Error on submitting a drawing response

[keijiota]

Hello everyone,

I am planning to get a drawing response using a sketchpad plugin. This plugin works perfectly when there is no background image.
When I specify a background image on which I draw, I cannot finish the response. And there is an error message stating
"Uncaught DOMException: Failed to execute 'toDataURL' on 'HTMLCanvasElement': Tainted canvases may not be exported.
at SketchpadPlugin.end_trial at HTMLButtonElement."
Do you have any idea of how to avoid this error? Do I need to pre-process an image I use?

I would be grateful if someone could help me.

Many thanks,
Keiji

[jodeleeuw]

Hi @keijiota,

This is because you are running the experiment locally on your computer, and there are security flags in place in this environment. Here's a relevant stack overflow explainer.

If you run a local server on your machine this will solve the problem. Try the Live Server Extension if you are programming in VS Code; it is easy to use!

[keijiota]

Thank you very much @jodeleeuw
I see the live server extension indeed solves the issue.
Is there any way to run the sketchpad on Gorilla? I still see the same issue when running my code on their platform.
Best,
Keiji

[jodeleeuw]

I'm afraid I don't know much about why it wouldn't work on Gorilla. You may have to ask their support group.

[keijiota]

Thanks again. I found that a simple way to avoid security flags is to turn off the save_final_image.