{"action":"opened","issue":{"url":"https://api.github.com/repos/Theano/Theano/issues/3928","labels_url":"https://api.github.com/repos/Theano/Theano/issues/3928/labels{/name}","comments_url":"https://api.github.com/repos/Theano/Theano/issues/3928/comments","events_url":"https://api.github.com/repos/Theano/Theano/issues/3928/events","html_url":"https://github.com/Theano/Theano/issues/3928","id":128567626,"number":3928,"title":"Bilinear interpolation for upsampling images by an int factor","user":{"login":"lamblin","id":178249,"avatar_url":"https://avatars.githubusercontent.com/u/178249?v=3","gravatar_id":"","url":"https://api.github.com/users/lamblin","html_url":"https://github.com/lamblin","followers_url":"https://api.github.com/users/lamblin/followers","following_url":"https://api.github.com/users/lamblin/following{/other_user}","gists_url":"https://api.github.com/users/lamblin/gists{/gist_id}","starred_url":"https://api.github.com/users/lamblin/starred{/owner}{/repo}","subscriptions_url":"https://api.github.com/users/lamblin/subscriptions","organizations_url":"https://api.github.com/users/lamblin/orgs","repos_url":"https://api.github.com/users/lamblin/repos","events_url":"https://api.github.com/users/lamblin/events{/privacy}","received_events_url":"https://api.github.com/users/lamblin/received_events","type":"User","site_admin":false},"labels":[],"state":"open","locked":false,"assignee":null,"milestone":null,"comments":0,"created_at":"2016-01-25T15:56:34Z","updated_at":"2016-01-25T15:56:34Z","closed_at":null,"body":"Upsampling images by an int factor (doubling, tripling, ...) can be done by computing `conv2d_grad_wrt_inputs` with a specially-crafted kernel (and taking care of the borders).\r\nWith `conv2d_grad_wrt_...` is part of `theano.nnet`, we could add the wrapper to make it available easily.\r\n\r\nFor large upsampling factors, it is also faster to decouple horizontal and vertical upsampling, and apply the operation twice, with a row kernel and a column kernel."}}