View Full Version : what is "interlaced" in a photoshop png file save?

code beginner
05-11-2010, 10:54 PM

i'm working with png's fairly often these days. when i save it in photoshop as a png file, it always asks "do you want to save it as an interlaced file?"

i always type yes, because it sounds "better" for some reason. but i have no idea what they are talking about with "interlaced", or how i should decide to select yes or no when it asks if you want to save the file as interlaced.

so if anybody has an idea on this, please let me know!:D

05-12-2010, 11:19 AM
Interlaced is what you see when a JPEG is blurry and becomes sharper while loading. This makes it faster to show the image dimensions and basic content while the image is loading yet where when you don’t save it as interlaced it loads from top to bottom and you only see a part of the image at first.

code beginner
05-13-2010, 12:49 AM
thanks for the information.

from what you're saying, it appears that interlaced increases the file size.

would you know off-hand about what percentage increase the file size is when using interlaced?

it is interesting to see that interlaced is more of a fade into full detail effect, where as the normal type is scans it in line by line.

06-03-2010, 03:09 PM
Interlaced is actually the displaying method of an image. There are 2 types to display modes, 1 is interlaced and other is non-interlaced or progressive scan mode. In progressive scan mode the display displays all the horizontal lines at a time from top to bottom and in non interlaced it display half horizontal lines once and remaining half on next time.
The image you have saved as interlaced means that display will scan it as interlaced input and display it in interlaced mode. The display quality of no-interlaced is always better than interlaced.

06-08-2010, 11:49 AM
Choosing Interlaced means that the whole image is displayed from the get-go, starting at low quality and gradually improving as more data is downloaded to the browser, sort of like coming into focus.

Obviously the speed of the host server pushing the data and the bandwidth of the users connection has a direct bearing on the time it takes to render the web page and graphics.

code beginner
06-09-2010, 12:07 AM
it seems like interlaced is good unless it's a big file