java.lang.Object | |
↳ | android.graphics.SurfaceTexture |
Captures frames from an image stream as an OpenGL ES texture.
The image stream may come from either camera preview or video decode. A SurfaceTexture
may be used in place of a SurfaceHolder when specifying the output destination of a
Camera
or MediaPlayer
object. Doing so will cause all the frames from the image stream to be sent to the
SurfaceTexture object rather than to the device's display. When updateTexImage()
is
called, the contents of the texture object specified when the SurfaceTexture was created are
updated to contain the most recent image from the image stream. This may cause some frames of
the stream to be skipped.
When sampling from the texture one should first transform the texture coordinates using the
matrix queried via getTransformMatrix(float[])
. The transform matrix may change each
time updateTexImage()
is called, so it should be re-queried each time the texture image
is updated.
This matrix transforms traditional 2D OpenGL ES texture coordinate column vectors of the form (s,
t, 0, 1) where s and t are on the inclusive interval [0, 1] to the proper sampling location in
the streamed texture. This transform compensates for any properties of the image stream source
that cause it to appear different from a traditional OpenGL ES texture. For example, sampling
from the bottom left corner of the image can be accomplished by transforming the column vector
(0, 0, 0, 1) using the queried matrix, while sampling from the top right corner of the image can
be done by transforming (1, 1, 0, 1).
The texture object uses the GL_TEXTURE_EXTERNAL_OES texture target, which is defined by the GL_OES_EGL_image_external OpenGL ES extension. This limits how the texture may be used. Each time the texture is bound it must be bound to the GL_TEXTURE_EXTERNAL_OES target rather than the GL_TEXTURE_2D target. Additionally, any OpenGL ES 2.0 shader that samples from the texture must declare its use of this extension using, for example, an "#extension GL_OES_EGL_image_external : require" directive. Such shaders must also access the texture using the samplerExternalOES GLSL sampler type.
SurfaceTexture objects may be created on any thread. updateTexImage()
may only be
called on the thread with the OpenGL ES context that contains the texture object. The
frame-available callback is called on an arbitrary thread, so unless special care is taken updateTexImage()
should not be called directly from the callback.
Nested Classes | |||||||||||
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SurfaceTexture.OnFrameAvailableListener | Callback interface for being notified that a new stream frame is available. | ||||||||||
SurfaceTexture.OutOfResourcesException |
This class was deprecated
in API level 19.
No longer thrown. Surface.OutOfResourcesException
is used instead.
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Public Constructors | |||||||||||
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Construct a new SurfaceTexture to stream images to a given OpenGL texture.
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Construct a new SurfaceTexture to stream images to a given OpenGL texture.
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Public Methods | |||||||||||
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Attach the SurfaceTexture to the OpenGL ES context that is current on the calling thread.
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Detach the SurfaceTexture from the OpenGL ES context that owns the OpenGL ES texture object.
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Retrieve the timestamp associated with the texture image set by the most recent call to
updateTexImage.
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Retrieve the 4x4 texture coordinate transform matrix associated with the texture image set by
the most recent call to updateTexImage.
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release() frees all the buffers and puts the SurfaceTexture into the
'abandoned' state.
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Releases the the texture content.
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Set the default size of the image buffers.
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Register a callback to be invoked when a new image frame becomes available to the
SurfaceTexture.
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Register a callback to be invoked when a new image frame becomes available to the
SurfaceTexture.
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Update the texture image to the most recent frame from the image stream.
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Protected Methods | |||||||||||
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Invoked when the garbage collector has detected that this instance is no longer reachable.
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[Expand]
Inherited Methods | |||||||||||
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From class
java.lang.Object
|
Construct a new SurfaceTexture to stream images to a given OpenGL texture.
texName | the OpenGL texture object name (e.g. generated via glGenTextures) |
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If the SurfaceTexture cannot be created. |
Construct a new SurfaceTexture to stream images to a given OpenGL texture.
In single buffered mode the application is responsible for serializing access to the image
content buffer. Each time the image content is to be updated, the
releaseTexImage()
method must be called before the image content producer takes
ownership of the buffer. For example, when producing image content with the NDK
ANativeWindow_lock and ANativeWindow_unlockAndPost functions, releaseTexImage()
must be called before each ANativeWindow_lock, or that call will fail. When producing
image content with OpenGL ES, releaseTexImage()
must be called before the first
OpenGL ES function call each frame.
texName | the OpenGL texture object name (e.g. generated via glGenTextures) |
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singleBufferMode | whether the SurfaceTexture will be in single buffered mode. |
If the SurfaceTexture cannot be created. |
Attach the SurfaceTexture to the OpenGL ES context that is current on the calling thread. A
new OpenGL ES texture object is created and populated with the SurfaceTexture image frame
that was current at the time of the last call to detachFromGLContext()
. This new
texture is bound to the GL_TEXTURE_EXTERNAL_OES texture target.
This can be used to access the SurfaceTexture image contents from multiple OpenGL ES
contexts. Note, however, that the image contents are only accessible from one OpenGL ES
context at a time.
texName | The name of the OpenGL ES texture that will be created. This texture name must be unusued in the OpenGL ES context that is current on the calling thread. |
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Detach the SurfaceTexture from the OpenGL ES context that owns the OpenGL ES texture object.
This call must be made with the OpenGL ES context current on the calling thread. The OpenGL
ES texture object will be deleted as a result of this call. After calling this method all
calls to updateTexImage()
will throw an IllegalStateException
until
a successful call to attachToGLContext(int)
is made.
This can be used to access the SurfaceTexture image contents from multiple OpenGL ES
contexts. Note, however, that the image contents are only accessible from one OpenGL ES
context at a time.
Retrieve the timestamp associated with the texture image set by the most recent call to updateTexImage. This timestamp is in nanoseconds, and is normally monotonically increasing. The timestamp should be unaffected by time-of-day adjustments, and for a camera should be strictly monotonic but for a MediaPlayer may be reset when the position is set. The specific meaning and zero point of the timestamp depends on the source providing images to the SurfaceTexture. Unless otherwise specified by the image source, timestamps cannot generally be compared across SurfaceTexture instances, or across multiple program invocations. It is mostly useful for determining time offsets between subsequent frames.
Retrieve the 4x4 texture coordinate transform matrix associated with the texture image set by the most recent call to updateTexImage. This transform matrix maps 2D homogeneous texture coordinates of the form (s, t, 0, 1) with s and t in the inclusive range [0, 1] to the texture coordinate that should be used to sample that location from the texture. Sampling the texture outside of the range of this transform is undefined. The matrix is stored in column-major order so that it may be passed directly to OpenGL ES via the glLoadMatrixf or glUniformMatrix4fv functions.
mtx | the array into which the 4x4 matrix will be stored. The array must have exactly 16 elements. |
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release() frees all the buffers and puts the SurfaceTexture into the 'abandoned' state. Once put in this state the SurfaceTexture can never leave it. When in the 'abandoned' state, all methods of the IGraphicBufferProducer interface will fail with the NO_INIT error. Note that while calling this method causes all the buffers to be freed from the perspective of the the SurfaceTexture, if there are additional references on the buffers (e.g. if a buffer is referenced by a client or by OpenGL ES as a texture) then those buffer will remain allocated. Always call this method when you are done with SurfaceTexture. Failing to do so may delay resource deallocation for a significant amount of time.
Releases the the texture content. This is needed in single buffered mode to allow the image
content producer to take ownership of the image buffer.
For more information see SurfaceTexture(int, boolean)
.
Set the default size of the image buffers. The image producer may override the buffer size,
in which case the producer-set buffer size will be used, not the default size set by this
method. Both video and camera based image producers do override the size. This method may
be used to set the image size when producing images with Canvas
(via
lockCanvas(Rect)
), or OpenGL ES (via an EGLSurface).
The new default buffer size will take effect the next time the image producer requests a
buffer to fill. For Canvas
this will be the next time lockCanvas(Rect)
is called. For OpenGL ES, the EGLSurface should be
destroyed (via eglDestroySurface), made not-current (via eglMakeCurrent), and then recreated
(via eglCreateWindowSurface) to ensure that the new default size has taken effect.
The width and height parameters must be no greater than the minimum of
GL_MAX_VIEWPORT_DIMS and GL_MAX_TEXTURE_SIZE (see
glGetIntegerv
).
An error due to invalid dimensions might not be reported until
updateTexImage() is called.
Register a callback to be invoked when a new image frame becomes available to the SurfaceTexture.
If a handler is specified, the callback will be invoked on that handler's thread.
If no handler is specified, then the callback may be called on an arbitrary thread,
so it is not safe to call updateTexImage()
without first binding the OpenGL ES
context to the thread invoking the callback.
listener | The listener to use, or null to remove the listener. |
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handler | The handler on which the listener should be invoked, or null to use an arbitrary thread. |
Register a callback to be invoked when a new image frame becomes available to the SurfaceTexture.
The callback may be called on an arbitrary thread, so it is not
safe to call updateTexImage()
without first binding the OpenGL ES context to the
thread invoking the callback.
listener | The listener to use, or null to remove the listener. |
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Update the texture image to the most recent frame from the image stream. This may only be called while the OpenGL ES context that owns the texture is current on the calling thread. It will implicitly bind its texture to the GL_TEXTURE_EXTERNAL_OES texture target.
Invoked when the garbage collector has detected that this instance is no longer reachable. The default implementation does nothing, but this method can be overridden to free resources.
Note that objects that override finalize
are significantly more expensive than
objects that don't. Finalizers may be run a long time after the object is no longer
reachable, depending on memory pressure, so it's a bad idea to rely on them for cleanup.
Note also that finalizers are run on a single VM-wide finalizer thread,
so doing blocking work in a finalizer is a bad idea. A finalizer is usually only necessary
for a class that has a native peer and needs to call a native method to destroy that peer.
Even then, it's better to provide an explicit close
method (and implement
Closeable
), and insist that callers manually dispose of instances. This
works well for something like files, but less well for something like a BigInteger
where typical calling code would have to deal with lots of temporaries. Unfortunately,
code that creates lots of temporaries is the worst kind of code from the point of view of
the single finalizer thread.
If you must use finalizers, consider at least providing your own
ReferenceQueue
and having your own thread process that queue.
Unlike constructors, finalizers are not automatically chained. You are responsible for
calling super.finalize()
yourself.
Uncaught exceptions thrown by finalizers are ignored and do not terminate the finalizer thread. See Effective Java Item 7, "Avoid finalizers" for more.
Throwable |
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