1. A computer-implemented method for identifying pictures in documents, comprising: at a computer system including one or more processors and memory storing one or more programs, the one or more processors executing the one or more programs to perform the operations of: receiving an image representing a page of a document; analyzing the image to identify text objects in the page; generating a masked image by masking out regions of the image including the text objects in the page; identifying groups of pixels in the masked image, wherein a respective group of pixels corresponds to at least one picture in the page; when there is one or more groups of pixels, identifying regions for pictures based on the one or more groups of pixels; and storing metadata tags for the pictures, wherein a respective metadata tag for a respective picture includes information about a respective region for the respective picture.