PNG images are compressed and slow

[alouty]

http://www.webpagetest.org/result/121127...1/details/

Item 21 to 28. Most of them are repeated images.

I don't know why test shown that there are compressed. The loading time for those images also slow compare to their size...

Code:

<IfModule mod_mime.c>
AddType application/x-javascript .js
AddType text/css .css
</IfModule>
<IfModule mod_deflate.c>
AddOutputFilterByType DEFLATE text/css application/x-javascript text/x-component text/html text/richtext image/svg+xml text/plain text/xsd text/xsl text/xml image/x-icon application/javascript
<IfModule mod_setenvif.c>
  BrowserMatch ^Mozilla/4 gzip-only-text/html
  BrowserMatch ^Mozilla/4\.0[678] no-gzip
  BrowserMatch \bMSIE !no-gzip !gzip-only-text/html
</IfModule>
<IfModule mod_headers.c>
  Header append Vary User-Agent env=!dont-vary
</IfModule>
</IfModule>

[andydavies]

(11-27-2012 11:54 AM)alouty Wrote:  http://www.webpagetest.org/result/121127...1/details/

Item 21 to 28. Most of them are repeated images.

I don't know why test shown that there are compressed. The loading time for those images also slow compare to their size...

Based on the response headers the images aren't being gzipped see http://www.webpagetest.org/result/121128...#request22 for example.

How are the images stored?

TTFB i.e. time between request being made and the start of response received is slow, which suggests either the request takes a long time to get there or the server is slow generating the response.

If you look at request 22 for example 2757ms to receive a response but only 1ms to download it (it probably fits in a single TCP packet)

Most of the images are pretty small, have you thought about using datauris or a sprite image?

[alouty]

I looked at Full Optimization Checklist and there are 82% compresss img and from 18 to last img are checked. Thus I thought there were compressed...

Those img are repeated img and I excluded them from sprites. At least I tried included them and applied to website but I can see other imgs in the sprite.

I did informed my host regarding TTFB and webpagetest but they told me it mostly test scripts or something like that... I asked them to reduced it without increasing the resources.

[pmeenan]

Image compression looks at JPEG images and looks for an opportunity to save bytes by compressing them FURTHER (not that they aren't compressed at all). It is super-conservative and tries re-compressing jpeg images at a quality level of 85 which should not have any perceivable visual difference.

[alouty]

It seems that when I applied subdomain like images1.domain.com/mod/ to those images will make them load longer. Now I removed it and just put /mod/xxx.png...

Any reason why this happen? I thought it could help to reduce loading time but not increase them...

http://www.webpagetest.org/result/121130...1/details/

[pmeenan]

A new sub-domain (sharding) has some start-up cost where the browser has to do the DNS lookup and establish new connections. It usually only pays off if you have a LOT of static content that you need to serve.