Do you want to use the ComputerVisionAPI.OCRV2() function and the ComputerVisionAPI.OCRTextV2() function within your canvas app?
Based on the issue that you mentioned, I have made a test, and the issue is confirmed on my side. Currently, within PowerApps, when you use ComputerVisionAPI.OCRV2() function or the ComputerVisionAPI.OCRTextV2() function, there is no place to provide the Image argument (second argument).
I think this issue may be related to the Computer Vision API (the Image parameter is not be exposed within OCRV2 action and OCRTextV2 action). Currently, within PowerApps, I afraid that there is no way to achieve your needs.
If you would like this feature to be improved within PowerApps, please submit an idea to PowerApps Ideas Forum:
As an alternative solution, you could consider achieve your needs using Microsoft Flow. I have made a test on my side, please take a try with the following workaround:
In addition, you could also consider take a try to create a custom connector based on Computer Vision API within your app to achieve your needs. Please check and see if the following blog or video would help in your scenario: