15. A non-transitory computer readable storage medium storing instructions that, upon being executed by a processor, cause the processor to: receive a search request specifying query content, the query content characterized by query descriptors at a plurality of scales; for each content piece of at least one portion of a content collection: identify a subset of content descriptors of the content piece at each of the plurality of scales, the content descriptors characterizing and describing one or more regions of the content piece, each of the subset of the content descriptors at a respective scale of the plurality of scales corresponding to at least one portion of the query descriptors at the respective scale; determine a size of the query content to generate respective first proportion thresholds with respect to the size of the query content; determine whether a respective first proportion of the subset of the content descriptors at each respective scale is greater than the generated respective first proportion threshold corresponding to the respective scale, the respective first proportion threshold comprising a region size threshold corresponding to the respective scale; and select the content piece for inclusion in a matching content subset of the content collection when at least one of the one or more regions of the subset of content descriptors includes a proportionate size greater than the respective first proportion threshold; and provide the matching content subset in response to the search request.
15. A non-transitory computer readable storage medium storing instructions that, upon being executed by a processor, cause the processor to: receive a search request specifying query content, the query content characterized by query descriptors at a plurality of scales; for each content piece of at least one portion of a content collection: identify a subset of content descriptors of the content piece at each of the plurality of scales, the content descriptors characterizing and describing one or more regions of the content piece, each of the subset of the content descriptors at a respective scale of the plurality of scales corresponding to at least one portion of the query descriptors at the respective scale; determine a size of the query content to generate respective first proportion thresholds with respect to the size of the query content; determine whether a respective first proportion of the subset of the content descriptors at each respective scale is greater than the generated respective first proportion threshold corresponding to the respective scale, the respective first proportion threshold comprising a region size threshold corresponding to the respective scale; and select the content piece for inclusion in a matching content subset of the content collection when at least one of the one or more regions of the subset of content descriptors includes a proportionate size greater than the respective first proportion threshold; and provide the matching content subset in response to the search request. 16. The non-transitory computer readable storage medium of claim 15 , wherein the content descriptors comprise at least: a large scale subset of the content descriptors characterizing larger scale features of the content piece; and a small scale subset of the content descriptors characterizing smaller scale features of the content piece.