Hi, I am a new user of Envi and I knew very little about band math. I want to write an expression in band math, but I didn¡¯t know how to write it. Please help me and thank you very much. 255 h(x)= - ¡Æ Pi * Log2 Pi i=0 where: Pi is the probability that the pixel grey value is equal to i; x is the input image variable; LP