Understanding @3x Artwork for iPhone 6+ Devices

Introduction

As a developer, creating apps that cater to various screen sizes and resolutions can be a daunting task. One aspect that is often overlooked is the @3x artwork requirement for iOS devices like the iPhone 6+. In this article, we will delve into the world of @3x artwork, exploring its purpose, how it relates to screen resolution, and how to implement it in your app.

Background

The concept of @2x, @3x, and @4x artwork originated from Apple’s efforts to reduce battery consumption by reducing the number of images that need to be redrawn. By providing alternative resolutions for the same image, developers can ensure their app adapts seamlessly to different screen sizes without compromising performance.

Screen Resolution and Coordinate Space

The iPhone 6+ has a unique coordinate space, which is different from other devices. To understand this concept better, let’s break it down:

The standard coordinate space (x, y) for most screens is measured in pixels.
However, the iPhone 6+’s coordinate system uses points as its unit of measurement.

For example, if you have an image with a width and height of width x height points, you would need to convert this value to pixels when working with it. The conversion factor depends on the device’s screen resolution.

@2x, @3x, and @4x Artwork

When creating artwork for iOS devices, developers often create multiple versions with different resolutions:

@2x: Resolved at 2 times the standard coordinate space (2x) to accommodate smaller screens.
@3x: Resolved at 3 times the standard coordinate space (3x) to fit larger screens like the iPhone 6+.
@4x: Resolved at 4 times the standard coordinate space (4x) for even larger screens.

Scaling Up Assets

When scaling up an asset, it’s essential to consider both the device’s screen resolution and the type of artwork being created. For @3x assets, Apple recommends using the following formula:

image_size_x = image_size_x_original \* 3 / 2
image_size_y = image_size_y_original \* 3 / 2

This means that if you have an original image_size_x x image_size_y pixels asset, your @3x version should be:

image_size_x_new = image_size_x_original \* (3/2)
image_size_y_new = image_size_y_original \* (3/2)

Apple Documentation and the 1.15 Factor

The Apple documentation mentions a scale_factor of 1.15, which is used to adjust the artwork size for the iPhone 6+’s coordinate space. However, as the provided Stack Overflow question points out, this factor is not needed when creating @3x assets.

Implementing @3x Artwork in Your App

To implement @3x artwork in your app:

Create your original @2x asset(s) for smaller screens.
Use the scaling formula mentioned earlier to create your @3x asset(s).
Name your @3x asset(s) with the .tiff extension (e.g., button.png.tiff).
In your app’s assets folder, include both the @2x and @3x versions of each image.
Use Xcode to configure your app’s UI elements to use the correct artwork for different screen sizes.

Conclusion

In conclusion, creating @3x artwork for iOS devices like the iPhone 6+ is a matter of scaling up your original assets by a factor of 3/2 and naming them correctly. While Apple documentation mentions a scale_factor of 1.15, this factor is unnecessary when working with @3x assets.

By understanding the concept of @3x artwork and implementing it correctly in your app, you can ensure that your app adapts seamlessly to different screen sizes without compromising performance or battery life.

Last modified on 2025-01-23