We can clearly see in many cases of resampling that some pixels are made from the average of several others. This is particularly true in upsample using cubic weighting. We have also said earlier that averaging two pixels in any color space can cause some odd results so this section is some gotchas to look out for and what to do about them. This is an area that I am least familiar with since I only use RGB and dont bother trying to fix these but its worth knowing anyway.
We noted that a blend from red to blue in RGB color space would give deep mauve - ok but look at this. This is an up sample of some colors which have some issues. Some of the corners here are pure green but the other is red & blue (magenta). When we average these two colors together the red & blue from one image drop halfway and the green from the other drops halfway. End result - all halfway to give mid gray ! Now its worth noting that for resample types that dont allow blends like the nearest neighbor then you dont get the issue. Also, it turns out that if you apply a gamma adjustment to the image, resample with a cubic and the apply and reverse gamma adjustment then the problem gets fixed. I havent fully convinced myself why this is true but I am assured it is.