CameraNDK: fill in more NDK API documents
This change adds document for ACaptureRequest, ACameraMetadata,
AImage and AImageReader.
Bug: 27102995
Change-Id: I79d88f73258c01ebeabcd5b4e3b90996759cb021
diff --git a/include/ndk/NdkImageReader.h b/include/ndk/NdkImageReader.h
index 9e7483d..7c7ec6a 100644
--- a/include/ndk/NdkImageReader.h
+++ b/include/ndk/NdkImageReader.h
@@ -44,38 +44,253 @@
extern "C" {
#endif
+/**
+ * AImage is an opaque type that allows direct application access to image data rendered into a
+ * {@link ANativeWindow}.
+ */
typedef struct AImageReader AImageReader;
+/**
+ * Create a new reader for images of the desired size and format.
+ *
+ * <p>
+ * The maxImages parameter determines the maximum number of {@link AImage} objects that can be
+ * acquired from the {@link AImageReader} simultaneously. Requesting more buffers will use up
+ * more memory, so it is important to use only the minimum number necessary for the use case.
+ * </p>
+ * <p>
+ * The valid sizes and formats depend on the source of the image data.
+ * </p>
+ *
+ * @param width The default width in pixels of the Images that this reader will produce.
+ * @param height The default height in pixels of the Images that this reader will produce.
+ * @param format The format of the Image that this reader will produce. This must be one of the
+ * AIMAGE_FORMAT_* enum value defined in {@link AIMAGE_FORMATS}. Note that not all
+ * formats are supported, like {@link AIMAGE_FORMAT_PRIVATE}.
+ * @param maxImages The maximum number of images the user will want to access simultaneously. This
+ * should be as small as possible to limit memory use. Once maxImages Images are obtained
+ * by the user, one of them has to be released before a new {@link AImage} will become
+ * available for access through {@link AImageReader_acquireLatestImage} or
+ * {@link AImageReader_acquireNextImage}. Must be greater than 0.
+ * @param reader The created image reader will be filled here if the method call succeeeds.
+ *
+ * @return <ul>
+ * <li>{@link AMEDIA_OK} if the method call succeeds.</li>
+ * <li>{@link AMEDIA_ERROR_INVALID_PARAMETER} if reader is NULL, or one or more of width,
+ * height, format, maxImages arguments is not supported.</li>
+ * <li>{@link AMEDIA_ERROR_UNKNOWN} if the method fails for some other reasons.</li></ul>
+ *
+ * @see AImage
+ */
media_status_t AImageReader_new(
int32_t width, int32_t height, int32_t format, int32_t maxImages,
/*out*/AImageReader** reader);
-// Return all images acquired from this AImageReader back to system and delete
-// the AImageReader instance from memory
-// Do NOT use `reader` after this call
+/**
+ * Delete an {@link AImageReader} and return all images generated by this reader to system.
+ *
+ * <p>This method will return all {@link AImage} objects acquired by this reader (via
+ * {@link AImageReader_acquireNextImage} or {@link AImageReader_acquireLatestImage}) to system,
+ * making any of data pointers obtained from {@link AImage_getPlaneData} invalid. Do NOT access
+ * the reader object or any of those data pointers after this method returns.</p>
+ *
+ * @param reader The image reader to be deleted.
+ */
void AImageReader_delete(AImageReader* reader);
-// Do NOT call ANativeWindow_release on the output. Just use AImageReader_delete.
-media_status_t AImageReader_getWindow(AImageReader*, /*out*/ANativeWindow** window);
+/**
+ * Get a {@link ANativeWindow} that can be used to produce {@link AImage} for this image reader.
+ *
+ * @param reader The image reader of interest.
+ * @param window The output {@link ANativeWindow} will be filled here if the method call succeeds.
+ * The {@link ANativeWindow} is managed by this image reader. Do NOT call
+ * {@link ANativeWindow_release} on it. Instead, use {@link AImageReader_delete}.
+ *
+ * @return <ul>
+ * <li>{@link AMEDIA_OK} if the method call succeeds.</li>
+ * <li>{@link AMEDIA_ERROR_INVALID_PARAMETER} if reader or window is NULL.</li></ul>
+ */
+media_status_t AImageReader_getWindow(AImageReader* reader, /*out*/ANativeWindow** window);
+/**
+ * Query the default width of the {@link AImage} generated by this reader, in pixels.
+ *
+ * <p>The width may be overridden by the producer sending buffers to this reader's
+ * {@link ANativeWindow}. If so, the actual width of the images can be found using
+ * {@link AImage_getWidth}.</p>
+ *
+ * @param reader The image reader of interest.
+ * @param width the default width of the reader will be filled here if the method call succeeeds.
+ *
+ * @return <ul>
+ * <li>{@link AMEDIA_OK} if the method call succeeds.</li>
+ * <li>{@link AMEDIA_ERROR_INVALID_PARAMETER} if reader or width is NULL.</li></ul>
+ */
media_status_t AImageReader_getWidth(const AImageReader* reader, /*out*/int32_t* width);
+
+/**
+ * Query the default height of the {@link AImage} generated by this reader, in pixels.
+ *
+ * <p>The height may be overridden by the producer sending buffers to this reader's
+ * {@link ANativeWindow}. If so, the actual height of the images can be found using
+ * {@link AImage_getHeight}.</p>
+ *
+ * @param reader The image reader of interest.
+ * @param height the default height of the reader will be filled here if the method call succeeeds.
+ *
+ * @return <ul>
+ * <li>{@link AMEDIA_OK} if the method call succeeds.</li>
+ * <li>{@link AMEDIA_ERROR_INVALID_PARAMETER} if reader or height is NULL.</li></ul>
+ */
media_status_t AImageReader_getHeight(const AImageReader* reader, /*out*/int32_t* height);
+
+/**
+ * Query the format of the {@link AImage} generated by this reader.
+ *
+ * @param reader The image reader of interest.
+ * @param format the fromat of the reader will be filled here if the method call succeeeds. The
+ * value will be one of the AIMAGE_FORMAT_* enum value defiend in {@link NdkImage.h}.
+ *
+ * @return <ul>
+ * <li>{@link AMEDIA_OK} if the method call succeeds.</li>
+ * <li>{@link AMEDIA_ERROR_INVALID_PARAMETER} if reader or format is NULL.</li></ul>
+ */
media_status_t AImageReader_getFormat(const AImageReader* reader, /*out*/int32_t* format);
+
+/**
+ * Query the maximum number of concurrently acquired {@link AImage}s of this reader.
+ *
+ * @param reader The image reader of interest.
+ * @param maxImages the maximum number of concurrently acquired images of the reader will be filled
+ * here if the method call succeeeds.
+ *
+ * @return <ul>
+ * <li>{@link AMEDIA_OK} if the method call succeeds.</li>
+ * <li>{@link AMEDIA_ERROR_INVALID_PARAMETER} if reader or maxImages is NULL.</li></ul>
+ */
media_status_t AImageReader_getMaxImages(const AImageReader* reader, /*out*/int32_t* maxImages);
+/**
+ * Acquire the next {@link AImage} from the image reader's queue.
+ *
+ * <p>Warning: Consider using {@link AImageReader_acquireLatestImage} instead, as it will
+ * automatically release older images, and allow slower-running processing routines to catch
+ * up to the newest frame. Usage of {@link AImageReader_acquireNextImage} is recommended for
+ * batch/background processing. Incorrectly using this method can cause images to appear
+ * with an ever-increasing delay, followed by a complete stall where no new images seem to appear.
+ * </p>
+ *
+ * <p>
+ * This method will fail if {@link AImageReader_getMaxImages maxImages} have been acquired with
+ * {@link AImageReader_acquireNextImage} or {@link AImageReader_acquireLatestImage}. In particular
+ * a sequence of {@link AImageReader_acquireNextImage} or {@link AImageReader_acquireLatestImage}
+ * calls greater than {@link AImageReader_getMaxImages maxImages} without calling
+ * {@link AImage_delete} in-between will exhaust the underlying queue. At such a time,
+ * {@link AMEDIA_IMGREADER_MAX_IMAGES_ACQUIRED} will be returned until more images are released with
+ * {@link AImage_delete}.
+ * </p>
+ *
+ * @param reader The image reader of interest.
+ * @param image the acquired {@link AImage} will be filled here if the method call succeeeds.
+ *
+ * @return <ul>
+ * <li>{@link AMEDIA_OK} if the method call succeeds.</li>
+ * <li>{@link AMEDIA_ERROR_INVALID_PARAMETER} if reader or image is NULL.</li>
+ * <li>{@link AMEDIA_IMGREADER_MAX_IMAGES_ACQUIRED} if the number of concurrently acquired
+ * images has reached the limit.</li>
+ * <li>{@link AMEDIA_IMGREADER_NO_BUFFER_AVAILABLE} if there is no buffers currently
+ * available in the reader queue.</li>
+ * <li>{@link AMEDIA_ERROR_UNKNOWN} if the method fails for some other reasons.</li></ul>
+ *
+ * @see AImageReader_acquireLatestImage
+ */
media_status_t AImageReader_acquireNextImage(AImageReader* reader, /*out*/AImage** image);
+/**
+
+ * Acquire the latest {@link AImage} from the image reader's queue, dropping older images.
+ *
+ * <p>
+ * This operation will acquire all the images possible from the image reader, but
+ * {@link AImage_delete} all images that aren't the latest. This function is recommended to use over
+ * {@link AImageReader_acquireNextImage} for most use-cases, as it's more suited for real-time
+ * processing.
+ * </p>
+ * <p>
+ * Note that {@link AImageReader_getMaxImages maxImages} should be at least 2 for
+ * {@link AImageReader_acquireLatestImage} to be any different than
+ * {@link AImageReader_acquireNextImage} - discarding all-but-the-newest {@link AImage} requires
+ * temporarily acquiring two {@link AImage}s at once. Or more generally, calling
+ * {@link AImageReader_acquireLatestImage} with less than two images of margin, that is
+ * (maxImages - currentAcquiredImages < 2) will not discard as expected.
+ * </p>
+ * <p>
+ * This method will fail if {@link AImageReader_getMaxImages maxImages} have been acquired with
+ * {@link AImageReader_acquireNextImage} or {@link AImageReader_acquireLatestImage}. In particular
+ * a sequence of {@link AImageReader_acquireNextImage} or {@link AImageReader_acquireLatestImage}
+ * calls greater than {@link AImageReader_getMaxImages maxImages} without calling
+ * {@link AImage_delete} in-between will exhaust the underlying queue. At such a time,
+ * {@link AMEDIA_IMGREADER_MAX_IMAGES_ACQUIRED} will be returned until more images are released with
+ * {@link AImage_delete}.
+ * </p>
+ *
+ * @param reader The image reader of interest.
+ * @param image the acquired {@link AImage} will be filled here if the method call succeeeds.
+ *
+ * @return <ul>
+ * <li>{@link AMEDIA_OK} if the method call succeeds.</li>
+ * <li>{@link AMEDIA_ERROR_INVALID_PARAMETER} if reader or image is NULL.</li>
+ * <li>{@link AMEDIA_IMGREADER_MAX_IMAGES_ACQUIRED} if the number of concurrently acquired
+ * images has reached the limit.</li>
+ * <li>{@link AMEDIA_IMGREADER_NO_BUFFER_AVAILABLE} if there is no buffers currently
+ * available in the reader queue.</li>
+ * <li>{@link AMEDIA_ERROR_UNKNOWN} if the method fails for some other reasons.</li></ul>
+ *
+ * @see AImageReader_acquireNextImage
+ */
media_status_t AImageReader_acquireLatestImage(AImageReader* reader, /*out*/AImage** image);
-// The callback happens on one dedicated thread per AImageReader instance
-// It's okay to use AImageReader_*/AImage_* APIs within the callback
+
+/**
+ * The definition of {@link AImageReader} new image available callback.
+ *
+ * @param context The optional application context provided by user in
+ * {@link AImageReader_setImageListener}.
+ * @param session The camera capture session whose state is changing.
+ */
typedef void (*AImageReader_ImageCallback)(void* context, AImageReader* reader);
typedef struct AImageReader_ImageListener {
- void* context; // optional application context.
+ /// optional application context.
+ void* context;
+
+ /**
+ * This callback is called when there is a new image available for in the image reader's queue.
+ *
+ * <p>The callback happens on one dedicated thread per {@link AImageReader} instance. It is okay
+ * to use AImageReader_* and AImage_* methods within the callback. Note that it is possible that
+ * calling {@link AImageReader_acquireNextImage} or {@link AImageReader_acquireLatestImage}
+ * returns {@link AMEDIA_IMGREADER_NO_BUFFER_AVAILABLE} within this callback. For example, when
+ * there are multiple images and callbacks queued, if application called
+ * {@link AImageReader_acquireLatestImage}, some images will be returned to system before their
+ * corresponding callback is executed.</p>
+ */
AImageReader_ImageCallback onImageAvailable;
} AImageReader_ImageListener;
+/**
+ * Set the onImageAvailable listener of this image reader.
+ *
+ * <p>Note that calling this method will replace previously registered listeners.</p>
+ *
+ * @param reader The image reader of interest.
+ * @param listener the {@link AImageReader_ImageListener} to be registered. Set this to NULL if
+ * application no longer needs to listen to new images.
+ *
+ * @return <ul>
+ * <li>{@link AMEDIA_OK} if the method call succeeds.</li>
+ * <li>{@link AMEDIA_ERROR_INVALID_PARAMETER} if reader is NULL.</li></ul>
+ */
media_status_t AImageReader_setImageListener(
AImageReader* reader, AImageReader_ImageListener* listener);