Testing experiment for the signal scaling approach. (a) The design of the test slide with positive spots shown as red spots and the five tested normalization window, indicated by red squares, for a given spot on the array, shown in blue. (b) Comparison of signal intensity before and after normalization using window size 9 on the testing experiment. The two images were computationally reconstructed from the signal files, either without or with normalization. (c) Density plots of signals in the local windows are shown superimposed. The distributions are more similar to each other after the signal normalization using the default window size 9. (d) Variation analysis for positive controls. Five out of six controls showed a decrease of variances after normalization.