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PngImage.java
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PngImage.java
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/*
* PNG library (Java)
*
* Copyright (c) Project Nayuki
* MIT License. See readme file.
* https://www.nayuki.io/page/png-library
*/
package io.nayuki.png;
import java.io.BufferedInputStream;
import java.io.BufferedOutputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.HashSet;
import java.util.List;
import java.util.Objects;
import java.util.Optional;
import java.util.Set;
import io.nayuki.png.chunk.Chunk;
import io.nayuki.png.chunk.Idat;
import io.nayuki.png.chunk.Iend;
import io.nayuki.png.chunk.Ihdr;
import io.nayuki.png.chunk.Plte;
/**
* A structured representation of chunks that form a PNG file. Instances
* are mutable. There is some degree of validation and exclusion of invalid
* data. This class operates at the next level up from {@link XngFile}.
* <p>When serializing a {@code PngImage} object, the resulting
* list of chunks is composed in the following order:</p>
* <ol>
* <li>Field {@code ihdr} (must be present)</li>
* <li>Field {@code afterIhdr} (zero or more chunks)</li>
* <li>Field {@code idats} (one or more chunks)</li>
* <li>Field {@code afterIdats} (zero or more chunks)</li>
* <li>Constant {@code Iend.SINGLETON}</li>
* </ol>
*/
public final class PngImage {
/**
* Reads the specified input file and returns a new
* {@code PngImage} object representing chunks read.
* @param inFile the input file to read from
* @return a new {@code XngFile} object representing chunks read
* @throws NullPointerException if {@code inFile} is {@code null}
* @throws IllegalArgumentException if the file contains invalid data in the header
* signature, chunk outer structure, chunk inner structure, or constraints between chunks
* @throws IOException if an I/O exception occurs
*/
public static PngImage read(File inFile) throws IOException {
Objects.requireNonNull(inFile);
try (var in = new BufferedInputStream(new FileInputStream(inFile))) {
return read(in);
}
}
/**
* Reads the specified input stream and returns a new {@code PngImage}
* object representing chunks read. This does not close the stream.
* This reads until the end of stream if no exception is thrown.
* @param in the input stream to read from
* @return a new {@code XngFile} object representing chunks read
* @throws NullPointerException if {@code inFile} is {@code null}
* @throws IllegalArgumentException if the stream contains invalid data in the header
* signature, chunk outer structure, chunk inner structure, or constraints between chunks
* @throws IOException if an I/O exception occurs
*/
public static PngImage read(InputStream in) throws IOException {
Objects.requireNonNull(in);
XngFile xng = XngFile.read(in, true);
if (xng.type() != XngFile.Type.PNG)
throw new IllegalArgumentException("File signature is not PNG");
return new PngImage(xng.chunks());
}
/**
* From the specified lists, returns the single chunk that matches the specified type or empty.
* @param <T> the chunk type
* @param type the class object of the desired chunk type
* @param lists the list of lists of chunks to read from
* @return the single chunk matching the type or empty
* @throws IllegalArgumentException if multiple chunks match the type
*/
@SafeVarargs
public static <T> Optional<T> getChunk(Class<T> type, List<? extends Chunk>... lists) {
Optional<T> result = Optional.empty();
for (List<? extends Chunk> lst : lists) {
for (Chunk chk : lst) {
if (type.isInstance(chk)) {
if (result.isPresent())
throw new IllegalArgumentException("Multiple chunks with given type");
result = Optional.of(type.cast(chk));
}
}
}
return result;
}
/**
* From the specified lists, returns a readable list of all the
* chunks that match the specified type, possibly an empty list.
* @param <T> the chunk type
* @param type the class object of the desired chunk type
* @param lists the list of lists of chunks to read from
* @return a list (not {@code null}) of all the chunks matching the type
*/
@SafeVarargs
public static <T> List<T> getChunks(Class<T> type, List<? extends Chunk>... lists) {
List<T> result = new ArrayList<>();
for (List<? extends Chunk> lst : lists) {
for (Chunk chk : lst) {
if (type.isInstance(chk))
result.add(type.cast(chk));
}
}
return result;
}
/** The single IHDR chunk, if present. */
public Optional<Ihdr> ihdr = Optional.empty();
/** The chunks positioned after IHDR. */
public List<Chunk> afterIhdr = new ArrayList<>();
/** The consecutive IDAT chunks. */
public List<Idat> idats = new ArrayList<>();
/** The chunks positioned after the IDAT chunks. */
public List<Chunk> afterIdats = new ArrayList<>();
/**
* Constructs a blank PNG image where all fields are initially empty (not {@code null}).
*/
public PngImage() {}
private PngImage(List<Chunk> chunks) {
enum State {
BEFORE_IHDR,
AFTER_IHDR,
DURING_IDATS,
AFTER_IDATS,
AFTER_IEND,
}
State state = State.BEFORE_IHDR;
Set<String> seenChunkTypes = new HashSet<>();
for (Chunk chunk : chunks) {
String type = chunk.getType();
if (!seenChunkTypes.add(type) && UNIQUE_CHUNK_TYPES.contains(type))
throw new IllegalArgumentException("Duplicate " + type + " chunk");
state = switch (state) {
case BEFORE_IHDR -> {
if (chunk instanceof Ihdr chk) {
ihdr = Optional.of(chk);
yield State.AFTER_IHDR;
} else
throw new IllegalArgumentException("Expected IHDR chunk");
}
case AFTER_IHDR -> {
if (chunk instanceof Idat chk1) {
idats.add(chk1);
yield State.DURING_IDATS;
} else if (chunk instanceof Iend)
throw new IllegalArgumentException("Unexpected IEND chunk");
else {
afterIhdr.add(chunk);
yield State.AFTER_IHDR;
}
}
case DURING_IDATS -> {
if (chunk instanceof Plte)
throw new IllegalArgumentException("Unexpected PLTE chunk");
else if (chunk instanceof Idat chk) {
idats.add(chk);
yield State.DURING_IDATS;
} else if (chunk instanceof Iend)
yield State.AFTER_IEND;
else {
afterIdats.add(chunk);
yield State.AFTER_IDATS;
}
}
case AFTER_IDATS -> {
if (chunk instanceof Plte)
throw new IllegalArgumentException("Unexpected PLTE chunk");
else if (chunk instanceof Iend)
yield State.AFTER_IEND;
else if (chunk instanceof Idat)
throw new IllegalArgumentException("Non-consecutive IDAT chunk");
else {
afterIdats.add(chunk);
yield State.AFTER_IDATS;
}
}
case AFTER_IEND ->
throw new IllegalArgumentException("Unexpected chunk after IEND");
};
}
if (state != State.AFTER_IEND)
throw new IllegalArgumentException("Missing some required chunks");
if (PngImage.getChunk(Plte.class, afterIhdr).isPresent()) {
boolean seenPlte = false;
for (Chunk chk : afterIhdr) {
if (chk instanceof Plte)
seenPlte = true;
else if (!seenPlte && AFTER_PLTE_CHUNK_TYPES.contains(chk.getType()))
throw new IllegalArgumentException("Unexpected " + chk.getType() + " chunk before PLTE");
else if (seenPlte && BEFORE_PLTE_CHUNK_TYPES.contains(chk.getType()))
throw new IllegalArgumentException("Unexpected " + chk.getType() + " chunk after PLTE");
}
}
}
private static final Set<String> UNIQUE_CHUNK_TYPES = new HashSet<>(Arrays.asList(
"acTL",
"bKGD",
"cHRM",
"gAMA",
"hIST",
"iCCP",
"IEND",
"IHDR",
"pHYs",
"PLTE",
"sBIT",
"sRGB",
"tIME",
"tRNS"));
private static final Set<String> BEFORE_PLTE_CHUNK_TYPES = new HashSet<>(Arrays.asList(
"cHRM",
"gAMA",
"iCCP",
"sBIT",
"sRGB"));
private static final Set<String> AFTER_PLTE_CHUNK_TYPES = new HashSet<>(Arrays.asList(
"bKGD",
"hIST",
"tRNS"));
/**
* Writes the signature and chunks of this PNG file to the specified output file.
* @throws NullPointerException if {@code outFile}
* or any of this object's fields is {@code null}
* @throws IllegalStateException if the current
* lists of chunks do not form a valid PNG file
* @throws IOException if an I/O exception occurs
*/
public void write(File outFile) throws IOException {
Objects.requireNonNull(outFile);
try (var out = new BufferedOutputStream(new FileOutputStream(outFile))) {
write(out);
}
}
/**
* Writes the signature and chunks of this PNG file to the
* specified output stream. This does not close the stream.
* @throws NullPointerException if {@code out}
* or any of this object's fields is {@code null}
* @throws IllegalStateException if the current
* lists of chunks do not form a valid PNG file
* @throws IOException if an I/O exception occurs
*/
public void write(OutputStream out) throws IOException {
Objects.requireNonNull(out);
List<Chunk> chunks = new ArrayList<>();
chunks.add(ihdr.orElseThrow(() -> new IllegalStateException("Missing IHDR chunk")));
chunks.addAll(afterIhdr);
if (idats.isEmpty())
throw new IllegalStateException("Missing IDAT chunks");
chunks.addAll(idats);
chunks.addAll(afterIdats);
chunks.add(Iend.SINGLETON);
new XngFile(XngFile.Type.PNG, chunks).write(out);
}
}