{"action":"created","comment":{"url":"https://api.github.com/repos/astrofrog/reproject/pulls/comments/29714731","id":29714731,"diff_hunk":"@@ -0,0 +1,132 @@\n+**********************************\n+Regular celestial images and cubes\n+**********************************\n+\n+One of the most common types of data to reproject are celestial images or\n+n-dimensional data (such as spectral cubes) where two of the axes are\n+celestial. There are several existing algorithms that can be used to\n+reproject such data:\n+\n+* **Interpolation** (such as nearest-neighbor, bilinear, biquadratic\n+  interpolation and so on). This is the fastest algorithm and is suited to\n+  common use cases, but it is important to note that it is not flux\n+  conserving, and will not return optimal results if the input and output\n+  pixel sizes are very different.\n+\n+* **Drizzling**, which consists of determining the exact overlap fraction of\n+  pixels, and optionally allows pixels to be rescaled before reprojection.\n+  More details can be found `here <here>`__. This method is more accurate\n+  than interpolation but is only suitable for images where the field of view\n+  is small so that pixels are well approximated by rectangles in world\n+  coordinates. This is slower but more accurate than interpolation for small\n+  fields of view.\n+\n+* Computing the **exact overlap** of pixels on the sky by treating them as\n+  **four-sided spherical polygons** on the sky and computing spherical polygon\n+  intersection. This is essentially an exact form of drizzling, and should be\n+  appropriate for any field of view. However, this comes at a significant\n+  performance cost. This is the algorithm used by the `Montage\n+  <http://montage.ipac.caltech.edu/index.html>`_ package, and we have\n+  implemented it here using the same core algorithm.\n+\n+Currently, this package implements interpolation and spherical polygon\n+intersection.\n+\n+The reprojection/resampling is always done assuming that the image is in\n+**surface brightness units**. For example, if you have an image with a constant\n+value of 1, reprojecting the image to an image with twice as high resolution\n+will result in an image where all pixels are all 1.","path":"docs/celestial.rst","position":null,"original_position":38,"commit_id":"803bfd401b46c61a88a386a900060e3d1cd99987","original_commit_id":"41be0bd05cf0b2382d1ae75a8683fb126f945a84","user":{"login":"astrofrog","id":314716,"avatar_url":"https://avatars.githubusercontent.com/u/314716?v=3","gravatar_id":"","url":"https://api.github.com/users/astrofrog","html_url":"https://github.com/astrofrog","followers_url":"https://api.github.com/users/astrofrog/followers","following_url":"https://api.github.com/users/astrofrog/following{/other_user}","gists_url":"https://api.github.com/users/astrofrog/gists{/gist_id}","starred_url":"https://api.github.com/users/astrofrog/starred{/owner}{/repo}","subscriptions_url":"https://api.github.com/users/astrofrog/subscriptions","organizations_url":"https://api.github.com/users/astrofrog/orgs","repos_url":"https://api.github.com/users/astrofrog/repos","events_url":"https://api.github.com/users/astrofrog/events{/privacy}","received_events_url":"https://api.github.com/users/astrofrog/received_events","type":"User","site_admin":false},"body":"Done","created_at":"2015-05-05T21:25:02Z","updated_at":"2015-05-05T21:25:02Z","html_url":"https://github.com/astrofrog/reproject/pull/67#discussion_r29714731","pull_request_url":"https://api.github.com/repos/astrofrog/reproject/pulls/67","_links":{"self":{"href":"https://api.github.com/repos/astrofrog/reproject/pulls/comments/29714731"},"html":{"href":"https://github.com/astrofrog/reproject/pull/67#discussion_r29714731"},"pull_request":{"href":"https://api.github.com/repos/astrofrog/reproject/pulls/67"}}},"pull_request":{"url":"https://api.github.com/repos/astrofrog/reproject/pulls/67","id":34648579,"html_url":"https://github.com/astrofrog/reproject/pull/67","diff_url":"https://github.com/astrofrog/reproject/pull/67.diff","patch_url":"https://github.com/astrofrog/reproject/pull/67.patch","issue_url":"https://api.github.com/repos/astrofrog/reproject/issues/67","number":67,"state":"open","locked":false,"title":"Refactor API and docs","user":{"login":"astrofrog","id":314716,"avatar_url":"https://avatars.githubusercontent.com/u/314716?v=3","gravatar_id":"","url":"https://api.github.com/users/astrofrog","html_url":"https://github.com/astrofrog","followers_url":"https://api.github.com/users/astrofrog/followers","following_url":"https://api.github.com/users/astrofrog/following{/other_user}","gists_url":"https://api.github.com/users/astrofrog/gists{/gist_id}","starred_url":"https://api.github.com/users/astrofrog/starred{/owner}{/repo}","subscriptions_url":"https://api.github.com/users/astrofrog/subscriptions","organizations_url":"https://api.github.com/users/astrofrog/orgs","repos_url":"https://api.github.com/users/astrofrog/repos","events_url":"https://api.github.com/users/astrofrog/events{/privacy}","received_events_url":"https://api.github.com/users/astrofrog/received_events","type":"User","site_admin":false},"body":"This is a large refactor that does the following:\r\n\r\n* Complete re-write of the docs\r\n* Expose functions for different algorithms (e.g. ``reproject_interpolation``, etc.)\r\n* New high-level HEALPIX functions\r\n\r\nI'm actually not sure if we need the 'high-level' ``reproject`` anymore now because it doesn't really add much and makes it harder to pass arguments to the sub-functions. 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