/*
* Copyright 2023 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 androidx.media3.extractor.png;
import static androidx.media3.common.util.Assertions.checkNotNull;
import static androidx.media3.extractor.ImageExtractorUtil.IMAGE_TRACK_ID;
import static java.lang.annotation.ElementType.TYPE_USE;
import androidx.annotation.IntDef;
import androidx.media3.common.C;
import androidx.media3.common.Format;
import androidx.media3.common.MimeTypes;
import androidx.media3.common.util.ParsableByteArray;
import androidx.media3.common.util.UnstableApi;
import androidx.media3.extractor.Extractor;
import androidx.media3.extractor.ExtractorInput;
import androidx.media3.extractor.ExtractorOutput;
import androidx.media3.extractor.PositionHolder;
import androidx.media3.extractor.SingleSampleSeekMap;
import androidx.media3.extractor.TrackOutput;
import java.io.IOException;
import java.lang.annotation.Documented;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;
import org.checkerframework.checker.nullness.qual.MonotonicNonNull;
/** Extracts data from the PNG container format. */
@UnstableApi
// TODO: b/289989902 - Move methods of this class into ImageExtractorUtil once there are multiple
// image extractors.
public final class PngExtractor implements Extractor {
/** Parser states. */
@Documented
@Retention(RetentionPolicy.SOURCE)
@Target(TYPE_USE)
@IntDef({STATE_READING_IMAGE, STATE_ENDED})
private @interface State {}
private static final int STATE_READING_IMAGE = 1;
private static final int STATE_ENDED = 2;
private static final int PNG_FILE_SIGNATURE_LENGTH = 2;
// See PNG (Portable Network Graphics) Specification, Version 1.2, Section 12.12 and Section 3.1.
private static final int PNG_FILE_SIGNATURE = 0x8950;
private static final int FIXED_READ_LENGTH = 1024;
private final ParsableByteArray scratch;
private @State int state;
private @MonotonicNonNull ExtractorOutput extractorOutput;
/** Creates an instance. */
public PngExtractor() {
scratch = new ParsableByteArray(PNG_FILE_SIGNATURE_LENGTH);
}
@Override
public boolean sniff(ExtractorInput input) throws IOException {
scratch.reset(/* limit= */ PNG_FILE_SIGNATURE_LENGTH);
input.peekFully(scratch.getData(), /* offset= */ 0, PNG_FILE_SIGNATURE_LENGTH);
return scratch.readUnsignedShort() == PNG_FILE_SIGNATURE;
}
@Override
public void init(ExtractorOutput output) {
extractorOutput = output;
outputImageTrackAndSeekMap();
}
@Override
public @ReadResult int read(ExtractorInput input, PositionHolder seekPosition)
throws IOException {
switch (state) {
case STATE_READING_IMAGE:
readSegment(input);
return RESULT_CONTINUE;
case STATE_ENDED:
return RESULT_END_OF_INPUT;
default:
throw new IllegalStateException();
}
}
private void readSegment(ExtractorInput input) throws IOException {
TrackOutput trackOutput =
checkNotNull(extractorOutput).track(IMAGE_TRACK_ID, C.TRACK_TYPE_IMAGE);
int result = trackOutput.sampleData(input, FIXED_READ_LENGTH, /* allowEndOfInput= */ true);
if (result == C.RESULT_END_OF_INPUT) {
state = STATE_ENDED;
}
}
private void outputImageTrackAndSeekMap() {
ExtractorOutput extractorOutput = checkNotNull(this.extractorOutput);
TrackOutput imageTrackOutput = extractorOutput.track(IMAGE_TRACK_ID, C.TRACK_TYPE_IMAGE);
imageTrackOutput.format(
new Format.Builder()
.setContainerMimeType(MimeTypes.IMAGE_PNG)
.setTileCountHorizontal(1)
.setTileCountVertical(1)
.build());
extractorOutput.endTracks();
extractorOutput.seekMap(new SingleSampleSeekMap(/* durationUs= */ C.TIME_UNSET));
state = STATE_READING_IMAGE;
}
@Override
public void seek(long position, long timeUs) {
if (position == 0) {
state = STATE_READING_IMAGE;
}
}
@Override
public void release() {
// Do nothing.
}
}