SurfaceTexture
public
class
SurfaceTexture
extends Object
| 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
Surface created from a SurfaceTexture can be used as an output
destination for the android.hardware.camera2, MediaCodec,
MediaPlayer, and Allocation APIs.
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.
A SurfaceTexture may also be used in place of a SurfaceHolder when specifying the output
destination of the older Camera API. 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.
A typical pattern is to use SurfaceTexture to render frames to a TextureView; however,
a TextureView is not required for using the texture object. The texture object may be used
as part of an OpenGL ES shader.
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.
Summary
Nested classes | |
|---|---|
interface |
SurfaceTexture.OnFrameAvailableListener
Callback interface for being notified that a new stream frame is available. |
class |
SurfaceTexture.OutOfResourcesException
This class was deprecated
in API level 19.
No longer thrown. |
Public constructors | |
|---|---|
SurfaceTexture(int texName)
Construct a new SurfaceTexture to stream images to a given OpenGL texture. |
|
SurfaceTexture(int texName, boolean singleBufferMode)
Construct a new SurfaceTexture to stream images to a given OpenGL texture. |
|
SurfaceTexture(boolean singleBufferMode)
Construct a new SurfaceTexture to stream images to a given OpenGL texture. |
|
Public methods | |
|---|---|
void
|
attachToGLContext(int texName)
Attach the SurfaceTexture to the OpenGL ES context that is current on the calling thread. |
void
|
detachFromGLContext()
Detach the SurfaceTexture from the OpenGL ES context that owns the OpenGL ES texture object. |
int
|
getDataSpace()
Retrieve the dataspace associated with the texture image. |
long
|
getTimestamp()
Retrieve the timestamp associated with the texture image set by the most recent call to
|
void
|
getTransformMatrix(float[] mtx)
Retrieve the 4x4 texture coordinate transform matrix associated with the texture image set by
the most recent call to |
boolean
|
isReleased()
Returns |
void
|
release()
|
void
|
releaseTexImage()
Releases the texture content. |
void
|
setDefaultBufferSize(int width, int height)
Set the default size of the image buffers. |
void
|
setOnFrameAvailableListener(SurfaceTexture.OnFrameAvailableListener listener, Handler handler)
Register a callback to be invoked when a new image frame becomes available to the SurfaceTexture. |
void
|
setOnFrameAvailableListener(SurfaceTexture.OnFrameAvailableListener listener)
Register a callback to be invoked when a new image frame becomes available to the SurfaceTexture. |
void
|
updateTexImage()
Update the texture image to the most recent frame from the image stream. |
Protected methods | |
|---|---|
void
|
finalize()
Called by the garbage collector on an object when garbage collection determines that there are no more references to the object. |
Inherited methods | |
|---|---|
Public constructors
SurfaceTexture
public SurfaceTexture (int texName)
Construct a new SurfaceTexture to stream images to a given OpenGL texture.
| Parameters | |
|---|---|
texName |
int: the OpenGL texture object name (e.g. generated via glGenTextures) |
| Throws | |
|---|---|
Surface.OutOfResourcesException |
If the SurfaceTexture cannot be created. |
SurfaceTexture
public SurfaceTexture (int texName,
boolean singleBufferMode)
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.
| Parameters | |
|---|---|
texName |
int: the OpenGL texture object name (e.g. generated via glGenTextures) |
singleBufferMode |
boolean: whether the SurfaceTexture will be in single buffered mode. |
| Throws | |
|---|---|
Surface.OutOfResourcesException |
If the SurfaceTexture cannot be created. |
SurfaceTexture
public SurfaceTexture (boolean singleBufferMode)
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.
Unlike SurfaceTexture(int, boolean), which takes an OpenGL texture object name,
this constructor creates the SurfaceTexture in detached mode. A texture name must be passed
in using attachToGLContext(int) before calling releaseTexImage() and producing
image content using OpenGL ES.
| Parameters | |
|---|---|
singleBufferMode |
boolean: whether the SurfaceTexture will be in single buffered mode. |
| Throws | |
|---|---|
Surface.OutOfResourcesException |
If the SurfaceTexture cannot be created. |
Public methods
attachToGLContext
public void attachToGLContext (int texName)
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.
| Parameters | |
|---|---|
texName |
int: The name of the OpenGL ES texture that will be created. This texture name
must be unused in the OpenGL ES context that is current on the calling thread. |
detachFromGLContext
public void detachFromGLContext ()
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.
getDataSpace
public int getDataSpace ()
Retrieve the dataspace associated with the texture image.
getTimestamp
public long getTimestamp ()
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. 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.
For camera sources, timestamps should be strictly monotonic. Timestamps from MediaPlayer
sources may be reset when the playback position is set. For EGL and Vulkan producers, the
timestamp is the desired present time set with the EGL_ANDROID_presentation_time or
VK_GOOGLE_display_timing extensions.
| Returns | |
|---|---|
long |
|
getTransformMatrix
public void getTransformMatrix (float[] mtx)
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.
If the underlying buffer has a crop associated with it, the transformation will also include a slight scale to cut off a 1-texel border around the edge of the crop. This ensures that when the texture is bilinear sampled that no texels outside of the buffer's valid region are accessed by the GPU, avoiding any sampling artifacts when scaling.
| Parameters | |
|---|---|
mtx |
float: the array into which the 4x4 matrix will be stored. The array must have exactly
16 elements. |
isReleased
public boolean isReleased ()
Returns true if the SurfaceTexture was released.
| Returns | |
|---|---|
boolean |
|
See also:
release
public void release ()
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 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.
See also:
releaseTexImage
public void releaseTexImage ()
Releases 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).
setDefaultBufferSize
public void setDefaultBufferSize (int width,
int height)
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
Surface.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 Surface.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.
| Parameters | |
|---|---|
width |
int |
height |
int |
setOnFrameAvailableListener
public void setOnFrameAvailableListener (SurfaceTexture.OnFrameAvailableListener listener, Handler handler)
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.
| Parameters | |
|---|---|
listener |
SurfaceTexture.OnFrameAvailableListener: The listener to use, or null to remove the listener. |
handler |
Handler: The handler on which the listener should be invoked, or null
to use an arbitrary thread. |
setOnFrameAvailableListener
public void setOnFrameAvailableListener (SurfaceTexture.OnFrameAvailableListener listener)
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.
| Parameters | |
|---|---|
listener |
SurfaceTexture.OnFrameAvailableListener: The listener to use, or null to remove the listener. |
updateTexImage
public void updateTexImage ()
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.
Protected methods
finalize
protected void finalize ()
Called by the garbage collector on an object when garbage collection
determines that there are no more references to the object.
A subclass overrides the finalize method to dispose of
system resources or to perform other cleanup.
The general contract of finalize is that it is invoked
if and when the Java virtual
machine has determined that there is no longer any
means by which this object can be accessed by any thread that has
not yet died, except as a result of an action taken by the
finalization of some other object or class which is ready to be
finalized. The finalize method may take any action, including
making this object available again to other threads; the usual purpose
of finalize, however, is to perform cleanup actions before
the object is irrevocably discarded. For example, the finalize method
for an object that represents an input/output connection might perform
explicit I/O transactions to break the connection before the object is
permanently discarded.
The finalize method of class Object performs no
special action; it simply returns normally. Subclasses of
Object may override this definition.
The Java programming language does not guarantee which thread will
invoke the finalize method for any given object. It is
guaranteed, however, that the thread that invokes finalize will not
be holding any user-visible synchronization locks when finalize is
invoked. If an uncaught exception is thrown by the finalize method,
the exception is ignored and finalization of that object terminates.
After the finalize method has been invoked for an object, no
further action is taken until the Java virtual machine has again
determined that there is no longer any means by which this object can
be accessed by any thread that has not yet died, including possible
actions by other objects or classes which are ready to be finalized,
at which point the object may be discarded.
The finalize method is never invoked more than once by a Java
virtual machine for any given object.
Any exception thrown by the finalize method causes
the finalization of this object to be halted, but is otherwise
ignored.
| Throws | |
|---|---|
Throwable |
|
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Last updated 2024-06-18 UTC.