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66 lines
2.8 KiB
66 lines
2.8 KiB
---
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layout: page
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title: "Engine and Previews"
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description: "Camera engine and preview implementations"
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order: 7
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disqus: 1
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---
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### Engine
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CameraView can interact with the camera sensor through the old Android interface typically referred
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as `CAMERA1`, and more recently, also through the more modern interface called `CAMERA2`, for API level 21 (Lollipop).
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Being more recent, the latter received less testing and feedback. As such, to enable it, you
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are required to also set the experimental flag on: `app:cameraExperimental="true"`. On devices older
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than Lollipop, the engine will always be `Engine.CAMERA1`.
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|Engine|API Level|Info|
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|------|---------|----|
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|`Engine.CAMERA1`|All|Highly tested and reliable. Currently supports the full set of features.|
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|`Engine.CAMERA2`|API 21+|Experimental, but will be the key focus for the future. New controls might be available only for this engine.|
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### Previews
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CameraView supports different types of previews, configurable either through the `cameraPreview`
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XML attribute or programmatically with the `Preview` control class.
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All previews are supported in all conditions, regardless, for example, of the `Engine` that you
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choose.
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This parameter defaults to the OpenGL `GL_SURFACE` and it is highly recommended that you do not change this
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to use all the features available. However, experienced user might prefer a different solution.
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|Preview|Backed by|Info|
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|-------|---------|----|
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|`Preview.SURFACE`|A `SurfaceView`|Can be good for battery, but will not work well with dynamic layout changes and similar things. No support for video snapshots.|
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|`Preview.TEXTURE`|A `TextureView`|Better. Requires hardware acceleration. No support for video snapshots.|
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|`Preview.GL_SURFACE`|A `GLSurfaceView`|Recommended. Supports video snapshots. Supports [overlays](watermarks-and-overlays). Supports [real-time filters](filters).|
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The GL surface, as an extra benefit, has a much more efficient way of capturing picture snapshots,
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that avoids OOM errors, rotating the image on the fly, reading EXIF, and other horrible things belonging to v1.
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These picture snapshots will also work while taking videos.
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### XML Attributes
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```xml
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<com.otaliastudios.cameraview.CameraView
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app:cameraEngine="camera1|camera2"
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app:cameraPreview="surface|texture|glSurface"/>
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```
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### Related APIs
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The preview method should only be called once and if the `CameraView` was never added to a window,
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for example if you just created it programmatically. Otherwise, it has no effect.
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The engine method should only be called when the `CameraView` is closed. Otherwise, it has no effect.
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|Method|Description|
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|------|-----------|
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|`setPreview(Preview)`|Sets the preview implementation.|
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|`getPreview()`|Gets the current preview implementation.|
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|`setEngine(Engine)`|Sets the engine implementation.|
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|`getEngine()`|Gets the current engine implementation.|
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