CustomFontHelper.cs

using System;
using System.IO;
using System.Linq;
using UnityEditor;
using UnityEngine;

namespace .Editor
{
    public static class CustomFontHelper
    {
        [MenuItem("Assets/CreateCustomFont", true)]
        static bool Validator()
        {
            return Selection.objects.All(x =>
            {
                if (!(x is Texture2D)) return false;

                var importer = TextureImporter.GetAtPath(AssetDatabase.GetAssetPath(x)) as TextureImporter;
                return importer.textureType == TextureImporterType.Sprite &&
                       importer.spriteImportMode == SpriteImportMode.Multiple;
            });
        }

        [MenuItem("Assets/CreateCustomFont")]
        static void CreateCustomFont()
        {
            foreach (string guid in Selection.assetGUIDs)
            {
                string path = AssetDatabase.GUIDToAssetPath(guid);
                var importer = TextureImporter.GetAtPath(path) as TextureImporter;

                var group = importer.spritesheet
                    .OrderBy(x => x.name)
                    .GroupBy(x => x.name.Split('_')[0]);

                Texture2D tex = AssetDatabase.LoadAssetAtPath<Texture2D>(path);
                foreach (var item in group)
                {
                    string savePath = Path.Combine(Path.GetDirectoryName(path), $"{item.Key}.fontsettings");
                    CreateFont(savePath, tex, item.ToArray());
                }
            }

            AssetDatabase.SaveAssets();
            AssetDatabase.Refresh();
        }

        static void CreateFont(string savePath, Texture2D tex, params SpriteMetaData[] spriteMetaDatas)
        {
            int asciiStartOffset = Convert.ToChar(spriteMetaDatas[0].name.Split('_')[1]);
            var font = new Font();
            using (var fontSo = new SerializedObject(font))
            {
                using (var matSp = fontSo.FindProperty("m_DefaultMaterial"))
                {
                    var mat = new Material(Canvas.GetDefaultCanvasMaterial().shader) {mainTexture = tex};
                    string matPath = Path.Combine(Path.GetDirectoryName(savePath),
                        $"{Path.GetFileNameWithoutExtension(savePath)}.mat");
                    AssetDatabase.CreateAsset(mat, matPath);
                    matSp.objectReferenceValue = mat;
                }

                using (var offsetSp = fontSo.FindProperty("m_AsciiStartOffset"))
                {
                    offsetSp.intValue = asciiStartOffset;
                }

                SerializedProperty characterRects = fontSo.FindProperty("m_CharacterRects");
                for (int i = 0; i < spriteMetaDatas.Length; i++)
                {
                    SpriteMetaData metaData = spriteMetaDatas[i];
                    int index = characterRects.arraySize;
                    characterRects.InsertArrayElementAtIndex(index);
                    SerializedProperty item = characterRects.GetArrayElementAtIndex(index);

                    using (var indexSp = item.FindPropertyRelative("index"))
                    {
                        indexSp.intValue = i;
                    }

                    using (var uvSp = item.FindPropertyRelative("uv"))
                    {
                        float x = metaData.rect.x / tex.width;
                        float y = metaData.rect.y / tex.height;
                        float w = metaData.rect.width / tex.width;
                        float h = metaData.rect.height / tex.height;
                        uvSp.rectValue = new Rect(x, y, w, h);
                    }

                    using (var vertSp = item.FindPropertyRelative("vert"))
                    {
                        vertSp.rectValue = new Rect(0, 0, metaData.rect.width, -metaData.rect.height);
                    }

                    using (var advanceSp = item.FindPropertyRelative("advance"))
                    {
                        advanceSp.floatValue = metaData.rect.width;
                    }
                }

                fontSo.ApplyModifiedPropertiesWithoutUndo();
            }

            AssetDatabase.CreateAsset(font, savePath);
        }
    }
}