_GenerateGOHierarchy value which is "Use Layer Grouping" in Editor.
		/// </summary>
		/// <param name="importer"></param>
		/// <param name="value"></param>
		public static void SetGenerateGOHierarchy(this PSDImporter importer, bool value) {
			s_GenerateGOHierarchyField.SetValue(importer, value);
		}
	}
#endif
}
#endif