{"action":"created","issue":{"url":"https://api.github.com/repos/Microsoft/Win2D/issues/202","labels_url":"https://api.github.com/repos/Microsoft/Win2D/issues/202/labels{/name}","comments_url":"https://api.github.com/repos/Microsoft/Win2D/issues/202/comments","events_url":"https://api.github.com/repos/Microsoft/Win2D/issues/202/events","html_url":"https://github.com/Microsoft/Win2D/issues/202","id":121919724,"number":202,"title":"Unable to render rgba strokes into transparent offscreen ","user":{"login":"Sebosek","id":372542,"avatar_url":"https://avatars.githubusercontent.com/u/372542?v=3","gravatar_id":"","url":"https://api.github.com/users/Sebosek","html_url":"https://github.com/Sebosek","followers_url":"https://api.github.com/users/Sebosek/followers","following_url":"https://api.github.com/users/Sebosek/following{/other_user}","gists_url":"https://api.github.com/users/Sebosek/gists{/gist_id}","starred_url":"https://api.github.com/users/Sebosek/starred{/owner}{/repo}","subscriptions_url":"https://api.github.com/users/Sebosek/subscriptions","organizations_url":"https://api.github.com/users/Sebosek/orgs","repos_url":"https://api.github.com/users/Sebosek/repos","events_url":"https://api.github.com/users/Sebosek/events{/privacy}","received_events_url":"https://api.github.com/users/Sebosek/received_events","type":"User","site_admin":false},"labels":[],"state":"open","locked":false,"assignee":null,"milestone":null,"comments":3,"created_at":"2015-12-13T13:35:44Z","updated_at":"2015-12-14T22:23:54Z","closed_at":null,"body":"Hi,\r\n\r\nwhen I want to render strokes with transparency (argb(100, 255, 255, 0) in my case) into transparen offset screen; final picture is empty in photoshop, Office Picture Manager and black in system explorer. But when I use classic color, like Colors.Black as pen it work like a charm or when I use Colors.White as background and pen with color argb(100, 255, 255, 0) I works. Am I missing something? I'm using Win2D.uwp in Windows Universal App.\r\n\r\n    private async Task SaveToImage(string id, InkStroke stroke, float width, float height)\r\n    {\r\n        CanvasDevice device = CanvasDevice.GetSharedDevice();\r\n        var dpi = DisplayInformation.GetForCurrentView();\r\n\r\n        using (CanvasRenderTarget offscreen = new CanvasRenderTarget(device, width, height, dpi.LogicalDpi))\r\n        {\r\n            using (CanvasDrawingSession ds = offscreen.CreateDrawingSession())\r\n            {\r\n                ds.Clear(Colors.Transparent);\r\n                ds.DrawInk(new InkStroke[] { stroke });\r\n            }\r\n\r\n            StorageFolder folder = await GetNotesFolder();\r\n            StorageFile file = await folder.CreateFileAsync(id + \".png\", CreationCollisionOption.ReplaceExisting);\r\n\r\n            using (var output = await file.OpenAsync(FileAccessMode.ReadWrite))\r\n            {\r\n                await offscreen.SaveAsync(output, CanvasBitmapFileFormat.Png);\r\n                await output.FlushAsync();\r\n            }\r\n        }\r\n    }"},"comment":{"url":"https://api.github.com/repos/Microsoft/Win2D/issues/comments/164579117","html_url":"https://github.com/Microsoft/Win2D/issues/202#issuecomment-164579117","issue_url":"https://api.github.com/repos/Microsoft/Win2D/issues/202","id":164579117,"user":{"login":"shawnhar","id":8118468,"avatar_url":"https://avatars.githubusercontent.com/u/8118468?v=3","gravatar_id":"","url":"https://api.github.com/users/shawnhar","html_url":"https://github.com/shawnhar","followers_url":"https://api.github.com/users/shawnhar/followers","following_url":"https://api.github.com/users/shawnhar/following{/other_user}","gists_url":"https://api.github.com/users/shawnhar/gists{/gist_id}","starred_url":"https://api.github.com/users/shawnhar/starred{/owner}{/repo}","subscriptions_url":"https://api.github.com/users/shawnhar/subscriptions","organizations_url":"https://api.github.com/users/shawnhar/orgs","repos_url":"https://api.github.com/users/shawnhar/repos","events_url":"https://api.github.com/users/shawnhar/events{/privacy}","received_events_url":"https://api.github.com/users/shawnhar/received_events","type":"User","site_admin":false},"created_at":"2015-12-14T22:23:54Z","updated_at":"2015-12-14T22:23:54Z","body":"Thanks for the repro, that helped me understand what is going on.\r\n\r\nTurns out this behavior is actually by design!  It is because you are drawing the ink using the DrawAsHighlighter attribute, which causes the ink system to use a \"min\" blend mode.   Min of transparent and anything is still transparent, so nothing ever gets drawn...\r\n\r\nThe solution is either don't draw over a transparent background, or if you want the ink to be \"solid\" so it will show up even on such a background, don't use the DrawAsHighlighter attribute."}}