Image Targets represent images that Vuforia Engine can detect and track. Unlike traditional fiducial markers, data matrix codes, and QR codes, Image Targets do not need special black and white regions or codes to be recognized. The Engine detects and tracks the features that are naturally found in the image itself by comparing these natural features against a known target resource database. Once the Image Target is detected, Vuforia Engine will track the image as long as it is at least partially in the camera’s field of view.
Common uses of Image Targets include recognizing and augmenting printed media and product packaging for marketing campaigns, gaming, and visualizing products in the environment where the product was intended to be used.
Image targets can be created with the Vuforia Target Manager using JPG or PNG images in RGB or grayscale. The size of the input images must 2 MB or less. Features extracted from these images are stored in a database, which can then be downloaded and packaged together with the application. The database can then be used by Vuforia Engine for runtime comparisons.
Image Targets should be viewed under moderately bright and diffused lighting. The surface of the image should be evenly lit.
Working with Image Targets
There are two phases to developing with Image Targets. You first need to design your target images and then upload them to the Vuforia Target Manager for processing and evaluation.
Designing Target Images
Image Targets can use any planar image that provides sufficient detail to be detected by Vuforia Engine. The following articles will help you select appropriate target surfaces and provide guidelines on how to design and evaluate target images.
See: Optimizing Target Detection and Tracking Stability
Uploading and Managing Image Targets
Image targets can be incorporated into your apps using either an embedded Device Database or an online Cloud Database. The Vuforia Target Manager creates image targets. It processes images to generate both data and visual representations of the target features. It also provides the target's expected detection and tracking performance rating. Image targets can also be created for use in cloud recognition databases.
The Image Targets sample shows you how to implement and configure Image Targets in an application. You can customize these samples with your own targets and content.
The Cloud Recognition sample shows how to use Image Targets with the Vuforia Cloud Recognition service and how to develop apps that execute and respond to queries to the service.
Using Extended Tracking with Image Targets
Extended Tracking improves tracking robustness by using features of the environment surrounding the target. It enables you to use larger models and to place them farther away from the face of the target. Use Extended Tracking when your target will be staged in a stable environment and won't be moved by the user. Moving the target or changing its environment when Extended Tracking is activated can corrupt tracking.
See: Extended Tracking
Using Virtual Buttons with Image Targets
Virtual Buttons enable you to know when a specific area of the target image has been covered by the user. They provide a way to make Image Targets interactive. The following articles explain how to define and configure Virtual Buttons and how to add them to an Image Target.
See: How To Implement Virtual Buttons
When the image is being uploaded to the Target Manager, we recommend scaling the image to be uploaded to 320 pixels or larger width. During the resizing process, anti-aliasing is performed on the uploaded image. This action is perfectly acceptable for photos; however, this action may not always be desirable.
To avoid experiencing the anti-aliasing impact, you can ensure that the uploaded image is at least 320 pixels in width. Stretching and softening in the image due to a server-side scaling step results in a lower feature count and worse local contrast in the image. This may not be visible immediately, but such targets can result in poor target detection and tracking.
The parameters of an Image Target are defined in the Target Manager, according to the following specifications. The Virtual Buttons parameter can be added to the config.xml file returned by the Target Manager with the target's dataset.
Note: The size of the image target can be changed at runtime. This offers flexibility in defining or updating the scale of the target in your 3D scene.
Note: Developers looking to use image targets in combination with Positional Device Tracker should specify the target size in meters.
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