WebPChunkVp8.java
/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You 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 org.apache.commons.imaging.formats.webp.chunks;
import java.io.IOException;
import java.io.PrintWriter;
import org.apache.commons.imaging.ImagingException;
/**
* VP8 (bitstream) chunk.
*
* <pre>{@code
* 0 1 2 3
* 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
* | ChunkHeader('VP8 ') |
* | |
* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
* : VP8 data :
* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
* }</pre>
*
* @see <a href="https://developers.google.com/speed/webp/docs/riff_container#simple_file_format_lossy">Simple File Format (Lossy)</a>
* @see <a href="https://datatracker.ietf.org/doc/html/rfc6386">VP8 Data Format and Decoding Guide</a>
* @since 1.0-alpha4
*/
public final class WebPChunkVp8 extends WebPChunk {
private final int versionNumber;
private final int width;
private final int height;
private final int horizontalScale;
private final int verticalScale;
/**
* Create a VP8 chunk.
*
* @param type chunk type.
* @param size chunk size.
* @param bytes chunk data.
* @throws ImagingException if the chunk data and the size provided do not match.
*/
public WebPChunkVp8(final int type, final int size, final byte[] bytes) throws ImagingException {
super(type, size, bytes);
if (size < 10) {
throw new ImagingException("Invalid VP8 chunk");
}
/*
* https://datatracker.ietf.org/doc/html/rfc6386#section-9
*/
/*
* Frame Header:
*
* 1. A 1-bit frame type (0 for key frames, 1 for interframes).
*
* 2. A 3-bit version number (0 - 3 are defined as four different profiles with different decoding complexity; other values may be defined for future
* variants of the VP8 data format).
*
* 3. A 1-bit show_frame flag (0 when current frame is not for display, 1 when current frame is for display).
*
* 4. A 19-bit field containing the size of the first data partition in bytes.
*/
final int b0 = bytes[0] & 0xFF;
// int b1 = bytes[1] & 0xFF;
// int b2 = bytes[2] & 0xFF;
if ((b0 & 0b1) != 0) {
throw new ImagingException("Invalid VP8 chunk: should be key frame");
}
this.versionNumber = (b0 & 0b1110) >> 1;
if ((b0 & 0b0001_0000) == 0) {
throw new ImagingException("Invalid VP8 chunk: frame should to be display");
}
// int firstDataPartitionSize = (b0 >>> 5) + (b1 << 3) + (b2 << 11);
/*
* Key Frame:
*
* Start code byte 0 0x9d Start code byte 1 0x01 Start code byte 2 0x2a
*
* 16 bits : (2 bits Horizontal Scale << 14) | Width (14 bits) 16 bits : (2 bits Vertical Scale << 14) | Height (14 bits)
*/
final int b3 = bytes[3] & 0xFF;
final int b4 = bytes[4] & 0xFF;
final int b5 = bytes[5] & 0xFF;
final int b6 = bytes[6] & 0xFF;
final int b7 = bytes[7] & 0xFF;
final int b8 = bytes[8] & 0xFF;
final int b9 = bytes[9] & 0xFF;
if (b3 != 0x9D || b4 != 0x01 || b5 != 0x2A) {
throw new ImagingException("Invalid VP8 chunk: invalid signature");
}
this.width = b6 + ((b7 & 0b0011_1111) << 8);
this.horizontalScale = b7 >> 6;
this.height = b8 + ((b9 & 0b0011_1111) << 8);
this.verticalScale = b9 >> 6;
}
@Override
public void dump(final PrintWriter pw, final int offset) throws ImagingException, IOException {
super.dump(pw, offset);
pw.println(" Version Number: " + getVersionNumber());
pw.println(" Width: " + getWidth());
pw.println(" Height: " + getHeight());
pw.println(" Horizontal Scale: " + getHorizontalScale());
pw.println(" Vertical Scale: " + getVerticalScale());
}
/**
* @return the height.
*/
public int getHeight() {
return height;
}
/**
* @return the horizontal scale.
*/
public int getHorizontalScale() {
return horizontalScale;
}
/**
* @return the version number.
*/
public int getVersionNumber() {
return versionNumber;
}
/**
* @return the vertical scale.
*/
public int getVerticalScale() {
return verticalScale;
}
/**
* @return the width.
*/
public int getWidth() {
return width;
}
}