SurfaceTexture
open class SurfaceTexture
| kotlin.Any | |
| ↳ | 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 android.view.Surface created from a SurfaceTexture can be used as an output destination for the android.hardware.camera2, android.media.MediaCodec, android.media.MediaPlayer, and android.renderscript.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 android.hardware.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 | |
|---|---|
| abstract |
Callback interface for being notified that a new stream frame is available. |
| open |
Exception thrown when a SurfaceTexture couldn't be created or resized. |
| Public constructors | |
|---|---|
SurfaceTexture(singleBufferMode: Boolean)Construct a new SurfaceTexture to stream images to a given OpenGL texture. |
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SurfaceTexture(texName: Int)Construct a new SurfaceTexture to stream images to a given OpenGL texture. |
|
SurfaceTexture(texName: Int, singleBufferMode: Boolean)Construct a new SurfaceTexture to stream images to a given OpenGL texture. |
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| Public methods | |
|---|---|
| open Unit |
attachToGLContext(texName: Int)Attach the SurfaceTexture to the OpenGL ES context that is current on the calling thread. |
| open Unit |
Detach the SurfaceTexture from the OpenGL ES context that owns the OpenGL ES texture object. |
| open Int |
Retrieve the dataspace associated with the texture image set by the most recent call to |
| open Long |
Retrieve the timestamp associated with the texture image set by the most recent call to |
| open Unit |
getTransformMatrix(mtx: FloatArray!)Retrieve the 4x4 texture coordinate transform matrix associated with the texture image set by the most recent call to |
| open Boolean |
Returns |
| open Unit |
release()
|
| open Unit |
Releases the texture content. |
| open Unit |
setDefaultBufferSize(width: Int, height: Int)Set the default size of the image buffers. |
| open Unit |
Register a callback to be invoked when a new image frame becomes available to the SurfaceTexture. |
| open Unit |
setOnFrameAvailableListener(listener: SurfaceTexture.OnFrameAvailableListener?, handler: Handler?)Register a callback to be invoked when a new image frame becomes available to the SurfaceTexture. |
| open Unit |
Update the texture image to the most recent frame from the image stream. |
| Protected methods | |
|---|---|
| open Unit |
finalize() |
Public constructors
SurfaceTexture
SurfaceTexture(singleBufferMode: Boolean)
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 before calling releaseTexImage() and producing image content using OpenGL ES.
| Parameters | |
|---|---|
singleBufferMode |
Boolean: whether the SurfaceTexture will be in single buffered mode. |
| Exceptions | |
|---|---|
android.view.Surface.OutOfResourcesException |
If the SurfaceTexture cannot be created. |
SurfaceTexture
SurfaceTexture(texName: Int)
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) |
| Exceptions | |
|---|---|
android.view.Surface.OutOfResourcesException |
If the SurfaceTexture cannot be created. |
SurfaceTexture
SurfaceTexture(
texName: Int,
singleBufferMode: Boolean)
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. |
| Exceptions | |
|---|---|
android.view.Surface.OutOfResourcesException |
If the SurfaceTexture cannot be created. |
Public methods
attachToGLContext
open fun attachToGLContext(texName: Int): Unit
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
open fun detachFromGLContext(): Unit
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 java.lang.IllegalStateException until a successful call to attachToGLContext 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
open fun getDataSpace(): Int
Retrieve the dataspace associated with the texture image set by the most recent call to updateTexImage.
getTimestamp
open fun getTimestamp(): Long
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.
getTransformMatrix
open fun getTransformMatrix(mtx: FloatArray!): Unit
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 |
FloatArray!: the array into which the 4x4 matrix will be stored. The array must have exactly 16 elements. |
isReleased
open fun isReleased(): Boolean
Returns true if the SurfaceTexture was released.
See Also
release
open fun release(): Unit
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
open fun releaseTexImage(): Unit
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
open fun setDefaultBufferSize(
width: Int,
height: Int
): Unit
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 android.graphics.Canvas (via android.view.Surface#lockCanvas), 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 android.graphics.Canvas this will be the next time android.view.Surface#lockCanvas 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 javax.microedition.khronos.opengles.GL10#glGetIntegerv). An error due to invalid dimensions might not be reported until updateTexImage() is called.
setOnFrameAvailableListener
open fun setOnFrameAvailableListener(listener: SurfaceTexture.OnFrameAvailableListener?): Unit
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. |
setOnFrameAvailableListener
open fun setOnFrameAvailableListener(
listener: SurfaceTexture.OnFrameAvailableListener?,
handler: Handler?
): Unit
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. |
updateTexImage
open fun updateTexImage(): Unit
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 open fun finalize(): Unit
| Exceptions | |
|---|---|
java.lang.Throwable |
the Exception raised by this method |