// This example is from the book _Java AWT Reference_ by John Zukowski.
// Written by John Zukowski. Copyright (c) 1997 O'Reilly & Associates.
// You may study, use, modify, and distribute this example for any purpose.
// This example is provided WITHOUT WARRANTY either expressed or implied.
import java.awt.*;
import java.awt.image.*;
import java.util.*;
import java.io.*;
public class PPMImageDecoder implements ImageProducer {
/* Since done in-memory, only one consumer */
private ImageConsumer consumer;
boolean loadError = false;
int width;
int height;
int store[][];
Hashtable props = new Hashtable();
/* Format of Ppm file is single pass/frame, w/ complete scan lines in order */
private static int PpmHints = (ImageConsumer.TOPDOWNLEFTRIGHT |
ImageConsumer.COMPLETESCANLINES |
ImageConsumer.SINGLEPASS |
ImageConsumer.SINGLEFRAME);
/* There is only a single consumer. When it registers, produce image. */
/* On error, notify consumer */
public synchronized void addConsumer (ImageConsumer ic) {
consumer = ic;
try {
produce();
} catch (Exception e) {
if (consumer != null)
consumer.imageComplete (ImageConsumer.IMAGEERROR);
}
consumer = null;
}
/* If consumer passed to routine is single consumer, return true, else false */
public synchronized boolean isConsumer (ImageConsumer ic) {
return (ic == consumer);
}
/* Disables consumer if currently consuming */
public synchronized void removeConsumer (ImageConsumer ic) {
if (consumer == ic)
consumer = null;
}
/* Production is done by adding conumer */
public void startProduction (ImageConsumer ic) {
addConsumer (ic);
}
public void requestTopDownLeftRightResend (ImageConsumer ic) {
// Not needed. The data is always in this format.
}
/* Production Process:
Prerequisite: Image already read into store array. (readImage)
props / width / height already set (readImage)
Assumes RGB Color Model - would need to filter to change.
Sends Ppm Image data to consumer.
Pixels sent one row at a time.
*/
private void produce () {
ColorModel cm = ColorModel.getRGBdefault();
if (consumer != null) {
if (loadError) {
consumer.imageComplete (ImageConsumer.IMAGEERROR);
} else {
consumer.setDimensions (width, height);
consumer.setProperties (props);
consumer.setColorModel (cm);
consumer.setHints (PpmHints);
for (int j=0;j<height;j++)
consumer.setPixels (0, j, width, 1, cm, store[j], 0, width);
consumer.imageComplete (ImageConsumer.STATICIMAGEDONE);
}
}
}
/* Allows reading to be from internal byte array, in addition to disk/socket */
public void readImage (byte b[]) {
readImage (new ByteArrayInputStream (b));
}
/* readImage reads image data from Stream */
/* parses data for PPM format */
/* closes inputstream when done */
public void readImage (InputStream is) {
long tm = System.currentTimeMillis();
boolean raw=false;
DataInputStream dis = null;
BufferedInputStream bis = null;
try {
bis = new BufferedInputStream (is);
dis = new DataInputStream (bis);
String word;
word = readWord (dis);
if ("P6".equals (word)) {
raw = true;
} else if ("P3".equals (word)) {
raw = false;
} else {
throw (new AWTException ("Invalid Format " + word));
}
width = Integer.parseInt (readWord (dis));
height = Integer.parseInt (readWord (dis));
// Could put comments in props - makes readWord more complex
int maxColors = Integer.parseInt (readWord (dis));
if ((maxColors < 0) || (maxColors > 255)) {
throw (new AWTException ("Invalid Colors " + maxColors));
}
store = new int[height][width];
if (raw) {
byte row[] = new byte [width*3];
for (int i=0;i<height;i++){
dis.readFully (row);
for (int j=0,k=0;j<width;j++,k+=3) {
int red = row[k];
int green = row[k+1];
int blue = row[k+2];
if (red < 0)
red +=256;
if (green < 0)
green +=256;
if (blue < 0)
blue +=256;
store[i][j] = (0xff<< 24) | (red << 16) | (green << 8) | blue;
}
}
} else {
for (int i=0;i<height;i++) {
for (int j=0;j<width;j++) {
int red = Integer.parseInt (readWord (dis));
int green = Integer.parseInt (readWord (dis));
int blue = Integer.parseInt (readWord (dis));
store[i][j] = (0xff<< 24) | (red << 16) | (green << 8) | blue;
}
}
}
} catch (IOException io) {
loadError = true;
System.out.println ("IO Exception " + io.getMessage());
} catch (AWTException awt) {
loadError = true;
System.out.println ("AWT Exception " + awt.getMessage());
} catch (NoSuchElementException nse) {
loadError = true;
System.out.println ("No Such Element Exception " + nse.getMessage());
} finally {
try {
if (dis != null)
dis.close();
if (bis != null)
bis.close();
if (is != null)
is.close();
} catch (IOException io) {
System.out.println ("IO Exception " + io.getMessage());
}
}
System.out.println ("Done in " + (System.currentTimeMillis() - tm) + " ms");
}
/* readWord returns a word of text from stream */
/* Ignores PPM comment lines. */
/* word defined to be something wrapped by whitespace */
private String readWord (InputStream is) throws IOException {
StringBuffer buf = new StringBuffer();
int b;
do { // get rid of leading whitespace
if ((b=is.read()) == -1)
throw new EOFException();
if ((char)b == '#') { // read to end of line - ppm comment
DataInputStream dis = new DataInputStream (is);
dis.readLine();
b = ' '; // ensure more reading
}
} while (Character.isSpace ((char)b));
do {
buf.append ((char)(b));
if ((b=is.read()) == -1)
throw new EOFException();
} while (!Character.isSpace ((char)b)); // reads first space
return buf.toString();
}
}
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