Hello @Praveen @Helene, I'm performing the same experiment and quantify the GP value. However, I meet with the same problem. I tried your macros, and changed the file name to A.ch00 and A.ch01, but still did not work. I followed the Nature Protocol, but I can't find the choice of "Grays" in "scale color for GP images". Do you use 16_Color.lut instead? I'm really very appreciated if you could provide me any suggestions.