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ImageAnalysis

public final class ImageAnalysis
extends UseCase

java.lang.Object
   ↳ androidx.camera.core.UseCase
     ↳ androidx.camera.core.ImageAnalysis

A use case providing CPU accessible images for an app to perform image analysis on.

ImageAnalysis acquires images from the camera via an ImageReader. Each image is provided to an ImageAnalysis.Analyzer function which can be implemented by application code, where it can access image data for application analysis via an ImageProxy.

The application is responsible for calling ImageProxy.close() to close the image. Failing to close the image will cause future images to be stalled or dropped depending on the ImageAnalysis.BackpressureStrategy.

Summary

Nested classes

interface ImageAnalysis.Analyzer

Interface for analyzing images. 

@interface ImageAnalysis.BackpressureStrategy

How to apply backpressure to the source producing images for analysis. 

class ImageAnalysis.Builder

Builder for a ImageAnalysis. 

Public methods

void clearAnalyzer()

Removes a previously set analyzer.

void setAnalyzer(Executor executor, ImageAnalysis.Analyzer analyzer)

Sets an analyzer to receive and analyze images.

void setTargetRotation(int rotation)

Sets the target rotation.

String toString()

Inherited methods

Public methods

clearAnalyzer

public void clearAnalyzer ()

Removes a previously set analyzer.

This will stop data from streaming to the ImageAnalysis.

setAnalyzer

public void setAnalyzer (Executor executor, 
                ImageAnalysis.Analyzer analyzer)

Sets an analyzer to receive and analyze images.

Setting an analyzer will signal to the camera that it should begin sending data. The stream of data can be stopped by calling clearAnalyzer().

Applications can process or copy the image by implementing the ImageAnalysis.Analyzer. If frames should be skipped (no analysis), the analyzer function should return, instead of disconnecting the analyzer function completely.

Setting an analyzer function replaces any previous analyzer. Only one analyzer can be set at any time.

Parameters
executor Executor: The executor in which the ImageAnalysis.Analyzer.analyze(ImageProxy, int) will be run.
analyzer ImageAnalysis.Analyzer: of the images.

setTargetRotation

public void setTargetRotation (int rotation)

Sets the target rotation.

This informs the use case so it can adjust the rotation value sent to ImageAnalysis.Analyzer.analyze(ImageProxy, int) which provides rotation information to the analysis method. The rotation parameter sent to the analyzer will be the rotation, which if applied to the output image, will make the image match target rotation specified here.

While rotation can also be set via ImageAnalysis.Builder.setTargetRotation(int), using setTargetRotation(int) allows the target rotation to be set dynamically.

In general, it is best to use an OrientationEventListener to set the target rotation. This way, the rotation output to the Analyzer will indicate which way is down for a given image. This is important since display orientation may be locked by device default, user setting, or app configuration, and some devices may not transition to a reverse-portrait display orientation. In these cases, use setTargetRotation(int) to set target rotation dynamically according to the OrientationEventListener, without re-creating the use case. Note the OrientationEventListener output of degrees in the range [0..359] should be converted to a surface rotation, i.e. one of Surface.ROTATION_0, Surface.ROTATION_90, Surface.ROTATION_180, or Surface.ROTATION_270.

If not set here or by configuration, the target rotation will default to the value of Display.getRotation() of the default display at the time the use case is created.

Parameters
rotation int: Target rotation of the output image, expressed as one of Surface.ROTATION_0, Surface.ROTATION_90, Surface.ROTATION_180, or Surface.ROTATION_270.

toString

public String toString ()

Returns
String