5.2 KiB
How photos are generated
Overview of how and when versions of photos are generated
By default, when a photo is uploaded there are two versions of that photo which are stored. The original version (pathOriginal) and a slightly lower resolution version (pathBase).
The API is capable of returning URLs for any size version of every photo. This is acheived by passing in a parameter named returnSizes to the GET Photos and GET Photo APIs. This ensures that the response for the photo(s) will include a URL for the size(s) you specify. Here is an example.
curl "http://current.openphoto.me/photo/63.json?returnSizes=123x123"
This call returns the following response.
{
"code" : 200,
"message" : "Photo 63",
"result" : {
"appId" : "current.openphoto.me",
"creativeCommons" : "BY-NC",
"dateTaken" : "1313010850",
"dateTakenDay" : "10",
"dateTakenMonth" : "08",
"dateTakenYear" : "2011",
"dateUploaded" : "1313010853",
"dateUploadedDay" : "10",
"dateUploadedMonth" : "08",
"dateUploadedYear" : "2011",
"description" : "",
"exifCameraMake" : "",
"exifCameraModel" : "",
"hash" : "20d64642f09befc4004c22269e698e6e43475963",
"height" : "1936",
"host" : "opmecurrent.s3.amazonaws.com",
"id" : "63",
"latitude" : "",
"longitude" : "",
"path123x123" : "http://current.openphoto.me/photo/63/create/1a7f0/123x123.jpg",
"path200x200" : "http://opmecurrent.s3.amazonaws.com/custom/201108/1313010849-opmeTbrBki_200x200.jpg",
"pathBase" : "/base/201108/1313010849-opmeTbrBki.jpg",
"pathOriginal" : "/original/201108/1313010849-opmeTbrBki.jpg",
"permission" : "1",
"size" : "1513",
"status" : "1",
"tags" : [ ],
"title" : "Gulf Shores, AL",
"views" : "0",
"width" : "2592"
}
}
The most important keys in the response are path123x123 and path200x200. Either of these URLs will correctly render the photo in the respective size. Notice, however, that the path123x123 hostname is different from path200x200. This is important because this implies that a 123x123 version of the photo doesn't exist and the API host needs to generate it. The following url will generate the correct version of the photo, store it to the proper file system, saves it to the database and returns it with a content-type of image/jpeg.
http://current.openphoto.me/photo/63/create/1a7f0/123x123.jpg
It's important to realize that the photo isn't generated and stored until this URL is called. This typically happens when the browser tries to display this photo. Once that has happened then the 123x123 version exists both in the database and file system and calling the same API again returns a different URL for path123x123.
{
"code" : 200,
"message" : "Photo 63",
"result" : {
"appId" : "current.openphoto.me",
"creativeCommons" : "BY-NC",
"dateTaken" : "1313010850",
"dateTakenDay" : "10",
"dateTakenMonth" : "08",
"dateTakenYear" : "2011",
"dateUploaded" : "1313010853",
"dateUploadedDay" : "10",
"dateUploadedMonth" : "08",
"dateUploadedYear" : "2011",
"description" : "",
"exifCameraMake" : "",
"exifCameraModel" : "",
"hash" : "20d64642f09befc4004c22269e698e6e43475963",
"height" : "1936",
"host" : "opmecurrent.s3.amazonaws.com",
"id" : "63",
"latitude" : "",
"longitude" : "",
"path123x123" : "http://opmecurrent.s3.amazonaws.com/custom/201108/1313010849-opmeTbrBki_123x123.jpg",
"path200x200" : "http://opmecurrent.s3.amazonaws.com/custom/201108/1313010849-opmeTbrBki_200x200.jpg",
"pathBase" : "/base/201108/1313010849-opmeTbrBki.jpg",
"pathOriginal" : "/original/201108/1313010849-opmeTbrBki.jpg",
"permission" : "1",
"size" : "1513",
"status" : "1",
"tags" : [ ],
"title" : "Gulf Shores, AL",
"views" : "0",
"width" : "2592"
}
}
The URL for path123x123 now points to a static resource.
You can specify multiple sizes for the returnSizes delimited by commas.
curl "http://current.openphoto.me/photo/63.json?returnSizes=123x123,300x300xBW"
Understanding options for returnSizes
The returnSizes parameter takes values in the form of WxH[[xA]xB] which means it starts with a numeric width and height. The most simple form is limited to specifying just a width and height. This looks like 200x200 or 125x300.
Additional options include CR and BW. CR tells the API to crop the photo to be exactly width by height. It does a center crop and minimizes the portion of the photo that is cropped. BW applies a greyscale filter to the photo. 100x100xCRxBW means the photo will have a key of path100x100xCRxBW and will be exactly 100 by 100, cropped and greyscale.
For more information on the returnSizes parameter see our documentation on returnSizes.