Print out a pixel value with serial communication

[aconcagua]

I'd like to ask if there is a method to get the pixel value stored in the GPU RAM and print it out with Serial.print() function of Arduino. The reason I'd like to do that is to learn what the pixel has been change after calling the GD2 functions.
The function might be similar to the function in OpenCV: image.at<int>(i, j)
Thank you!!