com.drew.metadata.gif.GifReader Maven / Gradle / Ivy
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This is a fork of com.drewnoakes' metadata-extractor that relocates com.adobe.internal to com.adobe.
Java library for extracting EXIF, IPTC, XMP, ICC and other metadata from image and video files.
/*
* Copyright 2002-2019 Drew Noakes and contributors
*
* 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.
*
* More information about this project is available at:
*
* https://drewnoakes.com/code/exif/
* https://github.com/drewnoakes/metadata-extractor
*/
package com.drew.metadata.gif;
import com.drew.lang.ByteArrayReader;
import com.drew.lang.Charsets;
import com.drew.lang.SequentialReader;
import com.drew.lang.annotations.NotNull;
import com.drew.lang.annotations.Nullable;
import com.drew.metadata.*;
import com.drew.metadata.gif.GifControlDirectory.DisposalMethod;
import com.drew.metadata.icc.IccReader;
import com.drew.metadata.xmp.XmpReader;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
/**
* Reader of GIF encoded data.
*
* Resources:
*
* - https://wiki.whatwg.org/wiki/GIF
* - https://www.w3.org/Graphics/GIF/spec-gif89a.txt
* - http://web.archive.org/web/20100929230301/http://www.etsimo.uniovi.es/gifanim/gif87a.txt
*
*
* @author Drew Noakes https://drewnoakes.com
* @author Kevin Mott https://github.com/kwhopper
*/
public class GifReader
{
private static final String GIF_87A_VERSION_IDENTIFIER = "87a";
private static final String GIF_89A_VERSION_IDENTIFIER = "89a";
public void extract(@NotNull final SequentialReader reader, final @NotNull Metadata metadata)
{
reader.setMotorolaByteOrder(false);
GifHeaderDirectory header;
try {
header = readGifHeader(reader);
metadata.addDirectory(header);
} catch (IOException ex) {
metadata.addDirectory(new ErrorDirectory("IOException processing GIF data"));
return;
}
if(header.hasErrors())
return;
try {
// Skip over any global colour table if GlobalColorTable is present.
Integer globalColorTableSize = null;
try {
boolean hasGlobalColorTable = header.getBoolean(GifHeaderDirectory.TAG_HAS_GLOBAL_COLOR_TABLE);
if(hasGlobalColorTable) {
globalColorTableSize = header.getInteger(GifHeaderDirectory.TAG_COLOR_TABLE_SIZE);
}
} catch (MetadataException e) {
// This exception should never occur here.
metadata.addDirectory(new ErrorDirectory("GIF did not had hasGlobalColorTable bit."));
}
if (globalColorTableSize != null)
{
// Colour table has R/G/B byte triplets
reader.skip(3 * globalColorTableSize);
}
// After the header comes a sequence of blocks
while (true)
{
byte marker;
try {
marker = reader.getInt8();
} catch (IOException ex) {
return;
}
switch (marker)
{
case (byte)'!': // 0x21
{
readGifExtensionBlock(reader, metadata);
break;
}
case (byte)',': // 0x2c
{
metadata.addDirectory(readImageBlock(reader));
// skip image data blocks
skipBlocks(reader);
break;
}
case (byte)';': // 0x3b
{
// terminator
return;
}
default:
{
// Anything other than these types is unexpected.
// GIF87a spec says to keep reading until a separator is found.
// GIF89a spec says file is corrupt.
metadata.addDirectory(new ErrorDirectory("Unknown gif block marker found."));
return;
}
}
}
} catch (IOException e) {
metadata.addDirectory(new ErrorDirectory("IOException processing GIF data"));
}
}
private static GifHeaderDirectory readGifHeader(@NotNull final SequentialReader reader) throws IOException
{
// FILE HEADER
//
// 3 - signature: "GIF"
// 3 - version: either "87a" or "89a"
//
// LOGICAL SCREEN DESCRIPTOR
//
// 2 - pixel width
// 2 - pixel height
// 1 - screen and color map information flags (0 is LSB)
// 0-2 Size of the global color table
// 3 Color table sort flag (89a only)
// 4-6 Color resolution
// 7 Global color table flag
// 1 - background color index
// 1 - pixel aspect ratio
GifHeaderDirectory headerDirectory = new GifHeaderDirectory();
String signature = reader.getString(3);
if (!signature.equals("GIF"))
{
headerDirectory.addError("Invalid GIF file signature");
return headerDirectory;
}
String version = reader.getString(3);
if (!version.equals(GIF_87A_VERSION_IDENTIFIER) && !version.equals(GIF_89A_VERSION_IDENTIFIER)) {
headerDirectory.addError("Unexpected GIF version");
return headerDirectory;
}
headerDirectory.setString(GifHeaderDirectory.TAG_GIF_FORMAT_VERSION, version);
// LOGICAL SCREEN DESCRIPTOR
headerDirectory.setInt(GifHeaderDirectory.TAG_IMAGE_WIDTH, reader.getUInt16());
headerDirectory.setInt(GifHeaderDirectory.TAG_IMAGE_HEIGHT, reader.getUInt16());
short flags = reader.getUInt8();
// First three bits = (BPP - 1)
int colorTableSize = 1 << ((flags & 7) + 1);
int bitsPerPixel = ((flags & 0x70) >> 4) + 1;
boolean hasGlobalColorTable = (flags >> 7) != 0;
headerDirectory.setInt(GifHeaderDirectory.TAG_COLOR_TABLE_SIZE, colorTableSize);
if (version.equals(GIF_89A_VERSION_IDENTIFIER)) {
boolean isColorTableSorted = (flags & 8) != 0;
headerDirectory.setBoolean(GifHeaderDirectory.TAG_IS_COLOR_TABLE_SORTED, isColorTableSorted);
}
headerDirectory.setInt(GifHeaderDirectory.TAG_BITS_PER_PIXEL, bitsPerPixel);
headerDirectory.setBoolean(GifHeaderDirectory.TAG_HAS_GLOBAL_COLOR_TABLE, hasGlobalColorTable);
headerDirectory.setInt(GifHeaderDirectory.TAG_BACKGROUND_COLOR_INDEX, reader.getUInt8());
int aspectRatioByte = reader.getUInt8();
if (aspectRatioByte != 0) {
float pixelAspectRatio = (float)((aspectRatioByte + 15d) / 64d);
headerDirectory.setFloat(GifHeaderDirectory.TAG_PIXEL_ASPECT_RATIO, pixelAspectRatio);
}
return headerDirectory;
}
private static void readGifExtensionBlock(SequentialReader reader, Metadata metadata) throws IOException
{
byte extensionLabel = reader.getInt8();
short blockSizeBytes = reader.getUInt8();
long blockStartPos = reader.getPosition();
switch (extensionLabel)
{
case (byte) 0x01:
Directory plainTextBlock = readPlainTextBlock(reader, blockSizeBytes);
if (plainTextBlock != null)
metadata.addDirectory(plainTextBlock);
break;
case (byte) 0xf9:
metadata.addDirectory(readControlBlock(reader));
break;
case (byte) 0xfe:
metadata.addDirectory(readCommentBlock(reader, blockSizeBytes));
break;
case (byte) 0xff:
readApplicationExtensionBlock(reader, blockSizeBytes, metadata);
break;
default:
metadata.addDirectory(new ErrorDirectory(String.format("Unsupported GIF extension block with type 0x%02X.", extensionLabel)));
break;
}
long skipCount = blockStartPos + blockSizeBytes - reader.getPosition();
if (skipCount > 0)
reader.skip(skipCount);
}
@Nullable
private static Directory readPlainTextBlock(SequentialReader reader, int blockSizeBytes) throws IOException
{
// It seems this extension is deprecated. If somebody finds an image with this in it, could implement here.
// Just skip the entire block for now.
if (blockSizeBytes != 12)
return new ErrorDirectory(String.format("Invalid GIF plain text block size. Expected 12, got %d.", blockSizeBytes));
// skip 'blockSizeBytes' bytes
reader.skip(12);
// keep reading and skipping until a 0 byte is reached
skipBlocks(reader);
return null;
}
private static GifCommentDirectory readCommentBlock(SequentialReader reader, int blockSizeBytes) throws IOException
{
byte[] buffer = gatherBytes(reader, blockSizeBytes);
return new GifCommentDirectory(new StringValue(buffer, Charsets.ASCII));
}
private static void readApplicationExtensionBlock(SequentialReader reader, int blockSizeBytes, Metadata metadata) throws IOException
{
if (blockSizeBytes != 11)
{
metadata.addDirectory(new ErrorDirectory(String.format("Invalid GIF application extension block size. Expected 11, got %d.", blockSizeBytes)));
return;
}
String extensionType = reader.getString(blockSizeBytes, Charsets.UTF_8);
if (extensionType.equals("XMP DataXMP"))
{
// XMP data extension
byte[] xmpBytes = gatherBytes(reader);
int xmpLengh = xmpBytes.length - 257; // Exclude the "magic trailer", see XMP Specification Part 3, 1.1.2 GIF
if (xmpLengh > 0) {
// Only extract valid blocks
new XmpReader().extract(xmpBytes, 0, xmpBytes.length - 257, metadata, null);
}
}
else if (extensionType.equals("ICCRGBG1012"))
{
// ICC profile extension
byte[] iccBytes = gatherBytes(reader, ((int) reader.getByte()) & 0xff);
if (iccBytes.length != 0)
new IccReader().extract(new ByteArrayReader(iccBytes), metadata);
}
else if (extensionType.equals("NETSCAPE2.0"))
{
reader.skip(2);
// Netscape's animated GIF extension
// Iteration count (0 means infinite)
int iterationCount = reader.getUInt16();
// Skip terminator
reader.skip(1);
GifAnimationDirectory animationDirectory = new GifAnimationDirectory();
animationDirectory.setInt(GifAnimationDirectory.TAG_ITERATION_COUNT, iterationCount);
metadata.addDirectory(animationDirectory);
}
else
{
skipBlocks(reader);
}
}
private static GifControlDirectory readControlBlock(SequentialReader reader) throws IOException
{
GifControlDirectory directory = new GifControlDirectory();
short packedFields = reader.getUInt8();
directory.setObject(GifControlDirectory.TAG_DISPOSAL_METHOD, DisposalMethod.typeOf((packedFields >> 2) & 7));
directory.setBoolean(GifControlDirectory.TAG_USER_INPUT_FLAG, (packedFields & 2) >> 1 == 1);
directory.setBoolean(GifControlDirectory.TAG_TRANSPARENT_COLOR_FLAG, (packedFields & 1) == 1);
directory.setInt(GifControlDirectory.TAG_DELAY, reader.getUInt16());
directory.setInt(GifControlDirectory.TAG_TRANSPARENT_COLOR_INDEX, reader.getUInt8());
// skip 0x0 block terminator
reader.skip(1);
return directory;
}
private static GifImageDirectory readImageBlock(SequentialReader reader) throws IOException
{
GifImageDirectory imageDirectory = new GifImageDirectory();
imageDirectory.setInt(GifImageDirectory.TAG_LEFT, reader.getUInt16());
imageDirectory.setInt(GifImageDirectory.TAG_TOP, reader.getUInt16());
imageDirectory.setInt(GifImageDirectory.TAG_WIDTH, reader.getUInt16());
imageDirectory.setInt(GifImageDirectory.TAG_HEIGHT, reader.getUInt16());
byte flags = reader.getByte();
boolean hasColorTable = (flags >> 7) != 0;
boolean isInterlaced = (flags & 0x40) != 0;
imageDirectory.setBoolean(GifImageDirectory.TAG_HAS_LOCAL_COLOUR_TABLE, hasColorTable);
imageDirectory.setBoolean(GifImageDirectory.TAG_IS_INTERLACED, isInterlaced);
if (hasColorTable)
{
boolean isColorTableSorted = (flags & 0x20) != 0;
imageDirectory.setBoolean(GifImageDirectory.TAG_IS_COLOR_TABLE_SORTED, isColorTableSorted);
int bitsPerPixel = (flags & 0x7) + 1;
imageDirectory.setInt(GifImageDirectory.TAG_LOCAL_COLOUR_TABLE_BITS_PER_PIXEL, bitsPerPixel);
// skip color table
reader.skip(3 * (2 << (flags & 0x7)));
}
// skip "LZW Minimum Code Size" byte
reader.getByte();
return imageDirectory;
}
private static byte[] gatherBytes(SequentialReader reader) throws IOException
{
ByteArrayOutputStream bytes = new ByteArrayOutputStream();
byte[] buffer = new byte[257];
while (true)
{
byte b = reader.getByte();
if (b == 0)
return bytes.toByteArray();
int bInt = b & 0xFF;
buffer[0] = b;
reader.getBytes(buffer, 1, bInt);
bytes.write(buffer, 0, bInt + 1);
}
}
private static byte[] gatherBytes(SequentialReader reader, int firstLength) throws IOException
{
ByteArrayOutputStream buffer = new ByteArrayOutputStream();
int length = firstLength;
while (length > 0)
{
buffer.write(reader.getBytes(length), 0, length);
length = reader.getByte() & 0xff;
}
return buffer.toByteArray();
}
private static void skipBlocks(SequentialReader reader) throws IOException
{
while (true)
{
short length = reader.getUInt8();
if (length == 0)
return;
reader.skip(length);
}
}
}