Detecting objects in an image includes: extracting core instance features from the image; calculating feature maps at multiscale resolutions from the core instance features; calculating detection boxes from the core instance features; calculating segmentation masks for each detection box of the detection boxes at the multiscale resolutions of the feature maps; merging the segmentation masks at the multiscale resolutions to generate an instance mask for each object detected in the image; refining the confidence scores of the merged segmentation masks by auxiliary networks calculating pixel level metrics; and outputting the instance masks as the detected objects.