Reverting values of image sampler

Hello there,

I am making a perforate window mesh with the help of Image sampler. The image is output from Ecotect analysis, in which the daylight factor range from blue(dark) to yellow(light) suggests shaded region(minimum light gain) to exposed region (max light gain) respectively. Hence to respond this condition Blue region should have larger perforations and yellow should have denser perforations (or none) for efficient performance of mesh.

But as image sampler works, as far i know is by assigning larger values for light colour and lesser for dark colours. 

Please help me out to invert these values with respect to colour spectrum.

Attached are GH file and image used.

Thanks in advance.