using System;

using System.Net; 

using System.Collections.Generic;

using System.IO;

using System.Drawing;

using System.Linq;

using System.Diagnostics; 

​

public class Program

{

    //https://stackoverflow.com/questions/111345/getting-image-dimensions-without-reading-the-entire-file/60667939#60667939

    //DecodeWebP reads only lossless :( 

    //My version improves DecodeWebP to read all webp formats, lossy, lossless and extended! 

    //http://metadataconsulting.blogspot.com/2020/09/CSharp-dotNET-How-to-get-image-dimensions-from-header-of-webP-for-all-formats-lossy-lossless-extended-partially-load-image.html

    internal static class ImageHelper

    {

        const string errorMessage = "Could not recognise image format.";

​

        private static Dictionary<byte[], Func<BinaryReader, Size>> imageFormatDecoders = new Dictionary<byte[], Func<BinaryReader, Size>>()

        {

            { new byte[] { 0x42, 0x4D }, DecodeBitmap },

            { new byte[] { 0x47, 0x49, 0x46, 0x38, 0x37, 0x61 }, DecodeGif },

            { new byte[] { 0x47, 0x49, 0x46, 0x38, 0x39, 0x61 }, DecodeGif },

            { new byte[] { 0x89, 0x50, 0x4E, 0x47, 0x0D, 0x0A, 0x1A, 0x0A }, DecodePng },

            { new byte[] { 0xff, 0xd8 }, DecodeJfif },

            { new byte[] { 0x52, 0x49, 0x46, 0x46 }, DecodeWebP },

        };

​

        /// <summary>        

        /// Gets the dimensions of an image.        

        /// </summary>        

        /// <param name="path">The path of the image to get the dimensions of.</param>        

        /// <returns>The dimensions of the specified image.</returns>        

        /// <exception cref="ArgumentException">The image was of an unrecognised format.</exception>            

        public static Size GetDimensions(BinaryReader binaryReader)

        {

            int maxMagicBytesLength = imageFormatDecoders.Keys.OrderByDescending(x => x.Length).First().Length;

            byte[] magicBytes = new byte[maxMagicBytesLength];

            for (int i = 0; i < maxMagicBytesLength; i += 1)

            {

                magicBytes[i] = binaryReader.ReadByte();

                foreach (var kvPair in imageFormatDecoders)

                {

                    if (StartsWith(magicBytes, kvPair.Key))

                    {

                        return kvPair.Value(binaryReader);

                    }

                }

            }

​

            throw new ArgumentException(errorMessage, "binaryReader");

        }

        /// <summary>

        /// Gets the dimensions of an image.

        /// </summary>

        /// <param name="path">The path of the image to get the dimensions of.</param>

        /// <returns>The dimensions of the specified image.</returns>

        /// <exception cref="ArgumentException">The image was of an unrecognized format.</exception>

        public static Size GetDimensions(string path)

        {

            using (BinaryReader binaryReader = new BinaryReader(File.OpenRead(path)))

            {

                try

                {

                    return GetDimensions(binaryReader);

                }

                catch (ArgumentException e)

                {

                    if (e.Message.StartsWith(errorMessage))

                    {

                        throw new ArgumentException(errorMessage, "path", e);

                    }

                    else

                    {

                        throw e;

                    }

                }

            }

        }

         /// <summary>

        /// Gets the dimensions of an image.

        /// </summary>

        /// <param name="path">The path of the image to get the dimensions of.</param>

        /// <returns>The dimensions of the specified image.</returns>

        /// <exception cref="ArgumentException">The image was of an unrecognized format.</exception>

        public static Size GetDimensions(MemoryStream ms)

        {

            using (BinaryReader binaryReader = new BinaryReader(ms))

            {

                try

                {

                    return GetDimensions(binaryReader);

                }

                catch (ArgumentException e)

                {

                    if (e.Message.StartsWith(errorMessage))

                    {

                        throw new ArgumentException(errorMessage, "path", e);

                    }

                    else

                    {

                        throw e;

                    }

                }

            }

        }

​

​

        private static bool StartsWith(byte[] thisBytes, byte[] thatBytes)

        {

            for (int i = 0; i < thatBytes.Length; i += 1)

            {

                if (thisBytes[i] != thatBytes[i])

                {

                    return false;

                }

            }

​

            return true;

        }

​

        private static short ReadLittleEndianInt16(BinaryReader binaryReader)

        {

            byte[] bytes = new byte[sizeof(short)];

​

            for (int i = 0; i < sizeof(short); i += 1)

            {

                bytes[sizeof(short) - 1 - i] = binaryReader.ReadByte();

            }

            return BitConverter.ToInt16(bytes, 0);

        }

​

        private static int ReadLittleEndianInt32(BinaryReader binaryReader)

        {

            byte[] bytes = new byte[sizeof(int)];

            for (int i = 0; i < sizeof(int); i += 1)

            {

                bytes[sizeof(int) - 1 - i] = binaryReader.ReadByte();

            }

            return BitConverter.ToInt32(bytes, 0);

        }

​

        private static Size DecodeBitmap(BinaryReader binaryReader)

        {

            binaryReader.ReadBytes(16);

            int width = binaryReader.ReadInt32();

            int height = binaryReader.ReadInt32();

            return new Size(width, height);

        }

​

        private static Size DecodeGif(BinaryReader binaryReader)

        {

            int width = binaryReader.ReadInt16();

            int height = binaryReader.ReadInt16();

            return new Size(width, height);

        }

​

        private static Size DecodePng(BinaryReader binaryReader)

        {

            binaryReader.ReadBytes(8);

            int width = ReadLittleEndianInt32(binaryReader);

            int height = ReadLittleEndianInt32(binaryReader);

            return new Size(width, height);

        }

​

        private static Size DecodeJfif(BinaryReader binaryReader)

        {

            while (binaryReader.ReadByte() == 0xff)

            {

                byte marker = binaryReader.ReadByte();

                short chunkLength = ReadLittleEndianInt16(binaryReader);

                if (marker == 0xc0 || marker == 0xc2) // c2: progressive

                {

                    binaryReader.ReadByte();

                    int height = ReadLittleEndianInt16(binaryReader);

                    int width = ReadLittleEndianInt16(binaryReader);

                    return new Size(width, height);

                }

​

                if (chunkLength < 0)

                {

                    ushort uchunkLength = (ushort)chunkLength;

                    binaryReader.ReadBytes(uchunkLength - 2);

                }

                else

                {

                    binaryReader.ReadBytes(chunkLength - 2);

                }

            }

​

            throw new ArgumentException(errorMessage);

        }

        //Other libs did not do it 

        //https://github.com/JosePineiro/WebP-wrapper/blob/master/WebPTest/WebPWrapper.cs

        //https://github.com/JimBobSquarePants/ImageProcessor/blob/6092da59e9aa4975e564002ef3c782a8f6bf3384/src/Plugins/ImageProcessor/ImageProcessor.Plugins.WebP/Imaging/Formats/WebPFormat.cs

        //fast

        private static Size DecodeWebP(BinaryReader binaryReader)

        {

            //https://developers.google.com/speed/webp/docs/riff_container

            //var riffseg = binaryReader.ReadBytes(4); //already offset 4 bytes 

            //var sizebytes = binaryReader.ReadBytes(4); // Size

​

            var size = binaryReader.ReadUInt32(); // Size - start at offset 4 

            var webp = binaryReader.ReadBytes(4); // start 8 offset

​

            var type = binaryReader.ReadBytes(4); // start 12 offset - VP8[ ] determination

​

            string VP8Type = System.Text.Encoding.UTF8.GetString(type);

            Console.WriteLine("VP8Type=\""+VP8Type+"\""); 

​

            int x = 0; 

            int y = 0;

​

            if (VP8Type == "VP8X") //Extra format - https://developers.google.com/speed/webp/docs/riff_container#extended_file_format

            { 

                //skip 32 bits or 8 bytes for Alpha, Exif, XMP flags... in VP8X header

                binaryReader.ReadBytes(8);

​

                byte[] w = binaryReader.ReadBytes(3); //24bits for width

​

                x = 1 + (w[2] << 16 | w[1] << 8 | w[0]); //little endian

​

                byte[] h = binaryReader.ReadBytes(3); //24bits for height

​

                y = 1 + (h[2] << 16 | h[1] << 8 | h[0]); 

​

                return new Size(x, y);

​

            }

            else if (VP8Type == "VP8L") //Lossless - https://developers.google.com/speed/webp/docs/webp_lossless_bitstream_specification#2_riff_header 

            {

                binaryReader.ReadBytes(4); //size

                byte[] sig = binaryReader.ReadBytes(1); //0x2f->47 1 byte signature

                if (sig[0] != 47) new Size(0, 0); 

​

                byte[] wh = binaryReader.ReadBytes(4); //width and height in 1 read

                x = 1 + (((wh[1] & 0x3F) << 8) | wh[0]); //{1 + ((($b1 & 0x3F) << 8) | $b0)} - https://blog.tcl.tk/38137  

                y = 1 + (((wh[3] & 0xF) << 10) | (wh[2] << 2) | ((wh[1] & 0xC0) >> 6)); //{1 + ((($b3 & 0xF) << 10) | ($b2 << 2) | (($b1 & 0xC0) >> 6))}]

​

                return new Size(x, y);

​

            }

            else if (VP8Type == "VP8 ") //Lossy - https://tools.ietf.org/html/rfc6386#section-9.1

            {

​

                //Lossy - https://tools.ietf.org/html/rfc6386#section-9.1 hard to decipher

                //pc->Width      = swap2(*(unsigned short*)(c+3))&0x3fff;  0x3fff -> 16383 decimal  swap2 - big or little indian depending on machine 

                //pc->Height     = swap2(*(unsigned short*)(c+5))&0x3fff;

                //https://blog.tcl.tk/38137 - much better

                binaryReader.ReadBytes(7); //move to offset 23 or 0x17, 23-12+4=7 - open webp lossy file https://developers.google.com/speed/webp/gallery1

​

                byte[] frameTag = binaryReader.ReadBytes(3); //$b0 != 0x9d->157  || $b1 != 0x01>1 || $b2 != 0x2a->  42 

                if (frameTag[0] != 157 && frameTag[0] != 1 && frameTag[0] != 42) return new Size(0, 0); //invalid webp file

​

                //reads 2-bytes which is 16-bits, but we want only 14bits, so and it to 14 bits

                x = binaryReader.ReadUInt16() & 0x3fff;    //$width & 0x3fff -> & 0b00_11111111111111 c#7.0 above only

                y = binaryReader.ReadUInt16() & 0x3fff;    //$height & 0x3fff

                return new Size(x, y);

            }

            return new Size(0, 0);

        }

​

    }

    public static string GetFileNameFromURL(string hrefLink) //hack

    {

        string[] parts = hrefLink.Split('/');

        string fileName = string.Empty;

​

        if (parts.Length > 0)

            fileName = parts[parts.Length - 1];

        else

            fileName = hrefLink;

​

        return fileName;

    }

​

    public static void Main()

    {

        Stopwatch sw = new Stopwatch(); 

        //string webpURL = "https://www.gstatic.com/webp/gallery/1.sm.webp";//Lossy

        //string webpURL = "https://www.gstatic.com/webp/gallery3/2_webp_ll.webp";//Lossless

        //string webpURL = "https://www.gstatic.com/webp/gallery3/1_webp_a.webp";//Extended with alpha channel

        //string webpURL = "https://mathiasbynens.be/demo/animated-webp-supported.webp"; //animated

        //string webpURL = "http://blog.mindworkshop.com/image/webp003.webp"; //animal resource was removed

        string webpURL ="https://1.bp.blogspot.com/-Q2kBYUdM6fc/X2TQpg0fxkI/AAAAAAAAMog/Tqr64JOmRbYgK2Avr36xx-Lg7q8Qu7KNgCNcBGAsYHQ/w320-h240/GenevaDrive.webp";

        string webpfile = GetFileNameFromURL(webpURL); 

        Size webpSize = new Size(); 

        Stopwatch stp = new Stopwatch();

        WebClient wc = new WebClient();

        using (MemoryStream stream = new MemoryStream(wc.DownloadData(webpURL)))

        {

            stp.Start(); 

            webpSize = ImageHelper.GetDimensions(stream); 

            stp.Stop(); 

        }

        Console.WriteLine("WebP file \"{0}\" has dimensions [{1}w X {2}h] in {3}ms.", webpfile, webpSize.Width, webpSize.Height, stp.ElapsedMilliseconds);

        stp.Reset();    

        using (MemoryStream stream = new MemoryStream(wc.DownloadData(webpURL)))

        {

            stp.Start(); 

            Image imageS = Image.FromStream(stream);    

            stp.Stop(); 

            Console.WriteLine("WebP file \"{0}\" has dimensions [{1}w X {2}h] in {3}ms, image obj from full stream.", webpfile, imageS.Width, imageS.Height, stp.ElapsedMilliseconds);

        }

    }

}