Figure 5

(a) Boxplots of mean red, green, and blue intensities in 188 non-cancerous regions pre- (left boxes) and post- (right boxes) color normalization. While our chosen normalization method works in the stain vector space, not in the RGB space, the range and variation of mean color intensities decreased after normalization, especially in the green channel. This suggests that normalization has reduced the variation in color across the images. (b) Feature PI by family before (lighter bars) and after (darker bars) color normalization. PI was measured across the 188 non-cancerous regions of the four sites before and after those regions were normalized. Color normalization increased instability in every feature family with an especially strong effect on the disorder features. These results suggest that color normalization is inadequate to resolve the problem of feature instability from site variation and may even worsen instability.