{"action":"created","issue":{"url":"https://api.github.com/repos/mapnik/mapnik/issues/2923","labels_url":"https://api.github.com/repos/mapnik/mapnik/issues/2923/labels{/name}","comments_url":"https://api.github.com/repos/mapnik/mapnik/issues/2923/comments","events_url":"https://api.github.com/repos/mapnik/mapnik/issues/2923/events","html_url":"https://github.com/mapnik/mapnik/issues/2923","id":90535193,"number":2923,"title":"remove pixel demultiply from agg_renderer","user":{"login":"springmeyer","id":20300,"avatar_url":"https://avatars.githubusercontent.com/u/20300?v=3","gravatar_id":"","url":"https://api.github.com/users/springmeyer","html_url":"https://github.com/springmeyer","followers_url":"https://api.github.com/users/springmeyer/followers","following_url":"https://api.github.com/users/springmeyer/following{/other_user}","gists_url":"https://api.github.com/users/springmeyer/gists{/gist_id}","starred_url":"https://api.github.com/users/springmeyer/starred{/owner}{/repo}","subscriptions_url":"https://api.github.com/users/springmeyer/subscriptions","organizations_url":"https://api.github.com/users/springmeyer/orgs","repos_url":"https://api.github.com/users/springmeyer/repos","events_url":"https://api.github.com/users/springmeyer/events{/privacy}","received_events_url":"https://api.github.com/users/springmeyer/received_events","type":"User","site_admin":false},"labels":[],"state":"open","locked":false,"assignee":null,"milestone":null,"comments":4,"created_at":"2015-06-24T01:30:25Z","updated_at":"2015-08-14T08:57:27Z","closed_at":null,"body":"Now that we track the premultiplied status on images I think we should consider:\r\n\r\n - [ ] stop calling `demultiply_alpha` at https://github.com/mapnik/mapnik/blob/master/src/agg/agg_renderer.cpp#L202\r\n - [ ] only demultiply during encoding when needed (like tiff supports premultipled pixes, but PNG does not, right?) \r\n\r\nThe benefit of this would be:\r\n\r\n - If you want to take an image that goes through a renderer and then composite it to another image this would avoid needing to premultiply again.\r\n - Formats that support premultiplied pixels would avoid the speed cost of demultiply\r\n - Formats that do not support alpha would avoid the speed cost of demultiply (jpeg)\r\n - when needed the demultiplication might be able to be done during an existing loop over the pixels\r\n\r\n/cc @artemp for comments"},"comment":{"url":"https://api.github.com/repos/mapnik/mapnik/issues/comments/131030912","html_url":"https://github.com/mapnik/mapnik/issues/2923#issuecomment-131030912","issue_url":"https://api.github.com/repos/mapnik/mapnik/issues/2923","id":131030912,"user":{"login":"artemp","id":59056,"avatar_url":"https://avatars.githubusercontent.com/u/59056?v=3","gravatar_id":"","url":"https://api.github.com/users/artemp","html_url":"https://github.com/artemp","followers_url":"https://api.github.com/users/artemp/followers","following_url":"https://api.github.com/users/artemp/following{/other_user}","gists_url":"https://api.github.com/users/artemp/gists{/gist_id}","starred_url":"https://api.github.com/users/artemp/starred{/owner}{/repo}","subscriptions_url":"https://api.github.com/users/artemp/subscriptions","organizations_url":"https://api.github.com/users/artemp/orgs","repos_url":"https://api.github.com/users/artemp/repos","events_url":"https://api.github.com/users/artemp/events{/privacy}","received_events_url":"https://api.github.com/users/artemp/received_events","type":"User","site_admin":false},"created_at":"2015-08-14T08:57:27Z","updated_at":"2015-08-14T08:57:27Z","body":"@springmeyer @flippmoke - :+1: lets do it! "}}