The GPU accelerators on Tesseract are only available in TCC (Tesla Compute Cluster) mode and so do not support graphics rendering tasks, only computational tasks.

Can Tesseract run on GPU?

Using Tesseract with OpenCL. Normally Tesseract works with OpenCL Installable Client Drivers (ICD). It tests for available OpenCL drivers at runtime, so a Tesseract binary can work with different GPU hardware on different computers. All you have to do is installing the OpenCL driver for your GPU hardware.

Does OCR use CPU or GPU?

OCR is a CPU HOG. It will take 99% of any single thread when it is running, so putting energy into a more powerful CPU with more threads is not a bad idea.