需要帮助开始通过Java将原始G3传真文件转换为TIFF格式

它不以任何方式解码G3 / T.4数据,它只是将原始传真数据包装在最小的TIFF容器中.这允许稍后将数据读取为正常TIFF.它使用(我自己的)TwelveMonkeys ImageIO库来实现.

如果您不知道传真文件的宽度/高度,您可以通过使用CCITTFaxDecoderStream,尝试标准中定义的不同宽度(列)来实现算法来查找它们,并查看有多少整行你可以阅读.如果你有正确的数字,你应该完全消耗流.

import com.twelvemonkeys.imageio.metadata.AbstractEntry;
import com.twelvemonkeys.imageio.metadata.Entry;
import com.twelvemonkeys.imageio.metadata.exif.EXIFWriter;
import com.twelvemonkeys.imageio.metadata.exif.Rational;
import com.twelvemonkeys.imageio.metadata.exif.TIFF;

import javax.imageio.ImageIO;
import javax.imageio.stream.ImageOutputStream;
import java.io.*;
import java.util.ArrayList;

public class G3Test {
    public static void main(String[] args) throws IOException {
        File input = new File(args[0]);
        File output = new File(args.length > 1 ? args[1] : input.getName().replace(".g3",".tif"));

        // ImageWidth = 1728,2048,2482. SHORT or LONG. These are the fixed page widths in pixels defined in CCITT Group 3.
        int columns = 1728; // The default
        int rows = 100;     // Trial and error for sample file found at http://www.filesuffix.com/en/extension/fax

        ArrayList<Entry> entries = new ArrayList<>();

        // http://cool.conservation-us.org/bytopic/imaging/std/tiff-f.html
        // Required Class F tags
        entries.add(new TIFFEntry(TIFF.TAG_COMPRESSION,TIFF.TYPE_SHORT,3)); // CCITT T.4
        entries.add(new TIFFEntry(TIFF.TAG_FILL_ORDER,1));  // Left to right
        entries.add(new TIFFEntry(TIFF.TAG_GROUP3OPTIONS,TIFF.TYPE_LONG,0)); // No options set
        entries.add(new TIFFEntry(TIFF.TAG_IMAGE_WIDTH,columns));
        entries.add(new TIFFEntry(TIFF.TAG_IMAGE_HEIGHT,rows));
        entries.add(new TIFFEntry(TIFF.TAG_SUBFILE_TYPE,2)); // Page
        entries.add(new TIFFEntry(TIFF.TAG_RESOLUTION_UNIT,2)); // Inches
        entries.add(new TIFFEntry(TIFF.TAG_X_RESOLUTION,TIFF.TYPE_RATIONAL,new Rational(204))); // 204
        entries.add(new TIFFEntry(TIFF.TAG_Y_RESOLUTION,new Rational(98))); // 98,196
        // Required Bilevel (Class B) tags
        entries.add(new TIFFEntry(TIFF.TAG_BITS_PER_SAMPLE,1)); // 1 bit/sample
        entries.add(new TIFFEntry(TIFF.TAG_PHOTOMETRIC_INTERPRETATION,0)); // White is zero
        entries.add(new TIFFEntry(TIFF.TAG_SOFTWARE,TIFF.TYPE_ASCII,"TwelveMonkeys FAX2TIFF 0.1 BETA ;-)"));
        entries.add(new TIFFEntry(TIFF.TAG_ROWS_PER_STRIP,rows));
        entries.add(new TIFFEntry(TIFF.TAG_SAMPLES_PER_PIXEL,1)); // 1 sample/pixel
        entries.add(new TIFFEntry(TIFF.TAG_STRIP_BYTE_COUNTS,input.length()));
        entries.add(new TIFFEntry(TIFF.TAG_STRIP_OFFSETS,-1)); // placeholder for now

        // We now have all our entries,compute size of the entries,and make that the offset (we'll write the data right after).
        EXIFWriter writer = new EXIFWriter();
        long offset = 12 + writer.computeIFDSize(entries); // + 12 for TIFF magic (4),IFD0 pointer (4) and EOF (4)
        entries.remove(entries.size() - 1);
        entries.add(new TIFFEntry(TIFF.TAG_STRIP_OFFSETS,offset));


        try (InputStream in = new FileInputStream(input)) {
            try (ImageOutputStream out = ImageIO.createImageOutputStream(output)) {
                // Write the TIFF IFD for the image data
                writer.write(entries,out);

                // Copy the already G3 compressed bytes verbatim to the output
                byte[] buffer = new byte[1024];
                int read;
                while ((read = in.read(buffer)) >= 0) {
                    out.write(buffer,read);
                }
            }
        }
    }

    // API stupidity,should be fixed in later verisons (ie. contain a predefined TIFFEntry class)
    static final class TIFFEntry extends AbstractEntry {
        private final short type;

        TIFFEntry(int identifier,short type,Object value) {
            super(identifier,value);
            this.type = type;
        }

        @Override
        public String getTypeName() {
            return TIFF.TYPE_NAMES[type];
        }
    }
}