Abstract: Methods, systems and apparatus for assigning labels to images. In general, in one aspect, a method includes determining, for an image, a first set of labels, each label being determined to be indicative of subject matter of the image based on content feature values of the image, for each label in the first set of labels, determining a second set of labels, each label in the second set of labels determined to be semantically related to the label in the first set of labels, assigning a score to each label in the second sets of labels, and based on the scores assigned to each label in the second sets of labels, assigning one or more of the labels in the second sets of labels to the image.

Abstract: A method and an apparatus to perform replacement halftoning is disclosed. In one embodiment, the method comprises dithering multiple color channels of a pixel of an image to generate a plurality of halftone outputs. Each of the halftones corresponds to a distinct color channel of the pixel. The method further includes creating a virtual color channel from two or more color channels of the plurality of color channels and applying error diffusion to the virtual color channel to generate an error diffusion halftone outputs, and then replacing of the dither output error diffusion halftone outputs.