Canvas questions to load images

[Corona]

Thank you Alphonse, for the quick reply. More for the purpose of 
understanding the code, than anything else, why do you repeat  cnvs.Copy 
offScreenCnvs, myRect, myrect (with myrect twice)? More specifically, how 
is this understood by e-prime? Also, I am guessing I do not have to include 
a slideobject?



On Sunday, September 16, 2012 10:59:26 AM UTC-4, alphonse wrote:
>
>  
> -----------------------------------------------
> 'Prepare stimulus offscreen
> offScreenCnvs.LoadImage stim
>
> 'Define the copy area
> Dim myRect As Rect
> myRect.Left = xMargin
> myRect.Right = xMargin + 60
> myRect.Top = yMargin
> myRect.Bottom = yMargin + 60
>
> 'Copy prepared stimulus to screen
> cnvs.Copy offScreenCnvs, myRect, myRect
> --------------------------------------------------------------------------
>
> At 12:39 AM 17/09/2012, you wrote:
>
> 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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>  
>
>

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