How to read the numeric data out of the image sampler

I want to use the lightness data from the picture as the height of the box, to create a wavey sense of the columns, but I do not know how to achieve (31.4 KB)

Attach a file!

Here is one approach (37.9 KB)

Hey, thanks for the reply, but if using the grid, how could I change the intervals, coz I also wanna make the interval having a gradient change

You can position the columns wherever you like, as long as you evaluate the image using this kind of approach to get the heights based on the image. (37.4 KB)