{"action":"created","issue":{"url":"https://api.github.com/repos/mapnik/mapnik/issues/2438","repository_url":"https://api.github.com/repos/mapnik/mapnik","labels_url":"https://api.github.com/repos/mapnik/mapnik/issues/2438/labels{/name}","comments_url":"https://api.github.com/repos/mapnik/mapnik/issues/2438/comments","events_url":"https://api.github.com/repos/mapnik/mapnik/issues/2438/events","html_url":"https://github.com/mapnik/mapnik/issues/2438","id":43832381,"number":2438,"title":"tiff reprojection differences on osx vs linux","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":[{"url":"https://api.github.com/repos/mapnik/mapnik/labels/post3x","name":"post3x","color":"5319e7"}],"state":"open","locked":false,"assignee":null,"milestone":null,"comments":4,"created_at":"2014-09-25T01:03:14Z","updated_at":"2016-03-14T15:20:25Z","closed_at":null,"body":"for `tiff-reprojection-2` the expected image looks like:\r\n\r\n![tiff-reprojection-2-250-250-1 0-agg-reference](https://cloud.githubusercontent.com/assets/20300/4398113/7b7f3146-444f-11e4-8fb8-88d5191c3af2.png)\r\n\r\nWhile on ubuntu precise (with mapnik master built with mapnik-packaging - which should include the same gdal version) I'm seeing:\r\n\r\n![tiff-reprojection-2-250-250-1 0-agg](https://cloud.githubusercontent.com/assets/20300/4398115/8fa75e00-444f-11e4-8e3a-927dc988454e.png)\r\n\r\nWhich is the cause of these test failures:\r\n\r\n```\r\nVisual rendering: 4 failed / 1502 passed\r\n1) 1821 different pixels:\r\n\t/tmp/mapnik-visual-images/tiff-reprojection-2-250-250-1.0-agg.png (actual)\r\n\ttests/visual_tests/images/tiff-reprojection-2-250-250-1.0-agg-reference.png (expected)\r\n2) 1821 different pixels:\r\n\t/tmp/mapnik-visual-images/tiff-reprojection-2-250-250-1.0-cairo.png (actual)\r\n\ttests/visual_tests/images/tiff-reprojection-2-250-250-1.0-cairo-reference.png (expected)\r\n3) 1821 different pixels:\r\n\t/tmp/mapnik-visual-images/tiff-reprojection-2-250-250-2.0-agg.png (actual)\r\n\ttests/visual_tests/images/tiff-reprojection-2-250-250-2.0-agg-reference.png (expected)\r\n4) 1821 different pixels:\r\n\t/tmp/mapnik-visual-images/tiff-reprojection-2-250-250-2.0-cairo.png (actual)\r\n\ttests/visual_tests/images/tiff-reprojection-2-250-250-2.0-cairo-reference.png (expected)\r\n```\r\n\r\nThe test was enabled in https://github.com/mapnik/mapnik/commit/7fdae08ce1e1e67dbde8e9a24c5b7ad30db72043#diff-592b7c68836bded85ad1fb606511547e (and previous images were made up)"},"comment":{"url":"https://api.github.com/repos/mapnik/mapnik/issues/comments/196365293","html_url":"https://github.com/mapnik/mapnik/issues/2438#issuecomment-196365293","issue_url":"https://api.github.com/repos/mapnik/mapnik/issues/2438","id":196365293,"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},"created_at":"2016-03-14T15:20:25Z","updated_at":"2016-03-14T15:20:25Z","body":"Numerical instability is the most likely since this test also starts failing on linux when Mapnik is compiled with g++5: https://github.com/mapnik/mapnik/issues/3336#issuecomment-192047824"}}