1. A system, comprising: one or more processors; and a memory coupled to the one or more processors and storing program instructions executable by the one or more processors to implement an interactive image compositing application configured to: access data in persistent storage representing an image in response to selection of the image; display a copy of the image superimposed over another image; extract an object of interest from the copy of the image; merge the extracted object and the other image to generate and display a preview of a composite image in which the extracted object appears to be inserted in the other image; and subsequent to generating and displaying the preview, render a refined version of the composite image; wherein to render the refined version of the composite image, the application is configured to operate on a representation of a portion of the copy of the image that comprises the object of interest that is at a higher resolution than another representation of the portion of the copy of the image on which the application operates to generate and display the preview of the composite image.