    ﻿using System;
    using System.Collections.Generic;
    using System.Globalization;
    using System.IO;

    namespace Nikse.SubtitleEdit.Core.SubtitleFormats
    {
        /// <summary>
        /// http://forum.videohelp.com/threads/365786-Converting-Subtitles-%28XML-PNG%29-to-idx-sub
        /// </summary>
        public class SatBoxPng : SubtitleFormat
        {
            public override string Extension => ".txt";

            public override string Name => "SatBox png";

            public override string ToText(Subtitle subtitle, string title)
            {
                return "Not implemented";
            }

            public override void LoadSubtitle(Subtitle subtitle, List<string> lines, string fileName)
            {
                //<I s="0.600" e="3.720" x="268" y="458" w="218" h="58" i="AYZ1.png" />
                Paragraph p = null;
                subtitle.Paragraphs.Clear();
                _errorCount = 0;
                if (string.IsNullOrEmpty(fileName))
                    return;
                string path = Path.GetDirectoryName(fileName);
                foreach (string line in lines)
                {
                    if (line.Contains(" s=\"") && line.Contains(" e=\"") && line.Contains(" i=\"") && line.Contains(".png") && (line.Contains("<I ") || line.Contains("&lt;I ")))
                    {
                        string start = GetTagValue("s", line);
                        string end = GetTagValue("e", line);
                        string text = GetTagValue("i", line);
                        try
                        {
                            if (path != null && File.Exists(Path.Combine(path, text)))
                            {
                                text = Path.Combine(path, text);
                            }
                            else if (path != null)
                            {
                                int indexOfSlash = text.LastIndexOf("/", StringComparison.Ordinal);
                                if (indexOfSlash >= 0 && File.Exists(Path.Combine(path, text.Remove(0, indexOfSlash + 1))))
                                    text = Path.Combine(path, text.Remove(0, indexOfSlash + 1));
                            }
                            p = new Paragraph(DecodeTimeCode(start), DecodeTimeCode(end), text);
                            subtitle.Paragraphs.Add(p);
                        }
                        catch (Exception exception)
                        {
                            _errorCount++;
                            System.Diagnostics.Debug.WriteLine(exception.Message);
                        }
                    }
                    else if (!string.IsNullOrWhiteSpace(line) && p != null)
                    {
                        _errorCount++;
                    }
                }
                subtitle.Renumber();
            }

            private static string GetTagValue(string tag, string line)
            {
                var start = line.IndexOf(tag + "=\"", StringComparison.Ordinal);
                if (start > 0 && line.Length > start + 4)
                {
                    int end = line.IndexOf('"', start + 3);
                    if (end > 0 && line.Length > end + 3)
                    {
                        string value = line.Substring(start + 3, end - start - 3);
                        return value;
                    }
                }
                return string.Empty;
            }

            private static TimeCode DecodeTimeCode(string s)
            {
                return TimeCode.FromSeconds(double.Parse(s, CultureInfo.InvariantCulture));
            }

        }
    }

↑ V3095 The 'line' object was used before it was verified against null. Check lines: 33, 59.