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Other image layer attributes
The final three image layer attributes are Delay, Wait for user input, and Interlace. Like all
the image layer attributes, their presence is required by the file format (GIF89a), but only one
has any visible effect on an animation as it plays in a web browser. They are described below:
•
Delay - Of the three image layer attributes,
this is the perhaps the most useful. The
delay time measures the time that the
image remains on screen before being
removed and replaced by subsequent
images. The delay time is measured in
hundredths of a second.
•
Wait for user input - This option is
currently not supported in the major
browsers, but it is implemented in dedi-
cated GIF viewers. Setting this option on
an image layer forces the layer to pause the
animation until the user either clicks the
mouse button or presses a key on the
keyboard.
•
Interlace - Interlacing breaks an image
into two separate fields, allowing one field
to download first while waiting for the
other. This gives users an immediate
preview of the image rather than having to
wait for the entire picture to finish down-
loading. Static GIF images (i.e., those with
single image layers) support this, but in an
animated GIF this feature doesn't work on
any image layer except the first. If you
import any GIF images with their interlac-
ing enabled, be sure to deselect the option
inside GIF Animator so that web browsers
won't encounter any problems with them.
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