unity-editor-tools/editor/ImageConverter.cs

using UnityEngine;
using UnityEditor;


namespace editor
{
    public class ImageConverter : EditorWindow
    {
        [MenuItem("Tools/Image Converter Window")]
        public static void ShowWindow()
        {
            GetWindow<ImageConverter>("Image Converter");
        }

        private void OnGUI()
        {
            GUILayout.Label("Image Converter", EditorStyles.boldLabel);
            GUILayout.Space(10);
            GUILayout.Label($"Selected: {Selection.objects.Length}");
            GUILayout.Space(20);
            if (GUILayout.Button("To Sprite"))
            {
                ConvertSelectedTexturesToSprites();
            }
            if (GUILayout.Button("To Default"))
            {
                ConvertSelectedTexturesToSDefault();
            }
        }

        private static void ConvertSelectedTexturesToSprites()
        {   
            int count = 0;
            Debug.Log("Convert selected textures...");
            foreach (Object obj in Selection.objects)
            {
                string path = AssetDatabase.GetAssetPath(obj);
                if (string.IsNullOrEmpty(path))
                    continue;

                TextureImporter textureImporter = AssetImporter.GetAtPath(path) as TextureImporter;
                if (textureImporter == null)
                    continue;

                textureImporter.textureType = TextureImporterType.Sprite;
                textureImporter.spriteImportMode = SpriteImportMode.Single;
                textureImporter.SaveAndReimport();
                count++;
            }
            Debug.Log($"Converted {count} textures.");
        }
        
        private static void ConvertSelectedTexturesToSDefault()
        {   
            int count = 0;
            Debug.Log("Convert selected textures...");
            foreach (Object obj in Selection.objects)
            {
                string path = AssetDatabase.GetAssetPath(obj);
                if (string.IsNullOrEmpty(path))
                    continue;

                TextureImporter textureImporter = AssetImporter.GetAtPath(path) as TextureImporter;
                if (textureImporter == null)
                    continue;

                textureImporter.textureType = TextureImporterType.Default;
                textureImporter.spriteImportMode = SpriteImportMode.Multiple;
                textureImporter.SaveAndReimport();
                count++;
            }
            Debug.Log($"Converted {count} textures.");
        }
    }
}