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package com.sun.imageio.plugins.tiff;
import javax.imageio.plugins.tiff.BaselineTIFFTagSet;
import javax.imageio.plugins.tiff.TIFFField;
import javax.imageio.plugins.tiff.TIFFTag;
import java.io.IOException;
import javax.imageio.IIOException;
public class TIFFT6Compressor extends TIFFFaxCompressor {
public TIFFT6Compressor() {
super("CCITT T.6", BaselineTIFFTagSet.COMPRESSION_CCITT_T_6, true);
}
Encode a buffer of data using CCITT T.6 Compression also known as
Group 4 facsimile compression.
Params: - data – The row of data to compress.
- lineStride – Byte step between the same sample in different rows.
- colOffset – Bit offset within first
data[rowOffset]. - width – Number of bits in the row.
- height – Number of rows in the buffer.
- compData – The compressed data.
Returns: The number of bytes saved in the compressed data array.
/**
* Encode a buffer of data using CCITT T.6 Compression also known as
* Group 4 facsimile compression.
*
* @param data The row of data to compress.
* @param lineStride Byte step between the same sample in different rows.
* @param colOffset Bit offset within first {@code data[rowOffset]}.
* @param width Number of bits in the row.
* @param height Number of rows in the buffer.
* @param compData The compressed data.
*
* @return The number of bytes saved in the compressed data array.
*/
public synchronized int encodeT6(byte[] data,
int lineStride,
int colOffset,
int width,
int height,
byte[] compData)
{
//
// ao, a1, a2 are bit indices in the current line
// b1 and b2 are bit indices in the reference line (line above)
// color is the current color (WHITE or BLACK)
//
byte[] refData = null;
int refAddr = 0;
int lineAddr = 0;
int outIndex = 0;
initBitBuf();
//
// Iterate over all lines
//
while(height-- != 0) {
int a0 = colOffset;
int last = a0 + width;
int testbit =
((data[lineAddr + (a0>>>3)]&0xff) >>>
(7-(a0 & 0x7))) & 0x1;
int a1 = testbit != 0 ?
a0 : nextState(data, lineAddr, a0, last);
testbit = refData == null ?
0: ((refData[refAddr + (a0>>>3)]&0xff) >>>
(7-(a0 & 0x7))) & 0x1;
int b1 = testbit != 0 ?
a0 : nextState(refData, refAddr, a0, last);
//
// The current color is set to WHITE at line start
//
int color = WHITE;
while(true) {
int b2 = nextState(refData, refAddr, b1, last);
if(b2 < a1) { // pass mode
outIndex += add2DBits(compData, outIndex, pass, 0);
a0 = b2;
} else {
int tmp = b1 - a1 + 3;
if((tmp <= 6) && (tmp >= 0)) { // vertical mode
outIndex += add2DBits(compData, outIndex, vert, tmp);
a0 = a1;
} else { // horizontal mode
int a2 = nextState(data, lineAddr, a1, last);
outIndex += add2DBits(compData, outIndex, horz, 0);
outIndex += add1DBits(compData, outIndex, a1-a0, color);
outIndex += add1DBits(compData, outIndex, a2-a1, color^1);
a0 = a2;
}
}
if(a0 >= last) {
break;
}
color = ((data[lineAddr + (a0>>>3)]&0xff) >>>
(7-(a0 & 0x7))) & 0x1;
a1 = nextState(data, lineAddr, a0, last);
b1 = nextState(refData, refAddr, a0, last);
testbit = refData == null ?
0: ((refData[refAddr + (b1>>>3)]&0xff) >>>
(7-(b1 & 0x7))) & 0x1;
if(testbit == color) {
b1 = nextState(refData, refAddr, b1, last);
}
}
refData = data;
refAddr = lineAddr;
lineAddr += lineStride;
} // End while(height--)
//
// append eofb
//
outIndex += addEOFB(compData, outIndex);
// Flip the bytes if inverse fill was requested.
if(inverseFill) {
for(int i = 0; i < outIndex; i++) {
compData[i] = TIFFFaxDecompressor.flipTable[compData[i]&0xff];
}
}
return outIndex;
}
public int encode(byte[] b, int off,
int width, int height,
int[] bitsPerSample,
int scanlineStride) throws IOException {
if (bitsPerSample.length != 1 || bitsPerSample[0] != 1) {
throw new IIOException(
"Bits per sample must be 1 for T6 compression!");
}
if (metadata instanceof TIFFImageMetadata) {
TIFFImageMetadata tim = (TIFFImageMetadata)metadata;
long[] options = new long[1];
options[0] = 0;
BaselineTIFFTagSet base = BaselineTIFFTagSet.getInstance();
TIFFField T6Options =
new TIFFField(base.getTag(BaselineTIFFTagSet.TAG_T6_OPTIONS),
TIFFTag.TIFF_LONG,
1,
options);
tim.rootIFD.addTIFFField(T6Options);
}
// See comment in TIFFT4Compressor
int maxBits = 9*((width + 1)/2) + 2;
int bufSize = (maxBits + 7)/8;
bufSize = height*(bufSize + 2) + 12;
byte[] compData = new byte[bufSize];
int bytes = encodeT6(b, scanlineStride, 8*off, width, height,
compData);
stream.write(compData, 0, bytes);
return bytes;
}
}