Embedding and managing images and other media content in a mobile application is always challenging. The processes of downloading a media file from the web, storing it on the device, and then displaying it to the user are surprisingly and often frustratingly complex from a coding perspective. In addition, you probably want to add code that enables reusing images rather than downloading it every time, but you have to be smart about it to avoid clogging the precious storage space on your customer’s device. Furthermore, your design probably requires that images be displayed in different sizes and DPRs in different devices, but creating and maintaining multiple versions of every image manually is virtually impossible.
In this article, I’ll demonstrate how you can handle all these tasks with just a few simple lines of code using the new Swift-based Cloudinary iOS SDK.
Cloudinary provides a cloud-based service to handle upload, storage, manipulation, and administration of images and other media content. The simple interface, combined with an extensive set of features, is particularly useful to mobile developers: it alleviates the burden of resource management, letting developers focus on their core application’s features.
The latest version of the Cloudinary iOS SDK has been completely re-written in Swift and was developed with the following goals:
- Adopt Swift’s design paradigms
- Support both Swift 2.3 and Swift 3.0
- Support developers still using Objective-C
- Maintain a familiar API to ease the migration from the previous version of the Cloudinary iOS SDK
First, make sure you have a Cloudinary account. If you don’t have one yet, you can register for a free account.
After you have an account, get the Cloudinary iOS SDK code either using Cocoapods or directly from the github repository.
Install from Cocoapods
Add a dependency on Cloudinary in your Podfile:
Then, run the command:
$ pod install
After installing, follow the Configuration instructions in the SDK readme to set up your environment to work with Cloudinary.
Here’s a quick sample of configuring and initiating the Cloudinary SDK. All following code samples will assume this configuration is in place.
One of those big challenges we mentioned at the beginning of this article is the huge quantity of different screen sizes and resolutions you need to take into account. You can set up your app to display completely different designs depending on the screen real estate available, but if your different designs require displaying images at different sizes and scales, then preparing and maintaining multiple versions of every graphic quickly becomes unmanageable. And if you also need to resize user-generated content on-the-fly depending on display size, then you absolutely must have an automated solution.
Luckily, it’s easy to make these adjustments on-the-fly using Cloudinary transformations with the iOS SDK.
Cloudinary transformations enable you to crop, scale, rotate, add shadows, outlines, backgrounds, and select from a huge set of artistic filters and special effects, simply by setting method values.
And of-course in addition to using these transformations to make your own app design responsive, you can also pass on all of these manipulation capabilities to your users as photo editing features in your app.
As a (major) added bonus, Cloudinary performs a number of automatic optimizations whenever it generates a transformed image. And beyond these, you can also take advantage of special optimization transformations like auto-quality and auto-format to ensure that every image you deliver uses minimum bandwidth while delivering the needed visual quality. For more details, see Image Optimization.
There is also a nice set of video-specific transcoding and transformation options available, including HTTP Live Streaming (HLS) output. The HLS transcoding feature enables you to automatically generate multiple representations at the quality and sizes you need in order to deliver video in the required HLS adaptive bitrate streaming format.
Note: If your iOS app delivers video over cellular networks, and the video exceeds either 10 minutes overall or more than 5 MB of data in a five-minute period, you are required to deliver it using HTTP Live Streaming.
Transformations are represented with the
CLDTransformation class. Here are a couple of examples. The first scales an image to a width of 500px. The second applies a sepia effect and rounds the corners of an image to a circle or ellipse.
To generate the URL for an image or video asset:
To generate a URL with the transformation we created above:
The entire process can also be combined in a one liner:
So now you know how to generate cool looking, optimized images from Cloudinary, but you still need to display them to the user.
The Cloudinary SDK provides extensions to iOS UI elements, which make the presentation of an image easy. These extensions provide a single API that automatically fetches and downloads an image in the background, and sets it to be displayed in the UI.
Extensions are available for:
In the following example, an image that was uploaded with the public id:
public_id and a predefined transformation stored in
transformation is assigned to the UIImageView variable named
For a complete code example, visit our sample application.
As we explained above, the Cloudinary SDK automatically fetches and downloads your media resources for you as part of the delivery process, but if you just want to download without displaying, or you want to download separately for any other reason, here are the basics of what normally happens behind the scenes:
First, create a downloader instance:
Then fetch an image or video. Below, we use the image URL (
imageURL) we created earlier.
To avoid blocking the application during the download, network access is performed asynchronously in a separate thread. Thus you must provide a callback closure to handle the results of the action.
Notice the callback structure: the last parameter is a closure that receives the downloaded image or an error object. In Swift ,this pattern is called a trailing closure. Swift provides syntactic sugar for trailing closures by allowing the parameter to be provided outside the parameter parentheses. Sweet!
Your users want to show the world their latest meal? With the Cloudinary SDK, uploading is a breeze!
The SDK enables you to upload an image from several sources:
- The image data, provided by a UI element or from a source, such as a UIImagePickerController
- A URI pointing to an image file on the user’s device
- An external URL pointing to an image available on the web
In addition to specifying the media file in your upload call, you also need to provide an unsigned upload preset. An unsigned upload preset is a Cloudinary feature that allows your users to upload directly to your Cloudinary account without having to sign the request. This feature is popular among mobile app developers as it provides close control over the uploaded material without requiring the storage of sensitive credentials on the mobile application.
Unsigned upload presets inherently have some protective limitations. For example, users can’t overwrite existing images in your account. You can also set additional limitations when you define your upload preset, such as limiting the file size or type of files they can upload. You create and configure the unsigned upload preset in the Cloudinary console.
After you create the upload preset, you specify it in your upload code as follows:
The above shows the most basic upload example, but there are also a large number of optional upload parameters you can set in the upload call.
The result of the upload API call is a
CLDUploadResult object that provides information about the uploaded image, as well as the public ID of the image and its URL.
Cloudinary’s iOS implementation also puts emphasis on avoiding redundant downloads through caching.
The first time the
fetchImage() method is called for a particular resource, Cloudinary stores it in the device cache. Each subsequent time that the
fetchImage() method is called, it first tries to find the image in the local cache, and retrieves it from the cache if it was found. If it was not found in the cache, the image is downloaded from Cloudinary, stored in the cache and then returned to the caller. The device cache used for this purpose has a predefined maximum memory and disk space, that is cleaned out in FIFO order to make room for the latest images.
The Cloudinary iOS SDK was developed with a focus on the challenges that iOS developers face, especially uploading and downloading, and device sizing issues. Manipulation features enable you to easily deliver images in different sizes for different devices on-the-fly as well as treating you to a great toolbox of photo manipulation features that you can apply to your images and/or pass on to your users. HLS transcoding enables you to deliver video at the quality and size that best fits each user’s device and network connection, and to answer iOS requirements. Optimization and caching features help you to preserve precious bytes and make the most of the available bandwidth with every delivered resource.
And all of this in a nice and neat Swift package that integrates seamlessly with your own Swift or Objective-C code.
Ready to swoop right in? If you don’t have a Cloudinary account yet, take a minute to sign up for a free one, and spread your wings!