The sample experiment shows how to design trials for optimal
display loading time without having to use the Canvas
Please keep in mind that if you are currently using E-Prime version
220.127.116.11 or newer, you do not need to use this sample. This sample
is primarily for users who are developing experiments using E-Prime 1.2 only.
E-Studio permits image objects (ImageDisplay, SlideImage) to
vary their contents by using an attribute reference [attrib] in
the Filename property. When this is done, the object will load
the contents of the file just prior to the object running.
This operation can take a long time (100ms) since it requires
obtaining the file contents from hard disk. This loading time
will increase the .OnsetDelay of the object and will require the
object to start later than intended.
To assist in reducing the .OnsetDelay of an object, the author
of an experiment must preload the images. The most robust
option is to use InLine script and the Canvas object. The
Canvas object provides the ability to load an image and display
it to the DisplayDevice in a few operations. The downside to
using the Canvas is that it requires a lot of scripting - including
separate handling of input, responses, and logging. Further,
there are a number of issues to consider when using multiple
Canvas objects and dealing with video memory, system
memory, and operating system swapping. Experiments that
require very quick (< 100ms) transition between images and/or
require many images per trial may be better suited to using the
Canvas scripting object.
As an alternative to using the Canvas, the author of an
experiment can alter the default loading behavior of an image
object by having it load the image contents at the beginning of
the trial. This sample experiment shows an example of how to use this
alternative loading mechanism for both the ImageDisplay and