Program.cs

using System;
using System.IO;
using System.Drawing;

using ICSharpCode.SharpZipLib.Zip.Compression.Streams;

namespace PNGDecoder
{

    public class Decoder
    {
        byte[] data;
        long hash;
        long nextPos;

        public Decoder(byte[] data)
        {
            this.data = data;
            hash = 0x811c9dc5;
            nextPos = 0x0b400;
        }

        public int Decode(byte[] dst)
        {
            for (int j = 0; j < dst.Length; ++j)
            {
                byte b = 0;
                for (int i = 0; i < 8; ++i)
                {
                    var n = nextPos;
                    long d = data[n];
                    var e = (hash * 0x1000193) & 0xffffffff;
                    hash = e ^ ((n & 7) | (d & 0xf8));
                    e = ((d & 1) << 7) ^ ((hash & 0x8000) >> 8);
                    b = (byte) ((b >> 1) | e);
                    nextPos = (n >> 1) ^ (0x0b400 & -(n & 1));

                    if (nextPos == 0x0b400)
                    {
                        return j;
                    }

                }
                dst[j] = b;
            }

            return dst.Length;
        }


    }

    class Program
    {
        private static readonly ulong[] CRC64_Table = {
   0x0000000000000000, 0x42F0E1EBA9EA3693, 0x85E1C3D753D46D26, 0xC711223CFA3E5BB5,
   0x493366450E42ECDF, 0x0BC387AEA7A8DA4C, 0xCCD2A5925D9681F9, 0x8E224479F47CB76A,
   0x9266CC8A1C85D9BE, 0xD0962D61B56FEF2D, 0x17870F5D4F51B498, 0x5577EEB6E6BB820B,
   0xDB55AACF12C73561, 0x99A54B24BB2D03F2, 0x5EB4691841135847, 0x1C4488F3E8F96ED4,
   0x663D78FF90E185EF, 0x24CD9914390BB37C, 0xE3DCBB28C335E8C9, 0xA12C5AC36ADFDE5A,
   0x2F0E1EBA9EA36930, 0x6DFEFF5137495FA3, 0xAAEFDD6DCD770416, 0xE81F3C86649D3285,
   0xF45BB4758C645C51, 0xB6AB559E258E6AC2, 0x71BA77A2DFB03177, 0x334A9649765A07E4,
   0xBD68D2308226B08E, 0xFF9833DB2BCC861D, 0x388911E7D1F2DDA8, 0x7A79F00C7818EB3B,
   0xCC7AF1FF21C30BDE, 0x8E8A101488293D4D, 0x499B3228721766F8, 0x0B6BD3C3DBFD506B,
   0x854997BA2F81E701, 0xC7B97651866BD192, 0x00A8546D7C558A27, 0x4258B586D5BFBCB4,
   0x5E1C3D753D46D260, 0x1CECDC9E94ACE4F3, 0xDBFDFEA26E92BF46, 0x990D1F49C77889D5,
   0x172F5B3033043EBF, 0x55DFBADB9AEE082C, 0x92CE98E760D05399, 0xD03E790CC93A650A,
   0xAA478900B1228E31, 0xE8B768EB18C8B8A2, 0x2FA64AD7E2F6E317, 0x6D56AB3C4B1CD584,
   0xE374EF45BF6062EE, 0xA1840EAE168A547D, 0x66952C92ECB40FC8, 0x2465CD79455E395B,
   0x3821458AADA7578F, 0x7AD1A461044D611C, 0xBDC0865DFE733AA9, 0xFF3067B657990C3A,
   0x711223CFA3E5BB50, 0x33E2C2240A0F8DC3, 0xF4F3E018F031D676, 0xB60301F359DBE0E5,
   0xDA050215EA6C212F, 0x98F5E3FE438617BC, 0x5FE4C1C2B9B84C09, 0x1D14202910527A9A,
   0x93366450E42ECDF0, 0xD1C685BB4DC4FB63, 0x16D7A787B7FAA0D6, 0x5427466C1E109645,
   0x4863CE9FF6E9F891, 0x0A932F745F03CE02, 0xCD820D48A53D95B7, 0x8F72ECA30CD7A324,
   0x0150A8DAF8AB144E, 0x43A04931514122DD, 0x84B16B0DAB7F7968, 0xC6418AE602954FFB,
   0xBC387AEA7A8DA4C0, 0xFEC89B01D3679253, 0x39D9B93D2959C9E6, 0x7B2958D680B3FF75,
   0xF50B1CAF74CF481F, 0xB7FBFD44DD257E8C, 0x70EADF78271B2539, 0x321A3E938EF113AA,
   0x2E5EB66066087D7E, 0x6CAE578BCFE24BED, 0xABBF75B735DC1058, 0xE94F945C9C3626CB,
   0x676DD025684A91A1, 0x259D31CEC1A0A732, 0xE28C13F23B9EFC87, 0xA07CF2199274CA14,
   0x167FF3EACBAF2AF1, 0x548F120162451C62, 0x939E303D987B47D7, 0xD16ED1D631917144,
   0x5F4C95AFC5EDC62E, 0x1DBC74446C07F0BD, 0xDAAD56789639AB08, 0x985DB7933FD39D9B,
   0x84193F60D72AF34F, 0xC6E9DE8B7EC0C5DC, 0x01F8FCB784FE9E69, 0x43081D5C2D14A8FA,
   0xCD2A5925D9681F90, 0x8FDAB8CE70822903, 0x48CB9AF28ABC72B6, 0x0A3B7B1923564425,
   0x70428B155B4EAF1E, 0x32B26AFEF2A4998D, 0xF5A348C2089AC238, 0xB753A929A170F4AB,
   0x3971ED50550C43C1, 0x7B810CBBFCE67552, 0xBC902E8706D82EE7, 0xFE60CF6CAF321874,
   0xE224479F47CB76A0, 0xA0D4A674EE214033, 0x67C58448141F1B86, 0x253565A3BDF52D15,
   0xAB1721DA49899A7F, 0xE9E7C031E063ACEC, 0x2EF6E20D1A5DF759, 0x6C0603E6B3B7C1CA,
   0xF6FAE5C07D3274CD, 0xB40A042BD4D8425E, 0x731B26172EE619EB, 0x31EBC7FC870C2F78,
   0xBFC9838573709812, 0xFD39626EDA9AAE81, 0x3A28405220A4F534, 0x78D8A1B9894EC3A7,
   0x649C294A61B7AD73, 0x266CC8A1C85D9BE0, 0xE17DEA9D3263C055, 0xA38D0B769B89F6C6,
   0x2DAF4F0F6FF541AC, 0x6F5FAEE4C61F773F, 0xA84E8CD83C212C8A, 0xEABE6D3395CB1A19,
   0x90C79D3FEDD3F122, 0xD2377CD44439C7B1, 0x15265EE8BE079C04, 0x57D6BF0317EDAA97,
   0xD9F4FB7AE3911DFD, 0x9B041A914A7B2B6E, 0x5C1538ADB04570DB, 0x1EE5D94619AF4648,
   0x02A151B5F156289C, 0x4051B05E58BC1E0F, 0x87409262A28245BA, 0xC5B073890B687329,
   0x4B9237F0FF14C443, 0x0962D61B56FEF2D0, 0xCE73F427ACC0A965, 0x8C8315CC052A9FF6,
   0x3A80143F5CF17F13, 0x7870F5D4F51B4980, 0xBF61D7E80F251235, 0xFD913603A6CF24A6,
   0x73B3727A52B393CC, 0x31439391FB59A55F, 0xF652B1AD0167FEEA, 0xB4A25046A88DC879,
   0xA8E6D8B54074A6AD, 0xEA16395EE99E903E, 0x2D071B6213A0CB8B, 0x6FF7FA89BA4AFD18,
   0xE1D5BEF04E364A72, 0xA3255F1BE7DC7CE1, 0x64347D271DE22754, 0x26C49CCCB40811C7,
   0x5CBD6CC0CC10FAFC, 0x1E4D8D2B65FACC6F, 0xD95CAF179FC497DA, 0x9BAC4EFC362EA149,
   0x158E0A85C2521623, 0x577EEB6E6BB820B0, 0x906FC95291867B05, 0xD29F28B9386C4D96,
   0xCEDBA04AD0952342, 0x8C2B41A1797F15D1, 0x4B3A639D83414E64, 0x09CA82762AAB78F7,
   0x87E8C60FDED7CF9D, 0xC51827E4773DF90E, 0x020905D88D03A2BB, 0x40F9E43324E99428,
   0x2CFFE7D5975E55E2, 0x6E0F063E3EB46371, 0xA91E2402C48A38C4, 0xEBEEC5E96D600E57,
   0x65CC8190991CB93D, 0x273C607B30F68FAE, 0xE02D4247CAC8D41B, 0xA2DDA3AC6322E288,
   0xBE992B5F8BDB8C5C, 0xFC69CAB42231BACF, 0x3B78E888D80FE17A, 0x7988096371E5D7E9,
   0xF7AA4D1A85996083, 0xB55AACF12C735610, 0x724B8ECDD64D0DA5, 0x30BB6F267FA73B36,
   0x4AC29F2A07BFD00D, 0x08327EC1AE55E69E, 0xCF235CFD546BBD2B, 0x8DD3BD16FD818BB8,
   0x03F1F96F09FD3CD2, 0x41011884A0170A41, 0x86103AB85A2951F4, 0xC4E0DB53F3C36767,
   0xD8A453A01B3A09B3, 0x9A54B24BB2D03F20, 0x5D45907748EE6495, 0x1FB5719CE1045206,
   0x919735E51578E56C, 0xD367D40EBC92D3FF, 0x1476F63246AC884A, 0x568617D9EF46BED9,
   0xE085162AB69D5E3C, 0xA275F7C11F7768AF, 0x6564D5FDE549331A, 0x279434164CA30589,
   0xA9B6706FB8DFB2E3, 0xEB46918411358470, 0x2C57B3B8EB0BDFC5, 0x6EA7525342E1E956,
   0x72E3DAA0AA188782, 0x30133B4B03F2B111, 0xF7021977F9CCEAA4, 0xB5F2F89C5026DC37,
   0x3BD0BCE5A45A6B5D, 0x79205D0E0DB05DCE, 0xBE317F32F78E067B, 0xFCC19ED95E6430E8,
   0x86B86ED5267CDBD3, 0xC4488F3E8F96ED40, 0x0359AD0275A8B6F5, 0x41A94CE9DC428066,
   0xCF8B0890283E370C, 0x8D7BE97B81D4019F, 0x4A6ACB477BEA5A2A, 0x089A2AACD2006CB9,
   0x14DEA25F3AF9026D, 0x562E43B4931334FE, 0x913F6188692D6F4B, 0xD3CF8063C0C759D8,
   0x5DEDC41A34BBEEB2, 0x1F1D25F19D51D821, 0xD80C07CD676F8394, 0x9AFCE626CE85B507
        };

        public static ulong crc64(byte[] s)
        {
            var crc = 0xffffffffffffffff;
            for (int j = 0; j < s.Length; j++)
            {
                var b = (crc >> 56) ^ s[j];
                crc = (crc << 8) & 0xffffffffffffffff ^ CRC64_Table[b];
            }

            return crc;
        }

        static int ReadInt32(Stream stream)
        {
            byte[] data = new byte[4];
            stream.Read(data, 0, 4);
            Array.Reverse(data);
            return BitConverter.ToInt32(data, 0);
        }

        static byte[] GetSporeSection(string path)
        {
            var stream = new FileStream(path, FileMode.Open, FileAccess.Read, FileShare.Read);

            // Skip magic
            stream.Seek(8, SeekOrigin.Begin);

            Int32 typeCode = 0;
            while (typeCode != 0x49454E44)
            {
                int length = ReadInt32(stream);
                typeCode = ReadInt32(stream);
                Console.WriteLine("Reading type code " + typeCode + ", length " + length); // KYLE EDIT
                if (typeCode == 0x73704F72)  // spOr
                {
                    Console.WriteLine("Extra data found.");
                }
                stream.Seek(length, SeekOrigin.Current);
                ReadInt32(stream);   // crc, we don't care
            }

            if (stream.Position == stream.Length)
            {
                Console.WriteLine("No extra data found.");
                return null;
            }
            else
            {
                int length = ReadInt32(stream);
                typeCode = ReadInt32(stream);
                if (typeCode == 0x73704F72)  // spOr
                {
                    Console.WriteLine("Extra data found.");
                    byte[] data = new byte[length];
                    stream.Read(data, 0, length);
                    return data;
                }
                else
                {
                    Console.WriteLine("No valid extra data found.");
                    return null;
                }
            }
        }

        public static void ReadPNG(string path, string outputPath, string rawOutputPath = null)
        {

            FileStream imageStream = new FileStream(path, FileMode.Open, FileAccess.Read, FileShare.Read);
            byte[] extraData = GetSporeSection(path);
            if (extraData != null)
            {
                Console.Out.WriteLine(extraData.Length);
            }

            Bitmap img = new Bitmap(imageStream);

            int i = 0;
            byte[] imageData = new byte[img.Width * img.Height * 4];
            for (int y = 0; y < img.Height; ++y)
            {
                for (int x = 0; x < img.Width; ++x)
                {
                    var pixel = img.GetPixel(x, y);
                    imageData[i + 0] = pixel.B;
                    imageData[i + 1] = pixel.G;
                    imageData[i + 2] = pixel.R;
                    imageData[i + 3] = pixel.A;
                    i += 4;
                }
            }

            var decoder = new Decoder(imageData);
            byte[] lengthData = new byte[8];  // magic, length
            decoder.Decode(lengthData);
            int decodedLength = BitConverter.ToInt32(lengthData, 4);

            // KYLEDIT
            if (decodedLength < 0)
            {
                decodedLength = -decodedLength;
            }

            byte[] decodedData = new byte[decodedLength];
            int realLength = decoder.Decode(decodedData);

            Console.Out.WriteLine("expected: " + decodedLength);
            Console.Out.WriteLine("real: " + realLength);

            // Big creations need this, extra data in the PNG
            if (extraData != null)
            {
                /*byte[] oldData = decodedData;
                decodedData = new byte[oldData.Length + extraData.Length];  // - 0x14 ?

                System.Array.Copy(oldData, 0, decodedData, 0, oldData.Length);
                System.Array.Copy(extraData, 0, decodedData, oldData.Length, extraData.Length);*/

                decodedData = new byte[extraData.Length - 0x14];
                System.Array.Copy(extraData, 8, decodedData, 0, decodedData.Length);
            }

            if (rawOutputPath != null)
            {
                File.WriteAllBytes(rawOutputPath, decodedData);
            }

            using (InflaterInputStream decompressionStream = new InflaterInputStream(new MemoryStream(decodedData, false)))
            {
                FileStream outputStream = new FileStream(outputPath, FileMode.Create);
                decompressionStream.CopyTo(outputStream);
                outputStream.Close();
            }
        }

        static void Main(string[] args)
        {
            string path = "OCtest2.png";
            string rawPath = "test.png.xml";
            string output = "test_out.xml";

            ReadPNG(path, output, rawPath);

            Console.In.Read();
        }
    }
}