title: Reading image header info without loading the entire image
body: <p>I have a .net 3.5 application that will be dealing with a large number of images. I need to check that the image extension is correct, the image height and width, and the PPI. I do not want to load the entire image into a .net image or bitmap, this will take to long and be to resource intensive. I can not use third party plug-ins or dlls, and of course it needs to be done yesterday.</p>
  
  <p>So, I am reading the initial bytes of the files, checking the "magic" numbers to make sure the image extension matches, and then the height and width of the image for most of the image types I need to handle. This is much faster and less resource intensive. I could use a little help reading the PPI from some of the image types, and two of the types have just stumped me beyond validating the extension so far. </p>
  
  <p>BMP, JPG, GIF, and PNG I need help reading the PPI. </p>
  
  <ul>
  <li>Looking for something like located at offset xx.  </li>
  </ul>
  
  <p>TIF, EPS, and PSD I need help reading height, width, and PPI. </p>
  
  <ul>
  <li><p>I am pretty much stuck on Eps and Psd files, and anything would help.</p></li>
  <li><p>Yes I know about tiflib, it looks great, and way more than I need. A lighter version that handles only the height, width, and PPI would be great. If I have to I can do this, but I'm hoping someone all ready has :-)</p></li>
  </ul>