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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;
import javax.imageio.metadata.IIOMetadata;
public class TIFFT4Compressor extends TIFFFaxCompressor {
private boolean is1DMode = false;
private boolean isEOLAligned = false;
public TIFFT4Compressor() {
super("CCITT T.4", BaselineTIFFTagSet.COMPRESSION_CCITT_T_4, true);
}
Sets the value of the metadata field. The implementation in this class also sets local options
from the T4_OPTIONS field if it exists, and if it doesn't, adds
it with default values.
Params: - metadata – the
IIOMetadata object for the image being written.
See Also:
/**
* Sets the value of the {@code metadata} field.
*
* <p> The implementation in this class also sets local options
* from the T4_OPTIONS field if it exists, and if it doesn't, adds
* it with default values.</p>
*
* @param metadata the {@code IIOMetadata} object for the
* image being written.
*
* @see #getMetadata()
*/
public void setMetadata(IIOMetadata metadata) {
super.setMetadata(metadata);
if (metadata instanceof TIFFImageMetadata) {
TIFFImageMetadata tim = (TIFFImageMetadata)metadata;
TIFFField f = tim.getTIFFField(BaselineTIFFTagSet.TAG_T4_OPTIONS);
if (f != null) {
int options = f.getAsInt(0);
is1DMode = (options & 0x1) == 0;
isEOLAligned = (options & 0x4) == 0x4;
} else {
long[] oarray = new long[1];
oarray[0] = (isEOLAligned ? 0x4 : 0x0) |
(is1DMode ? 0x0 : 0x1);
BaselineTIFFTagSet base = BaselineTIFFTagSet.getInstance();
TIFFField T4Options =
new TIFFField(base.getTag(BaselineTIFFTagSet.TAG_T4_OPTIONS),
TIFFTag.TIFF_LONG,
1,
oarray);
tim.rootIFD.addTIFFField(T4Options);
}
}
}
Encode a buffer of data using CCITT T.4 Compression also known as
Group 3 facsimile compression.
Params: - is1DMode – Whether to perform one-dimensional encoding.
- isEOLAligned – Whether EOL bit sequences should be padded.
- 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.4 Compression also known as
* Group 3 facsimile compression.
*
* @param is1DMode Whether to perform one-dimensional encoding.
* @param isEOLAligned Whether EOL bit sequences should be padded.
* @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 int encodeT4(boolean is1DMode,
boolean isEOLAligned,
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 = data;
int lineAddr = 0;
int outIndex = 0;
initBitBuf();
int KParameter = 2;
for(int numRows = 0; numRows < height; numRows++) {
if(is1DMode || (numRows % KParameter) == 0) { // 1D encoding
// Write EOL+1
outIndex += addEOL(is1DMode, isEOLAligned, true,
compData, outIndex);
// Encode row
outIndex += encode1D(data, lineAddr, colOffset, width,
compData, outIndex);
} else { // 2D encoding.
// Write EOL+0
outIndex += addEOL(is1DMode, isEOLAligned, false,
compData, outIndex);
// Set reference to previous line
int refAddr = lineAddr - lineStride;
// Encode row
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[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[refAddr + (b1>>>3)]&0xff) >>>
(7-(b1 & 0x7))) & 0x1;
if(testbit == color) {
b1 = nextState(refData, refAddr, b1, last);
}
}
}
// Skip to next line.
lineAddr += lineStride;
}
for(int i = 0; i < 6; i++) {
outIndex += addEOL(is1DMode, isEOLAligned, true,
compData, outIndex);
}
//
// flush all pending bits
//
while(ndex > 0) {
compData[outIndex++] = (byte)(bits >>> 24);
bits <<= 8;
ndex -= 8;
}
// 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 T4 compression!");
}
// This initial buffer size is based on an alternating 1-0
// pattern generating the most bits when converted to code
// words: 9 bits out for each pair of bits in. So the number
// of bit pairs is determined, multiplied by 9, converted to
// bytes, and a ceil() is taken to account for fill bits at the
// end of each line. The "2" addend accounts for the case
// of the pattern beginning with black. The buffer is intended
// to hold only a single row.
int maxBits = 9*((width + 1)/2) + 2;
int bufSize = (maxBits + 7)/8;
// Calculate the maximum row as the G3-1D size plus the EOL,
// multiply this by the number of rows in the tile, and add
// 6 EOLs for the RTC (return to control).
bufSize = height*(bufSize + 2) + 12;
byte[] compData = new byte[bufSize];
int bytes = encodeT4(is1DMode,
isEOLAligned,
b, scanlineStride, 8*off,
width, height,
compData);
stream.write(compData, 0, bytes);
return bytes;
}
}