Well… No. It’s not “garbage” or “non-data”. If the transformation from a source is continuous, then values that land outside the destination encoding range are merely out of range and remain valid representations of image information. You have to deal with how you are going to represent those values within the destination range, but there is nothing very unusual about that when doing such transformations, and choices are well known (various types of clipping, compression, scaling etc. etc.)
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