gistfile1.cs

    private void PerformSlice()
    {
        XmlDocument document = new XmlDocument();
        document.LoadXml(xmlAsset.text);

        XmlElement root = document.DocumentElement;
        if (root.Name == "TextureAtlas") {
            bool failed = false;

            Texture2D texture = AssetDatabase.LoadMainAssetAtPath(importer.assetPath) as Texture2D;
            int textureHeight = texture.height;

            List<SpriteMetaData> metaDataList = new List<SpriteMetaData>();

            foreach (XmlNode childNode in root.ChildNodes)
            {
                if (childNode.Name == "SubTexture") {
                    try {
                        int width = Convert.ToInt32(childNode.Attributes["width"].Value);
                        int height = Convert.ToInt32(childNode.Attributes["height"].Value);
                        int x = Convert.ToInt32(childNode.Attributes["x"].Value);
                        int y = textureHeight - (height + Convert.ToInt32(childNode.Attributes["y"].Value));

                        SpriteMetaData spriteMetaData = new SpriteMetaData
                        {
                            alignment = (int)spriteAlignment,
                            border = new Vector4(),
                            name = childNode.Attributes["name"].Value,
                            pivot = GetPivotValue(spriteAlignment, customOffset),
                            rect = new Rect(x, y, width, height)
                        };

                        metaDataList.Add(spriteMetaData);
                    }
                    catch (Exception exception) {
                        failed = true;
                        Debug.LogException(exception);
                    }
                }
                else
                {
                    Debug.LogError("Child nodes should be named 'SubTexture' !");
                    failed = true;
                }
            }

            if (!failed) {
                importer.spriteImportMode = SpriteImportMode.Multiple; 
                importer.spritesheet = metaDataList.ToArray();

                EditorUtility.SetDirty(importer);

                try
                {
                    AssetDatabase.StartAssetEditing();
                    AssetDatabase.ImportAsset(importer.assetPath);
                }
                finally
                {
                    AssetDatabase.StopAssetEditing();
                    Close();
                }
            }
        }
        else
        {
            Debug.LogError("XML needs to have a 'TextureAtlas' root node!");
        }
    }