A designer did a design for me. It is in Adobe llustrator. In order to write my program, I need to export sublayers one by one to png files. How can I do that?
It actually may be easier to export the AI file to a Photoshop file, then use Photoshop to export (Save for Web) to png.
Within Ai, you'll have to turn visibility off for everything layer/sublayer other than the sublayer you want to save... save for web. And then turn on another sub layer and repeat until all files have been exported. There's no automated way built into Illustrator to export or save layers (or sublayers) as individual files.
However, if you export the .ai file as a .psd with layers in tact (assuming there's no transparency or blending modes used in AI), Photoshop does offer scripts or automated ways to export layers as files.
In the end, it really all depends upon the artwork. Some Ai art exports to psd just fine, other Ai art takes some tweaking, which may or may not be feasible for a given project.
The easiest way to do this is by using a script. I created a pretty powerful script recently and blogged about it here:
The blog post contains the script and instructions on how to use the script (and also modify it if you want to).
Hope it helps! /Johan