Canvas questions to load images

[Corona]

I am currently running a dot probe task with visual paired stimuli 
(positive, negative). I have a two fold question pertaining to this task:

1) I have about 60 images in one of my trialprocs, and was therefore 
advised to use the canvas option to preload images. I have had little 
success with using this object, particularly because I do not entirely 
understand the concepts of off-screen and on-screen canvas. I have managed 
to write a small script with help from the references guides posted on the 
e-prime website (as well as forums), but am stuck when it comes to the 
following statement:

1.      When preparing the trial:

 

targetCanvas.LoadImage stim 

 

*Image is loaded to the top left corner. We need to define 2 Rect Objects: 
StimLoadRect and StimRect (see Rect object in the E-Basic Help), both the 
size of the images to-be-loaded, but the StimRect at the (Left,Right, 
Top,Bottom) coordinates where the stimulus will be displayed. When we copy 
the image from the offline canvas to the online canvas, we will copy from 
StimLoadRect to StimRect.*

 

2.      To run the stimulus:

 

Display.WaitForVerticalBlank

c.setAttrib "StimOnset", clock.read

cnvs.copy targetCanvas, stimLoadRect, stimRect

sleep(stimDuration)

Display.WaitForVerticalBlank

Cnvs.clear ' or something else that erases the stimulus, can be done in the 
following trial

 

*Bolded lines: *How do I create a stimLoadRect and stimRect image, a is 
asked for? (I did find a script for creating a rect object, but am unsure 
of how to specify dimensions).

I assume that pre-defining images and their locations, means I do not have 
to specify them as a SlideObject? (I am guessing I am completely wrong here 
- please feel free to correct me) . I would also assume that the 
stimDuration, must be defined as an attribute? 

 

Assuming I do not have to go through this convoluted path, I have another 
question. If I could pre-load using the SlideImage and ImageDisplay 
options, I am not sure how to specify the co-ordinates of where I want my 
image to be in the properties section. I know this appears elementary, but 
the actual size of the images are 424 X 283, but when running, part of the 
images are cut off. When I looked at the properties of my slide object, I 
had set the width at 25% . I assumed this was the co-ordinate location in 
relation to the actual screen size. Guessing that this was an error on my 
part, I reset the width to 100%, but that meant that when I looked at the 
slideobject (with the dotted grid), one image seemed to complete cover the 
other image. How do I fit both images, and make sure their dimensions 
remain the same?


I apologize for this rant. I only recently switched to e-prime from using 
Inquisit, and am still trying to get a hang of this software tool.


Thanks a ton for your reply,

Corona

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