Get image dimensions from header of WebP for all formats; lossy, lossless and extended and is fast.
Code for reading the header of WebP formats is not commonly available in C# .NET, so I had to go to the WebP Container Specification to build out the code. The code reads the 1st 30 bytes of a webp file only. This is fast, but could be faster, stay tuned.
Geneva Drive.webp is "VP8X" type
Handles animated webp formats as specified by "VP8X" type.
Source Code
using System; using System.Net; using System.Collections.Generic; using System.IO; using System.Drawing; using System.Linq; using System.Diagnostics; public class Program { //Org https://www.codeproject.com/Articles/35978/Reading-Image-Headers-to-Get-Width-and-Height //Mod https://stackoverflow.com/questions/111345/getting-image-dimensions-without-reading-the-entire-file/60667939#60667939 // DecodeWebP reads only lossless :( //My version improved DecodeWebP method to read all webp formats; lossy, lossless and extended. 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 riff = binaryReader.ReadBytes(4); //already offset 4 bytes to read R I F F uint size = binaryReader.ReadUInt32() + 8; // Size - start at offset 4, length+8! https://en.wikipedia.org/wiki/WebP - actual not on disk size var webp = binaryReader.ReadBytes(4); // start 8 offset - https://en.wikipedia.org/wiki/WebP if (webp[0] != 87 && webp[1] != 69 && webp[2] != 66 && webp[3] != 80) //must match W E B P return new Size(0, 0); //or use binaryReader.ReadBytes(8); to avoid skip above var type = binaryReader.ReadBytes(4); // start 12 offset - VP8[ ] determination string VP8Type = System.Text.Encoding.UTF8.GetString(type); Console.WriteLine("VP8Type=\""+VP8Type+"\" of size "+ size.ToString("#,##0")+" bytes."); 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) return 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 this //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 || $b2 != 0x2a-> 42 if (frameTag[0] != 157 || frameTag[1] != 1 || frameTag[2] != 42) return new Size(0, 0); //invalid webp file //reads 2 bytes which is 16-bits, but we want only 14 bits, shrink x = binaryReader.ReadUInt16() & 0x3fff; //$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 string webpURL = "https://file-examples-com.github.io/uploads/2020/03/file_example_WEBP_1500kB.webp"; //1.5 Mb string webpfile = GetFileNameFromURL(webpURL); Size webpSize = new Size(); WebClient wc = new WebClient(); using (MemoryStream stream = new MemoryStream(wc.DownloadData(webpURL))) //this would normally be a path, but can't do that here { sw.Start(); webpSize = ImageHelper.GetDimensions(stream); sw.Stop(); } Console.WriteLine("WebP file \"{0}\" has dimensions [{1}w X {2}h] in {3}ms.", webpfile, webpSize.Width, webpSize.Height, sw.ElapsedMilliseconds); } }
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