PGM_Reader.java

package ij.plugin;
import java.awt.*;
import java.awt.image.*;
import java.io.*;
import ij.*;
import ij.io.*;
import ij.process.*;

public class PGM_Reader extends ImagePlus implements PlugIn {

    private int width, height;
    private boolean rawBits;
    private boolean sixteenBits;
    
    public void run(String path) {
        
        IJ.showStatus("Opening: " + path);
        File fp = new File(path);
        ImageProcessor ip;
        try {
            ip = openFile(path);
        }
        catch (IOException e) {
            String msg = e.getMessage();
            IJ.showMessage("PGM Reader", msg.equals("")?""+e:msg);
            return;
        }

        setProcessor(fp.getName(), ip);
        if (path.equals(""))
            show();
    }

    public ImageProcessor openFile(String path) throws IOException {

        // updated this to no longer used deprecated StringTokenizer constructor
        // rumored not to work
        FileInputStream is = new FileInputStream(path);
        Reader r = new BufferedReader(new InputStreamReader(is));
        StreamTokenizer tok = new StreamTokenizer(r);

        // used to be
        //InputStream is = new BufferedInputStream();
        //StreamTokenizer tok = new StreamTokenizer(is); //deprecated, but it works

        tok.resetSyntax();
        tok.wordChars(33, 255);
        tok.whitespaceChars(0, ' ');
        tok.parseNumbers();
        tok.eolIsSignificant(true);
        tok.commentChar('#');
        openHeader(tok);
        if (sixteenBits)
            if(rawBits)
                return open16bitRawImage(is, width, height);
            else
                return open16bitAsciiImage(tok, width, height);
        else {
            byte[] pixels = new byte[width*height];
            ImageProcessor ip = new ByteProcessor(width, height, pixels, null);
            if (rawBits)
                openRawImage(is, width*height, pixels);
            else
                openAsciiImage(tok, width*height, pixels);
            return ip;
        }
    }

    public void openHeader(StreamTokenizer tok) throws IOException {
        String magicNumber = getWord(tok);
        if (magicNumber.equals("P5"))
            rawBits = true;
        else if (!magicNumber.equals("P2"))
            throw new IOException("PGM files must start with \"P2\" or \"P5\"");
        width = getInt(tok);
        height = getInt(tok);
        int maxValue = getInt(tok);
        if (width==-1 || height==-1 || maxValue==-1)
            throw new IOException("Error opening PGM header..");
        if(maxValue > 255)
            sixteenBits = true;
        else
            sixteenBits = false;
        String msg = "The maximum gray value is larger than ";
        if (sixteenBits && maxValue>65535)
            throw new IOException(msg + "65535.");
    }

    public void openAsciiImage(StreamTokenizer tok, int size, byte[] pixels) throws IOException {
        int i = 0;
        int inc = size/20;
        while (tok.nextToken() != tok.TT_EOF) {
            if (tok.ttype==tok.TT_NUMBER) {
                pixels[i++] = (byte)(((int)tok.nval)&255);
                if (i%inc==0)
                    IJ.showProgress(0.5+((double)i/size)/2.0);
            }
        }
        IJ.showProgress(1.0);
    }

    public void openRawImage(InputStream is, int size, byte[] pixels) throws IOException {
        int count = 0;
        while (count<size && count>=0)
            count = is.read(pixels, count, size-count);
    }

    public ImageProcessor open16bitRawImage(InputStream is, int width, int height) throws IOException {
        int size = width*height*2;
        byte[] bytes = new byte[size];
        int count = 0;
        while (count<size && count>=0)
            count = is.read(bytes, count, size-count);
        short[] pixels = new short[size/2];
        for (int i=0,j=0; i<size/2; i++,j+=2)
            pixels[i] = (short)(((bytes[j]&0xff)<<8) | (bytes[j+1]&0xff)); //big endian
        return new ShortProcessor(width, height, pixels, null);
    }
    
    public ImageProcessor open16bitAsciiImage(StreamTokenizer tok,
    int width, int height) throws IOException {
        int i = 0;
        int size = width * height;
        int inc = size/20; // Progress update interval
        short[] pixels = new short[size];
        while (tok.nextToken() != tok.TT_EOF) {
            if (tok.ttype==tok.TT_NUMBER) {
                pixels[i++] = (short)(((int)tok.nval)&65535);
                if (i%inc==0)
                    IJ.showProgress(0.5+((double)i/size)/2.0);
            }
        }
        IJ.showProgress(1.0);
        return new ShortProcessor(width, height, pixels, null);
    }
    
    String getWord(StreamTokenizer tok) throws IOException {
        while (tok.nextToken() != tok.TT_EOF) {
            if (tok.ttype==tok.TT_WORD)
                return tok.sval;
        }
        return null;
    }

    int getInt(StreamTokenizer tok) throws IOException {
        while (tok.nextToken() != tok.TT_EOF) {
            if (tok.ttype==tok.TT_NUMBER)
                return (int)tok.nval;
        }
        return -1;
    }

}