Will adding gZip compression to my web app improve the performance of loading of large images?

Question

I have a web app that contains a slide show with about 10 large images (100-200k) images. I've heard of people using gZip http compression to help improve the performance of their websites in the past so I started doing a little research on this. I ended up finding the following web.config snipit that claims to do this:

<system.webServer>
  <httpCompression directory="%SystemDrive%\inetpub\temp\IIS Temporary Compressed Files">
    <scheme name="gzip" dll="%Windir%\system32\inetsrv\gzip.dll"/>
    <dynamicTypes>
      <add mimeType="text/*" enabled="true"/>
      <add mimeType="message/*" enabled="true"/>
      <add mimeType="application/javascript" enabled="true"/>
      <add mimeType="*/*" enabled="false"/>
    </dynamicTypes>
    <staticTypes>
      <add mimeType="text/*" enabled="true"/>
      <add mimeType="message/*" enabled="true"/>
      <add mimeType="application/javascript" enabled="true"/>
      <add mimeType="*/*" enabled="false"/>
    </staticTypes>
  </httpCompression>
  <urlCompression doStaticCompression="true" doDynamicCompression="true"/>
</system.webServer>

But after looking at it a little closer this does not appear to do anything for images.

Is using gZip compression for image mimeTypes effective or would I be wasting my time to add it to the above? Can anyone recommend any good strategies for improving the load time of large images?

Side note: Not sure if it makes a difference but the site is hosted on goDaddy.

score 2 · Accepted Answer · edited May 23 '17 at 11:55

2

JPG images, GIF, etc are already compressed formats. Compressing them further isn't going to help much. You should be looking into caching them instead so that the web server returns 304 responses every time a request for the same image is made.

By the way, the Web.config that you posted is not doing compression on images (as it doesn't help).

UPDATE

Configure IIS to return HTTP 304 Status codes on certain file types.

edited May 23 '17 at 11:55

Community

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answered Nov 09 '11 at 06:13

Icarus

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Just to be clear, this would only benefit users returning to the site when it had the same images correct? – Abe Miessler Nov 09 '11 at 06:17
@AbeMiessler: I am afraid not. The first load is going to be painful if the images are too big, but subsequent requests should go super fast provided you configure IIS to cache images. And you should also cache JS & css files. I will link an example on how to configure IIS to return 304 responses but there are many more techniques, such as the use of ETags, minimizing javascript, etc. Follwing all tips given here is usually a good start: http://developer.yahoo.com/yslow/ – Icarus Nov 09 '11 at 06:19
@AbeMiessler: My above answer was to your initial question which apparently you edited. To answer your new question... yes, caching will benefit users returning to the site; there are techniques you can use to improve the load time the first time, but no matter what you do, all images have to come down the wire at some point. – Icarus Nov 09 '11 at 06:21
@AbeMiessler: Check the link I posted. – Icarus Nov 09 '11 at 06:28

Prasanth · Answer 2 · 2011-11-09T06:46:14.807

0

The JPEG format is a compressed format. So no need to compress it again. Think about compressing scripts and css.

Use SquishIt for compressing javascript and CSS.

Try SmushIt from Yahoo to optimise the images

edited Nov 09 '11 at 06:46

answered Nov 09 '11 at 06:39

Prasanth

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Will adding gZip compression to my web app improve the performance of loading of large images?

2 Answers2