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copied!<p>I was looking for something similar a few months earlier. I wanted to read the type, version, height and width of a GIF image but couldn’t find anything useful online.</p> <p>Fortunately in case of GIF, all the required information was in the first 10 bytes:</p> <pre><code>Type: Bytes 0-2 Version: Bytes 3-5 Height: Bytes 6-7 Width: Bytes 8-9 </code></pre> <p>PNG are slightly more complex (width and height are 4-bytes each):</p> <pre><code>Width: Bytes 16-19 Height: Bytes 20-23 </code></pre> <p>As mentioned above, <a href="http://www.wotsit.org/" rel="nofollow noreferrer">wotsit</a> is a good site for detailed specs on image and data formats though the PNG specs at <a href="http://www.libpng.org/pub/png/spec/1.1/PNG-Contents.html" rel="nofollow noreferrer">pnglib</a> are much more detailed. However, I think the Wikipedia entry on <a href="https://en.wikipedia.org/wiki/Portable_Network_Graphics" rel="nofollow noreferrer">PNG</a> and <a href="http://en.wikipedia.org/wiki/Graphics_Interchange_Format" rel="nofollow noreferrer">GIF</a> formats is the best place to start.</p> <p>Here’s my original code for checking GIFs, I have also slapped together something for PNGs:</p> <pre class="lang-cs prettyprint-override"><code>using System; using System.IO; using System.Text; public class ImageSizeTest { public static void Main() { byte[] bytes = new byte[10]; string gifFile = @"D:\Personal\Images&Pics\iProduct.gif"; using (FileStream fs = File.OpenRead(gifFile)) { fs.Read(bytes, 0, 10); // type (3 bytes), version (3 bytes), width (2 bytes), height (2 bytes) } displayGifInfo(bytes); string pngFile = @"D:\Personal\Images&Pics\WaveletsGamma.png"; using (FileStream fs = File.OpenRead(pngFile)) { fs.Seek(16, SeekOrigin.Begin); // jump to the 16th byte where width and height information is stored fs.Read(bytes, 0, 8); // width (4 bytes), height (4 bytes) } displayPngInfo(bytes); } public static void displayGifInfo(byte[] bytes) { string type = Encoding.ASCII.GetString(bytes, 0, 3); string version = Encoding.ASCII.GetString(bytes, 3, 3); int width = bytes[6] | bytes[7] << 8; // byte 6 and 7 contain the width but in network byte order so byte 7 has to be left-shifted 8 places and bit-masked to byte 6 int height = bytes[8] | bytes[9] << 8; // same for height Console.WriteLine("GIF\nType: {0}\nVersion: {1}\nWidth: {2}\nHeight: {3}\n", type, version, width, height); } public static void displayPngInfo(byte[] bytes) { int width = 0, height = 0; for (int i = 0; i <= 3; i++) { width = bytes[i] | width << 8; height = bytes[i + 4] | height << 8; } Console.WriteLine("PNG\nWidth: {0}\nHeight: {1}\n", width, height); } } </code></pre>

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