ImageWriter

close

open fun close(): Unit

Free up all the resources associated with this ImageWriter.

After calling this method, this ImageWriter cannot be used. Calling any methods on this ImageWriter and Images previously provided by dequeueInputImage() will result in an IllegalStateException, and attempting to write into ByteBuffers returned by an earlier Plane#getBuffer call will have undefined behavior.

dequeueInputImage

open fun dequeueInputImage(): Image!

Dequeue the next available input Image for the application to produce data into.

This method requests a new input Image from ImageWriter. The application owns this Image after this call. Once the application fills the Image data, it is expected to return this Image back to ImageWriter for downstream consumer components (e.g. android.hardware.camera2.CameraDevice) to consume. The Image can be returned to ImageWriter via queueInputImage or Image#close().

This call will block if all available input images have been queued by the application and the downstream consumer has not yet consumed any. When an Image is consumed by the downstream consumer and released, an OnImageReleasedListener#onImageReleased callback will be fired, which indicates that there is one input Image available. For non- PRIVATE formats ( ImageWriter#getFormat() != ImageFormat#PRIVATE), it is recommended to dequeue the next Image only after this callback is fired, in the steady state.

If the format of ImageWriter is PRIVATE ( ImageWriter#getFormat() == ImageFormat#PRIVATE), the image buffer is accessible to the application only through the hardware buffer obtained through Image#getHardwareBuffer(). (On Android versions prior to P, dequeueing private buffers will cause an IllegalStateException to be thrown). Alternatively, the application can acquire images from some other component (e.g. an ImageReader), and queue them directly to this ImageWriter via the queueInputImage() method.

getDataSpace

open fun getDataSpace(): Int

Get the ImageWriter dataspace.

Use this function if the ImageWriter instance is created by builder pattern ImageWriter.Builder and Builder#setDataSpace.

getFormat

open fun getFormat(): Int

Get the ImageWriter format.

This format may be different than the Image format returned by Image#getFormat(). However, if the ImageWriter format is PRIVATE, calling dequeueInputImage() will result in an IllegalStateException.

getHardwareBufferFormat

open fun getHardwareBufferFormat(): Int

Get the ImageWriter hardwareBuffer format.

Use this function if the ImageWriter instance is created by builder pattern ImageWriter.Builder and using Builder#setHardwareBufferFormat and Builder#setDataSpace.

getHeight

open fun getHeight(): Int

The height of Images, in pixels.

If Builder#setWidthAndHeight is not called, the default height of the Image depends on the Surface provided by customer end-point.

getMaxImages

open fun getMaxImages(): Int

Maximum number of Images that can be dequeued from the ImageWriter simultaneously (for example, with dequeueInputImage()).

An Image is considered dequeued after it's returned by dequeueInputImage() from ImageWriter, and until the Image is sent back to ImageWriter via queueInputImage, or Image#close().

Attempting to dequeue more than maxImages concurrently will result in the dequeueInputImage() function throwing an IllegalStateException.

getUsage

open fun getUsage(): Long

Get the ImageWriter usage flag.

It is not recommended to use this function if Builder#setUsage is not called. Invalid usage value will be returned if so.

getWidth

open fun getWidth(): Int

The width of Images, in pixels.

If Builder#setWidthAndHeight is not called, the default width of the Image depends on the Surface provided by customer end-point.

newInstance

open static fun newInstance(
    surface: Surface, 
    maxImages: Int
): ImageWriter

Create a new ImageWriter.

The maxImages parameter determines the maximum number of Image objects that can be be dequeued from the ImageWriter simultaneously. Requesting more buffers will use up more memory, so it is important to use only the minimum number necessary.

The input Image size and format depend on the Surface that is provided by the downstream consumer end-point.

newInstance

open static fun newInstance(
    surface: Surface, 
    maxImages: Int, 
    format: Int
): ImageWriter

Create a new ImageWriter with given number of max Images and format.

The maxImages parameter determines the maximum number of Image objects that can be be dequeued from the ImageWriter simultaneously. Requesting more buffers will use up more memory, so it is important to use only the minimum number necessary.

The format specifies the image format of this ImageWriter. The format from the surface will be overridden with this format. For example, if the surface is obtained from a android.graphics.SurfaceTexture, the default format may be PixelFormat#RGBA_8888. If the application creates an ImageWriter with this surface and ImageFormat#PRIVATE, this ImageWriter will be able to operate with ImageFormat#PRIVATE Images.

Note that the consumer end-point may or may not be able to support Images with different format, for such case, the application should only use this method if the consumer is able to consume such images.

The input Image size depends on the Surface that is provided by the downstream consumer end-point.

queueInputImage

open fun queueInputImage(image: Image!): Unit

Queue an input Image back to ImageWriter for the downstream consumer to access.

The input Image could be from ImageReader (acquired via ImageReader#acquireNextImage or ImageReader#acquireLatestImage), or from this ImageWriter (acquired via dequeueInputImage). In the former case, the Image data will be moved to this ImageWriter. Note that the Image properties (size, format, strides, etc.) must be the same as the properties of the images dequeued from this ImageWriter. In the latter case, the application has filled the input image with data. This method then passes the filled buffer to the downstream consumer. In both cases, it's up to the caller to ensure that the Image timestamp (in nanoseconds) is correctly set, as the downstream component may want to use it to indicate the Image data capture time.

After this method is called and the downstream consumer consumes and releases the Image, an OnImageReleasedListener#onImageReleased callback will fire. The application can use this callback to avoid sending Images faster than the downstream consumer processing rate in steady state.

Passing in an Image from some other component (e.g. an ImageReader) requires a free input Image from this ImageWriter as the destination. In this case, this call will block, as dequeueInputImage does, if there are no free Images available. To avoid blocking, the application should ensure that there is at least one free Image available in this ImageWriter before calling this method.

After this call, the input Image is no longer valid for further access, as if the Image is closed. Attempting to access the ByteBuffers returned by an earlier Plane#getBuffer call will result in an IllegalStateException.

setOnImageReleasedListener

open fun setOnImageReleasedListener(
    listener: ImageWriter.OnImageReleasedListener!, 
    handler: Handler!
): Unit

Register a listener to be invoked when an input Image is returned to the ImageWriter.

finalize

protected open fun finalize(): Unit