Skip to Content

Stylegala Forums » Forums list » Problem solving

saving PNG's in photoshop

saving PNG's in photoshop

post new topic Post new topic    Reply to topic Reply to topic

Author Message
Yaral

New member
  • Joined: 13 Oct 2006
  • Posts: 35
  • Status: Offline
Reply with quote Post Posted: Fri May 09, 2008 02:00
I've been running into a problem while trying to save a large PNG file with PS (CS3). Using save for web, if I choose PNG 8-bit, I do not get true transparency. I get rough transitions similar to saving as a gif. However, if I save as a 24-bit PNG, I get a large file size (700k).

Does anyone have experience using PNG's? If so, how do you go about saving them?

View user's profile Send private message AIM Address MSN Messenger
 
Sponsor
 
karmedic

New member
  • Joined: 26 May 2008
  • Posts: 1
  • Status: Offline
Reply with quote Post Posted: Mon May 26, 2008 17:52
24bit PNGs support alpha transparency whereas 8 PNGs do not. Since you are saving 8 bits per channel in the 24 bit PNG (and then another 8 bits for the Alpha) the file size will be alot bigger - ie, it's true colour. The trade off with an 8 bit PNG is that a) you get flat transparency and b) you are restricted a 256 colour palette. I will typically only use 24bit PNGs if I require true alpha transparency ... if not i got with another format. For a large image that has many colours and does not require alpha transparency i will typically use JPEG and adjust the lossiness to suit my needs.

hth

View user's profile Send private message
 
objx

New member
  • Joined: 19 May 2008
  • Posts: 4
  • Status: Offline
Reply with quote Post Posted: Tue May 27, 2008 09:01
Remember that 24-bit PNG's isn't supported in IE6 browsers too.(the background gets colored)
There is a javascript-solution for IE6. This will fix the transparency problem, but it's quite alot of code, just to get the transparency working:
http://www.twinhelix.com/css/iepngfix/
_________________
World Maps - Geography Resource

View user's profile Send private message Visit poster's website
 
Bill Posters

Site Moderator
Reply with quote Post Posted: Tue May 27, 2008 11:11
objx wrote:
Remember that 24-bit PNG's isn't supported in IE6 browsers too.(the background gets colored)
There is a javascript-solution for IE6. This will fix the transparency problem, but it's quite alot of code, just to get the transparency working:
http://www.twinhelix.com/css/iepngfix/


Js solutions simply automate the application of a CSS-based solution.
For more control and for fewer instances, simply apply the CSS fix manually via an IE stylesheet.

e.g.

styles.css
#something {
   background: url(/images/bg-something.png);
}


ie-5-6.css
#something {
   background: none;
   filter:progid:DXImageTransform.Microsoft.AlphaImageLoader(src="/images/bg-something.png");
}


IE filtered background images won't tile, so you may need to use an alternative version of the image, large enough to span the desired area.

e.g.

styles.css
#something {
   background: url(/images/bg-something.png);
}


ie-5-6.css
#something {
   background: none;
   filter:progid:DXImageTransform.Microsoft.AlphaImageLoader(src="/images/bg-something-large.png");
}

_________________
aka 'clemi'

View user's profile Send private message
 

Page 1 of 1

post new topic Post new topic    Reply to topic Reply to topic

Display posts from previous:   

Powered by phpBB. © 2001, 2006 phpBB Group & Logo Design