SurfaceTexture.java revision e5e0c50f7dfaccc220725c5595080e921ffda1e4
1/* 2 * Copyright (C) 2010 The Android Open Source Project 3 * 4 * Licensed under the Apache License, Version 2.0 (the "License"); 5 * you may not use this file except in compliance with the License. 6 * You may obtain a copy of the License at 7 * 8 * http://www.apache.org/licenses/LICENSE-2.0 9 * 10 * Unless required by applicable law or agreed to in writing, software 11 * distributed under the License is distributed on an "AS IS" BASIS, 12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13 * See the License for the specific language governing permissions and 14 * limitations under the License. 15 */ 16 17package android.graphics; 18 19import java.lang.ref.WeakReference; 20import android.os.Handler; 21import android.os.Looper; 22import android.os.Message; 23 24/** 25 * Captures frames from an image stream as an OpenGL ES texture. 26 * 27 * <p>The image stream may come from either camera preview or video decode. A SurfaceTexture 28 * may be used in place of a SurfaceHolder when specifying the output destination of a 29 * {@link android.hardware.Camera} or {@link android.media.MediaPlayer} 30 * object. Doing so will cause all the frames from the image stream to be sent to the 31 * SurfaceTexture object rather than to the device's display. When {@link #updateTexImage} is 32 * called, the contents of the texture object specified when the SurfaceTexture was created are 33 * updated to contain the most recent image from the image stream. This may cause some frames of 34 * the stream to be skipped. 35 * 36 * <p>When sampling from the texture one should first transform the texture coordinates using the 37 * matrix queried via {@link #getTransformMatrix(float[])}. The transform matrix may change each 38 * time {@link #updateTexImage} is called, so it should be re-queried each time the texture image 39 * is updated. 40 * This matrix transforms traditional 2D OpenGL ES texture coordinate column vectors of the form (s, 41 * t, 0, 1) where s and t are on the inclusive interval [0, 1] to the proper sampling location in 42 * the streamed texture. This transform compensates for any properties of the image stream source 43 * that cause it to appear different from a traditional OpenGL ES texture. For example, sampling 44 * from the bottom left corner of the image can be accomplished by transforming the column vector 45 * (0, 0, 0, 1) using the queried matrix, while sampling from the top right corner of the image can 46 * be done by transforming (1, 1, 0, 1). 47 * 48 * <p>The texture object uses the GL_TEXTURE_EXTERNAL_OES texture target, which is defined by the 49 * <a href="http://www.khronos.org/registry/gles/extensions/OES/OES_EGL_image_external.txt"> 50 * GL_OES_EGL_image_external</a> OpenGL ES extension. This limits how the texture may be used. 51 * Each time the texture is bound it must be bound to the GL_TEXTURE_EXTERNAL_OES target rather than 52 * the GL_TEXTURE_2D target. Additionally, any OpenGL ES 2.0 shader that samples from the texture 53 * must declare its use of this extension using, for example, an "#extension 54 * GL_OES_EGL_image_external : require" directive. Such shaders must also access the texture using 55 * the samplerExternalOES GLSL sampler type. 56 * 57 * <p>SurfaceTexture objects may be created on any thread. {@link #updateTexImage} may only be 58 * called on the thread with the OpenGL ES context that contains the texture object. The 59 * frame-available callback is called on an arbitrary thread, so unless special care is taken {@link 60 * #updateTexImage} should not be called directly from the callback. 61 */ 62public class SurfaceTexture { 63 64 private EventHandler mEventHandler; 65 private OnFrameAvailableListener mOnFrameAvailableListener; 66 67 /** 68 * This field is used by native code, do not access or modify. 69 */ 70 private int mSurfaceTexture; 71 72 /** 73 * Callback interface for being notified that a new stream frame is available. 74 */ 75 public interface OnFrameAvailableListener { 76 void onFrameAvailable(SurfaceTexture surfaceTexture); 77 } 78 79 /** 80 * Exception thrown when a surface couldn't be created or resized 81 */ 82 public static class OutOfResourcesException extends Exception { 83 public OutOfResourcesException() { 84 } 85 public OutOfResourcesException(String name) { 86 super(name); 87 } 88 } 89 90 /** 91 * Construct a new SurfaceTexture to stream images to a given OpenGL texture. 92 * 93 * @param texName the OpenGL texture object name (e.g. generated via glGenTextures) 94 */ 95 public SurfaceTexture(int texName) { 96 Looper looper; 97 if ((looper = Looper.myLooper()) != null) { 98 mEventHandler = new EventHandler(looper); 99 } else if ((looper = Looper.getMainLooper()) != null) { 100 mEventHandler = new EventHandler(looper); 101 } else { 102 mEventHandler = null; 103 } 104 nativeInit(texName, new WeakReference<SurfaceTexture>(this)); 105 } 106 107 /** 108 * Register a callback to be invoked when a new image frame becomes available to the 109 * SurfaceTexture. Note that this callback may be called on an arbitrary thread, so it is not 110 * safe to call {@link #updateTexImage} without first binding the OpenGL ES context to the 111 * thread invoking the callback. 112 */ 113 public void setOnFrameAvailableListener(OnFrameAvailableListener l) { 114 mOnFrameAvailableListener = l; 115 } 116 117 /** 118 * Set the size of buffers returned by requestBuffers when a width and height 119 * of zero is requested. 120 * 121 * @hide Pending approval by API council. 122 */ 123 public void setDefaultBufferSize(int width, int height) { 124 nativeSetDefaultBufferSize(width, height); 125 } 126 127 /** 128 * Update the texture image to the most recent frame from the image stream. This may only be 129 * called while the OpenGL ES context that owns the texture is bound to the thread. It will 130 * implicitly bind its texture to the GL_TEXTURE_EXTERNAL_OES texture target. 131 */ 132 public void updateTexImage() { 133 nativeUpdateTexImage(); 134 } 135 136 /** 137 * Retrieve the 4x4 texture coordinate transform matrix associated with the texture image set by 138 * the most recent call to updateTexImage. 139 * 140 * This transform matrix maps 2D homogeneous texture coordinates of the form (s, t, 0, 1) with s 141 * and t in the inclusive range [0, 1] to the texture coordinate that should be used to sample 142 * that location from the texture. Sampling the texture outside of the range of this transform 143 * is undefined. 144 * 145 * The matrix is stored in column-major order so that it may be passed directly to OpenGL ES via 146 * the glLoadMatrixf or glUniformMatrix4fv functions. 147 * 148 * @param mtx the array into which the 4x4 matrix will be stored. The array must have exactly 149 * 16 elements. 150 */ 151 public void getTransformMatrix(float[] mtx) { 152 // Note we intentionally don't check mtx for null, so this will result in a 153 // NullPointerException. But it's safe because it happens before the call to native. 154 if (mtx.length != 16) { 155 throw new IllegalArgumentException(); 156 } 157 nativeGetTransformMatrix(mtx); 158 } 159 160 /** 161 * Retrieve the timestamp associated with the texture image set by the most recent call to 162 * updateTexImage. 163 * 164 * This timestamp is in nanoseconds, and is guaranteed to be monotonically increasing. The 165 * specific meaning and zero point of the timestamp depends on the source providing images to 166 * the SurfaceTexture. Unless otherwise specified by the image source, timestamps cannot 167 * generally be compared across SurfaceTexture instances, or across multiple program 168 * invocations. It is mostly useful for determining time offsets between subsequent frames. 169 */ 170 public long getTimestamp() { 171 return nativeGetTimestamp(); 172 } 173 174 protected void finalize() throws Throwable { 175 try { 176 nativeFinalize(); 177 } finally { 178 super.finalize(); 179 } 180 } 181 182 private class EventHandler extends Handler { 183 public EventHandler(Looper looper) { 184 super(looper); 185 } 186 187 @Override 188 public void handleMessage(Message msg) { 189 if (mOnFrameAvailableListener != null) { 190 mOnFrameAvailableListener.onFrameAvailable(SurfaceTexture.this); 191 } 192 } 193 } 194 195 /** 196 * This method is invoked from native code only. 197 */ 198 @SuppressWarnings({"UnusedDeclaration"}) 199 private static void postEventFromNative(Object selfRef) { 200 WeakReference weakSelf = (WeakReference)selfRef; 201 SurfaceTexture st = (SurfaceTexture)weakSelf.get(); 202 if (st == null) { 203 return; 204 } 205 206 if (st.mEventHandler != null) { 207 Message m = st.mEventHandler.obtainMessage(); 208 st.mEventHandler.sendMessage(m); 209 } 210 } 211 212 private native void nativeInit(int texName, Object weakSelf); 213 private native void nativeFinalize(); 214 private native void nativeGetTransformMatrix(float[] mtx); 215 private native long nativeGetTimestamp(); 216 private native void nativeSetDefaultBufferSize(int width, int height); 217 private native void nativeUpdateTexImage(); 218 219 /* 220 * We use a class initializer to allow the native code to cache some 221 * field offsets. 222 */ 223 private static native void nativeClassInit(); 224 static { nativeClassInit(); } 225} 226