1. A computer-implemented method comprising: receiving an input image; generating a full object mask by providing the input image to a first deep neural network object detector that produces a full object mask for an object of a particular object type depicted in the input image, wherein the full object mask identifies regions of the input image that correspond to the object and regions of the input image that do not correspond to the object; generating a partial object mask by providing the input image to a second deep neural network object detector that produces a partial object mask for a portion of the object of the particular object type depicted in the input image; and determining a bounding box for the object in the image using the full object mask and the partial object mask.