There is no particular way to write the nonlinear constraint function. It accepts a vector of input values and returns two row vectors of output values (neither of which needs to be the same size as x). In the first output, return one value for each distinct constraint, and the constraints will be considered to be met if all of those values are less than or equal to 0. For the second output, return one value for each distinct constraint, and the constraints will be considered to be met if all of those values are equal to 0.
How you calculate those values is up to you. You can use logical conditions to test ranges. You can use math. You can use image processing tools, whatever you can think of.
