Spritesheet Slicer

using System.Collections.Generic;
using System.IO;
using UnityEditor;
using UnityEditorInternal;
using UnityEngine;

namespace ManaSeed.Editor
{
    public class SpritesheetSlicer
    {
        public static Vector2 ManaSeedCharacterPivot = new Vector2(0.5f, 0.3125f);

        [MenuItem("Mana Seed/Slice Character Sprites %&s")]
        public static void SliceManaSeedCharacters()
        {
            var textures = Selection.GetFiltered<Texture2D>(SelectionMode.Assets);

            foreach (var texture in textures)
                ProcessManaSeedCharacterTexture(texture);

            Debug.Log("Slicing operation completed.");
        }

        private static void ProcessManaSeedCharacterTexture(Texture2D texture)
        {
            string path = AssetDatabase.GetAssetPath(texture);
            var importer = AssetImporter.GetAtPath(path) as TextureImporter;

            importer.textureType = TextureImporterType.Sprite;
            importer.spriteImportMode = SpriteImportMode.Multiple;
            importer.mipmapEnabled = false;
            importer.spritePivot = ManaSeedCharacterPivot;

            var textureSettings = new TextureImporterSettings();
            importer.ReadTextureSettings(textureSettings);
            textureSettings.spriteMeshType = SpriteMeshType.Tight;
            textureSettings.spriteExtrude = 0;
            importer.SetTextureSettings(textureSettings);

            EditorUtility.SetDirty(importer);

            Rect[] rects = InternalSpriteUtility.GenerateGridSpriteRectangles(texture, Vector2.zero, new Vector2(64, 64), Vector2.zero, true);
            var rectsList = new List<Rect>(rects);
            rectsList = SortRects(rectsList, texture.width);

            string filenameNoExtension = Path.GetFileNameWithoutExtension(path);
            var metas = new List<SpriteMetaData>();
            int rectNum = 0;

            foreach (Rect rect in rectsList)
            {
                var meta = new SpriteMetaData();
                meta.pivot = ManaSeedCharacterPivot;
                meta.alignment = (int)SpriteAlignment.Custom;
                meta.rect = rect;
                meta.name = filenameNoExtension + "_" + rectNum++;
                metas.Add(meta);
            }

            importer.spritesheet = metas.ToArray();

            AssetDatabase.ImportAsset(path, ImportAssetOptions.ForceUpdate);

            Debug.Log("Slicing spritesheet " + texture.name + " completed.");
        }

        private static List<Rect> SortRects(List<Rect> rects, float textureWidth)
        {
            List<Rect> list = new List<Rect>();
            while (rects.Count > 0)
            {
                Rect rect = rects[rects.Count - 1];
                Rect sweepRect = new Rect(0f, rect.yMin, textureWidth, rect.height);
                List<Rect> list2 = RectSweep(rects, sweepRect);
                if (list2.Count <= 0)
                {
                    list.AddRange(rects);
                    break;
                }
                list.AddRange(list2);
            }
            return list;
        }

        private static List<Rect> RectSweep(List<Rect> rects, Rect sweepRect)
        {
            List<Rect> result;
            if (rects == null || rects.Count == 0)
            {
                result = new List<Rect>();
            }
            else
            {
                List<Rect> list = new List<Rect>();
                foreach (Rect current in rects)
                {
                    if (current.Overlaps(sweepRect))
                    {
                        list.Add(current);
                    }
                }
                foreach (Rect current2 in list)
                {
                    rects.Remove(current2);
                }
                list.Sort((a, b) => a.x.CompareTo(b.x));
                result = list;
            }
            return result;
        }
    }
}