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* EPS comments are retrieved from EPS directory. Photoshop, ICC Profile, and XMP processing
* is passed to their respective reader.
*
* EPS Constraints (Source: https://www-cdf.fnal.gov/offline/PostScript/5001.PDF pg.18):
*
*
Max line length is 255 characters
*
Lines end with a CR(0xD) or LF(0xA) character (or both, in practice)
*
':' separates keywords (considered part of the keyword)
*
Whitespace is either a space(0x20) or tab(0x9)
*
If there is more than one header, the 1st is truth
*
*
* @author Payton Garland
*/
public class EpsReader
{
private int _previousTag;
/**
* Filter method that determines if file will contain an EPS Header. If it does, it will read the necessary
* data and then set the position to the beginning of the PostScript data. If it does not, the position will not
* be changed. After both scenarios, the main extract method is called.
*
* @param inputStream InputStream containing file
* @param metadata Metadata to add directory to and extracted data
*/
public void extract(@NotNull final InputStream inputStream, @NotNull final Metadata metadata) throws IOException
{
RandomAccessStreamReader reader = new RandomAccessStreamReader(inputStream);
EpsDirectory directory = new EpsDirectory();
metadata.addDirectory(directory);
/*
* 0xC5D0D3C6 signifies an EPS Header block which contains 32-bytes of basic information
*
* 0x25215053 (%!PS) signifies an EPS File and leads straight into the PostScript
*/
switch (reader.getInt32(0)) {
case 0xC5D0D3C6:
reader.setMotorolaByteOrder(false);
int postScriptOffset = reader.getInt32(4);
int postScriptLength = reader.getInt32(8);
int wmfOffset = reader.getInt32(12);
int wmfSize = reader.getInt32(16);
int tifOffset = reader.getInt32(20);
int tifSize = reader.getInt32(24);
//int checkSum = reader.getInt32(28);
// Get Tiff/WMF preview data if applicable
if (tifSize != 0) {
directory.setInt(EpsDirectory.TAG_TIFF_PREVIEW_SIZE, tifSize);
directory.setInt(EpsDirectory.TAG_TIFF_PREVIEW_OFFSET, tifOffset);
// Get Tiff metadata
try {
ByteArrayReader byteArrayReader = new ByteArrayReader(reader.getBytes(tifOffset, tifSize));
new TiffReader().processTiff(byteArrayReader, new PhotoshopTiffHandler(metadata, null), 0);
} catch (TiffProcessingException ex) {
directory.addError("Unable to process TIFF data: " + ex.getMessage());
}
} else if (wmfSize != 0) {
directory.setInt(EpsDirectory.TAG_WMF_PREVIEW_SIZE, wmfSize);
directory.setInt(EpsDirectory.TAG_WMF_PREVIEW_OFFSET, wmfOffset);
}
// TODO avoid allocating byte array here -- read directly from InputStream
extract(directory, metadata, new SequentialByteArrayReader(reader.getBytes(postScriptOffset, postScriptLength)));
break;
case 0x25215053:
inputStream.reset();
extract(directory, metadata, new StreamReader(inputStream));
break;
default:
directory.addError("File type not supported.");
break;
}
}
/**
* Main method that parses all comments and then distributes data extraction among other methods that parse the
* rest of file and store encountered data in metadata (if there exists an entry in EpsDirectory
* for the found data). Reads until a begin data/binary comment is found or _reader's estimated
* available data has run out (or AI09 End Private Data). Will extract data from normal EPS comments, Photoshop, ICC, and XMP.
*
* @param metadata Metadata to add directory to and extracted data
*/
private void extract(@NotNull final EpsDirectory directory, @NotNull Metadata metadata, @NotNull SequentialReader reader) throws IOException
{
StringBuilder line = new StringBuilder();
while (true) {
line.setLength(0);
// Read the next line, excluding any trailing newline character
// Note that for Windows-style line endings ("\r\n") the outer loop will be run a second time with an empty
// string, which is fine.
while (true) {
char c = (char)reader.getByte();
if (c == '\r' || c == '\n')
break;
line.append(c);
}
// Stop when we hit a line that is not a comment
if (line.length() != 0 && line.charAt(0) != '%')
break;
String name;
// ':' signifies there is an associated keyword (should be put in directory)
// otherwise, the name could be a marker
int colonIndex = line.indexOf(":");
if (colonIndex != -1) {
name = line.substring(0, colonIndex).trim();
String value = line.substring(colonIndex + 1).trim();
addToDirectory(directory, name, value);
} else {
name = line.toString().trim();
}
// Some comments will both have a value and signify a new block to follow
if (name.equals("%BeginPhotoshop")) {
extractPhotoshopData(metadata, reader);
} else if (name.equals("%%BeginICCProfile")) {
extractIccData(metadata, reader);
} else if (name.equals("%begin_xml_packet")) {
extractXmpData(metadata, reader);
}
}
}
/**
* Default case that adds comment with keyword to directory
*
* @param directory EpsDirectory to add extracted data to
* @param name String that holds name of current comment
* @param value String that holds value of current comment
*/
private void addToDirectory(@NotNull final EpsDirectory directory, String name, String value) throws IOException
{
Integer tag = EpsDirectory._tagIntegerMap.get(name);
if (tag == null)
return;
switch (tag) {
case EpsDirectory.TAG_IMAGE_DATA:
extractImageData(directory, value);
break;
case EpsDirectory.TAG_CONTINUE_LINE:
directory.setString(_previousTag, directory.getString(_previousTag) + " " + value);
break;
default:
if (EpsDirectory._tagNameMap.containsKey(tag) && !directory.containsTag(tag)) {
directory.setString(tag, value);
_previousTag = tag;
} else {
// Set previous tag to an Integer that doesn't exist in EpsDirectory
_previousTag = 0;
}
break;
}
_previousTag = tag;
}
/**
* Parses %ImageData comment which holds several values including width in px,
* height in px and color type.
*/
private static void extractImageData(@NotNull final EpsDirectory directory, String imageData) throws IOException
{
// %ImageData: 1000 1000 8 3 1 1000 7 "beginimage"
directory.setString(EpsDirectory.TAG_IMAGE_DATA, imageData.trim());
String[] imageDataParts = imageData.split(" ");
int width = Integer.parseInt(imageDataParts[0]);
int height = Integer.parseInt(imageDataParts[1]);
int colorType = Integer.parseInt(imageDataParts[3]);
// Only add values that are not already present
if (!directory.containsTag(EpsDirectory.TAG_IMAGE_WIDTH))
directory.setInt(EpsDirectory.TAG_IMAGE_WIDTH, width);
if (!directory.containsTag(EpsDirectory.TAG_IMAGE_HEIGHT))
directory.setInt(EpsDirectory.TAG_IMAGE_HEIGHT, height);
if (!directory.containsTag(EpsDirectory.TAG_COLOR_TYPE))
directory.setInt(EpsDirectory.TAG_COLOR_TYPE, colorType);
if (!directory.containsTag(EpsDirectory.TAG_RAM_SIZE)) {
int bytesPerPixel = 0;
if (colorType == 1)
bytesPerPixel = 1; // grayscale
else if (colorType == 2 || colorType == 3)
bytesPerPixel = 3; // Lab or RGB
else if (colorType == 4)
bytesPerPixel = 3; // CMYK
if (bytesPerPixel != 0)
directory.setInt(EpsDirectory.TAG_RAM_SIZE, bytesPerPixel * width * height);
}
}
/**
* Decodes a commented hex section, and uses {@link PhotoshopReader} to decode the resulting data.
*/
private static void extractPhotoshopData(@NotNull final Metadata metadata, @NotNull SequentialReader reader) throws IOException
{
byte[] buffer = decodeHexCommentBlock(reader);
if (buffer != null)
new PhotoshopReader().extract(new SequentialByteArrayReader(buffer), buffer.length, metadata);
}
/**
* Decodes a commented hex section, and uses {@link IccReader} to decode the resulting data.
*/
private static void extractIccData(@NotNull final Metadata metadata, @NotNull SequentialReader reader) throws IOException
{
byte[] buffer = decodeHexCommentBlock(reader);
if (buffer != null)
new IccReader().extract(new ByteArrayReader(buffer), metadata);
}
/**
* Extracts an XMP xpacket, and uses {@link XmpReader} to decode the resulting data.
*/
private static void extractXmpData(@NotNull final Metadata metadata, @NotNull SequentialReader reader) throws IOException
{
byte[] bytes = readUntil(reader, "".getBytes());
String xmp = new String(bytes, Charsets.UTF_8);
new XmpReader().extract(xmp, metadata);
}
/**
* Reads all bytes until the given sentinel is observed.
* The sentinel will be included in the returned bytes.
*/
private static byte[] readUntil(@NotNull SequentialReader reader, @NotNull byte[] sentinel) throws IOException
{
ByteArrayOutputStream bytes = new ByteArrayOutputStream();
final int length = sentinel.length;
int depth = 0;
while (depth != length) {
byte b = reader.getByte();
if (b == sentinel[depth])
depth++;
else
depth = 0;
bytes.write(b);
}
return bytes.toByteArray();
}
/**
* EPS files can contain hexadecimal-encoded ASCII blocks, each prefixed with "% ".
* This method reads such a block and returns a byte[] of the decoded contents.
* Reading stops at the first invalid line, which is discarded (it's a terminator anyway).
*
* For example:
*
* When calling this method, the reader must be positioned at the start of the first line containing
* hex data, not at the introductory line.
*
* @return The decoded bytes, or null if decoding failed.
*/
@Nullable
private static byte[] decodeHexCommentBlock(@NotNull SequentialReader reader) throws IOException
{
ByteArrayOutputStream bytes = new ByteArrayOutputStream();
// Use a state machine to efficiently parse data in a single traversal
final int AwaitingPercent = 0;
final int AwaitingSpace = 1;
final int AwaitingHex1 = 2;
final int AwaitingHex2 = 3;
int state = AwaitingPercent;
int carry = 0;
boolean done = false;
byte b = 0;
while (!done) {
b = reader.getByte();
switch (state) {
case AwaitingPercent: {
switch (b) {
case '\r':
case '\n':
case ' ':
// skip newline chars and spaces
break;
case '%':
state = AwaitingSpace;
break;
default:
return null;
}
break;
}
case AwaitingSpace: {
switch (b) {
case ' ':
state = AwaitingHex1;
break;
default:
done = true;
break;
}
break;
}
case AwaitingHex1: {
int i = tryHexToInt(b);
if (i != -1) {
carry = i * 16;
state = AwaitingHex2;
} else if (b == '\r' || b == '\n') {
state = AwaitingPercent;
} else {
return null;
}
break;
}
case AwaitingHex2: {
int i = tryHexToInt(b);
if (i == -1)
return null;
bytes.write(carry + i);
state = AwaitingHex1;
break;
}
}
}
// skip through the remainder of the last line
while (b != '\n')
b = reader.getByte();
return bytes.toByteArray();
}
/**
* Treats a byte as an ASCII character, and returns it's numerical value in hexadecimal.
* If conversion is not possible, returns -1.
*/
private static int tryHexToInt(byte b)
{
if (b >= '0' && b <= '9')
return b - '0';
if (b >= 'A' && b <= 'F')
return b - 'A' + 10;
if (b >= 'a' && b <= 'f')
return b - 'a' + 10;
return -1;
}
}
