android/media/Image.java

/*
 * Copyright (C) 2013 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package android.media;

import java.nio.ByteBuffer;
import java.lang.AutoCloseable;

/**
 * <p>A single complete image buffer to use with a media source such as a
 * {@link MediaCodec} or a
 * {@link android.hardware.camera2.CameraDevice CameraDevice}.</p>
 *
 * <p>This class allows for efficient direct application access to the pixel
 * data of the Image through one or more
 * {@link java.nio.ByteBuffer ByteBuffers}. Each buffer is encapsulated in a
 * {@link Plane} that describes the layout of the pixel data in that plane. Due
 * to this direct access, and unlike the {@link android.graphics.Bitmap Bitmap} class,
 * Images are not directly usable as as UI resources.</p>
 *
 * <p>Since Images are often directly produced or consumed by hardware
 * components, they are a limited resource shared across the system, and should
 * be closed as soon as they are no longer needed.</p>
 *
 * <p>For example, when using the {@link ImageReader} class to read out Images
 * from various media sources, not closing old Image objects will prevent the
 * availability of new Images once
 * {@link ImageReader#getMaxImages the maximum outstanding image count} is
 * reached. When this happens, the function acquiring new Images will typically
 * throw an {@link IllegalStateException}.</p>
 *
 * @see ImageReader
 */
public abstract class Image implements AutoCloseable {
    /**
     * @hide
     */
    protected Image() {
    }

    /**
     * Get the format for this image. This format determines the number of
     * ByteBuffers needed to represent the image, and the general layout of the
     * pixel data in each in ByteBuffer.
     *
     * <p>
     * The format is one of the values from
     * {@link android.graphics.ImageFormat ImageFormat}. The mapping between the
     * formats and the planes is as follows:
     * </p>
     *
     * <table>
     * <tr>
     *   <th>Format</th>
     *   <th>Plane count</th>
     *   <th>Layout details</th>
     * </tr>
     * <tr>
     *   <td>{@link android.graphics.ImageFormat#JPEG JPEG}</td>
     *   <td>1</td>
     *   <td>Compressed data, so row and pixel strides are 0. To uncompress, use
     *      {@link android.graphics.BitmapFactory#decodeByteArray BitmapFactory#decodeByteArray}.
     *   </td>
     * </tr>
     * <tr>
     *   <td>{@link android.graphics.ImageFormat#YUV_420_888 YUV_420_888}</td>
     *   <td>3</td>
     *   <td>A luminance plane followed by the Cb and Cr chroma planes.
     *     The chroma planes have half the width and height of the luminance
     *     plane (4:2:0 subsampling). Each pixel sample in each plane has 8 bits.
     *     Each plane has its own row stride and pixel stride.</td>
     * </tr>
     * <tr>
     *   <td>{@link android.graphics.ImageFormat#RAW_SENSOR RAW_SENSOR}</td>
     *   <td>1</td>
     *   <td>A single plane of raw sensor image data, with 16 bits per color
     *     sample. The details of the layout need to be queried from the source of
     *     the raw sensor data, such as
     *     {@link android.hardware.camera2.CameraDevice CameraDevice}.
     *   </td>
     * </tr>
     * </table>
     *
     * @see android.graphics.ImageFormat
     */
    public abstract int getFormat();

    /**
     * The width of the image in pixels. For formats where some color channels
     * are subsampled, this is the width of the largest-resolution plane.
     */
    public abstract int getWidth();

    /**
     * The height of the image in pixels. For formats where some color channels
     * are subsampled, this is the height of the largest-resolution plane.
     */
    public abstract int getHeight();

    /**
     * Get the timestamp associated with this frame.
     * <p>
     * The timestamp is measured in nanoseconds, and is monotonically
     * increasing. However, the zero point and whether the timestamp can be
     * compared against other sources of time or images depend on the source of
     * this image.
     * </p>
     */
    public abstract long getTimestamp();

    /**
     * Get the array of pixel planes for this Image. The number of planes is
     * determined by the format of the Image.
     */
    public abstract Plane[] getPlanes();

    /**
     * Free up this frame for reuse.
     * <p>
     * After calling this method, calling any methods on this {@code Image} will
     * result in an {@link IllegalStateException}, and attempting to read from
     * {@link ByteBuffer ByteBuffers} returned by an earlier
     * {@link Plane#getBuffer} call will have undefined behavior.
     * </p>
     */
    @Override
    public abstract void close();

    /**
     * <p>A single color plane of image data.</p>
     *
     * <p>The number and meaning of the planes in an Image are determined by the
     * format of the Image.</p>
     *
     * <p>Once the Image has been closed, any access to the the plane's
     * ByteBuffer will fail.</p>
     *
     * @see #getFormat
     */
    public static abstract class Plane {
        /**
         * @hide
         */
        protected Plane() {
        }

        /**
         * <p>The row stride for this color plane, in bytes.</p>
         *
         * <p>This is the distance between the start of two consecutive rows of
         * pixels in the image. The row stride is always greater than 0.</p>
         */
        public abstract int getRowStride();
        /**
         * <p>The distance between adjacent pixel samples, in bytes.</p>
         *
         * <p>This is the distance between two consecutive pixel values in a row
         * of pixels. It may be larger than the size of a single pixel to
         * account for interleaved image data or padded formats.
         * The pixel stride is always greater than 0.</p>
         */
        public abstract int getPixelStride();
        /**
         * <p>Get a direct {@link java.nio.ByteBuffer ByteBuffer}
         * containing the frame data.</p>
         *
         * <p>In particular, the buffer returned will always have
         * {@link java.nio.ByteBuffer#isDirect isDirect} return {@code true}, so
         * the underlying data could be mapped as a pointer in JNI without doing
         * any copies with {@code GetDirectBufferAddress}.</p>
         *
         * @return the byte buffer containing the image data for this plane.
         */
        public abstract ByteBuffer getBuffer();
    }

}