23. A system, comprising: at least one processor; and a memory coupled to the at least one processor, wherein the memory stores program instructions, wherein the program instructions are executable by the at least one processor to: determine a plurality of semantic category scores for a digital image via application of a corresponding plurality of classifiers; automatically determine a semantic category profile for the image based on the plurality of semantic category scores, wherein the semantic category profile characterizes semantic content of the image, and is useable to perform semantic based operations with respect to the image; and perform a semantic based operation, wherein the semantic based operation comprises: a search operation based on a semantic similarity measure for a plurality of semantic category profiles for a plurality of digital images, wherein the plurality of semantic category profiles includes the semantic category profile for the image; or a keyword operation based on a semantic similarity measure for a plurality of semantic category profiles for a plurality of digital images, wherein the plurality of semantic category profiles includes the semantic category profile for the image.
23. A system, comprising: at least one processor; and a memory coupled to the at least one processor, wherein the memory stores program instructions, wherein the program instructions are executable by the at least one processor to: determine a plurality of semantic category scores for a digital image via application of a corresponding plurality of classifiers; automatically determine a semantic category profile for the image based on the plurality of semantic category scores, wherein the semantic category profile characterizes semantic content of the image, and is useable to perform semantic based operations with respect to the image; and perform a semantic based operation, wherein the semantic based operation comprises: a search operation based on a semantic similarity measure for a plurality of semantic category profiles for a plurality of digital images, wherein the plurality of semantic category profiles includes the semantic category profile for the image; or a keyword operation based on a semantic similarity measure for a plurality of semantic category profiles for a plurality of digital images, wherein the plurality of semantic category profiles includes the semantic category profile for the image. 29. The system of claim 23 , wherein the digital image is comprised in the plurality of digital images, wherein the program instructions are further executable to: automatically determine the respective semantic similarity measure for each digital image of at least a subset of the plurality of digital images with respect to the first digital image based on the semantic category profile of the first digital image and semantic category profiles of each digital image of the at least a subset of the plurality of digital images, wherein each digital image of the at least a subset of the plurality of digital images has one or more respective keywords; and automatically determine one or more keywords from the respective keywords for association with the first digital image based on the values of the semantic similarity measure.