Support EncodedByteAlign=true for CCITTFaxDecodeFilter with k < 0

DEVSIX-1689

Author: Snipx

io/src/main/java/com/itextpdf/io/IOException.java

@@ -92,6 +92,7 @@ public class IOException extends RuntimeException {
     public static final String ExpectedIhdrMarker = "Expected IHDR marker.";
     public static final String ExpectedJp2hMarker = "Expected JP2H marker.";
     public static final String ExpectedJpMarker = "Expected JP marker.";
+    public static final String ExpectedTrailingZeroBitsForByteAlignedLines = "Expected trailing zero bits for byte-aligned lines";
     public static final String ExtraSamplesAreNotSupported = "Extra samples are not supported.";
     public static final String FdfStartxrefNotFound = "FDF startxref not found.";
     public static final String FirstScanlineMustBe1dEncoded = "First scanline must be 1D encoded.";

io/src/main/java/com/itextpdf/io/codec/TIFFConstants.java

@@ -427,6 +427,10 @@ public class TIFFConstants {
      * data not compressed
      */
     public static final int GROUP4OPT_UNCOMPRESSED = 0x2;
+    /**
+     * fill to byte boundary
+     */
+    public static final int GROUP4OPT_FILLBITS = 0x4;
     /**
      * units of resolutions
      */

io/src/main/java/com/itextpdf/io/codec/TIFFFaxDecoder.java

@@ -941,6 +941,7 @@ public void decodeT6(byte[] buffer,
         // has not been tested due to lack of test images using this optional
 
         uncompressedMode = (int) ((tiffT6Options & 0x02) >> 1);
+        fillBits = (int) ((tiffT6Options & 0x04) >> 2);
 
         // Local cached reference
         int[] cce = currChangingElems;
@@ -971,6 +972,17 @@ public void decodeT6(byte[] buffer,
             // Start decoding the scanline at startX in the raster
             bitOffset = startX;
 
+            if (fillBits == 1) {
+                // filter shall expect extra 0 bits before each
+                // encoded line so that the line begins on a byte boundary
+                if (bitPointer > 0) {
+                    int bitsLeft = 8 - bitPointer;
+                    if (nextNBits(bitsLeft) != 0) {
+                        throw new IOException(IOException.ExpectedTrailingZeroBitsForByteAlignedLines);
+                    }
+                }
+            }
+
             // Reset search start position for getNextChangingElement
             lastChangingElement = 0;
 

kernel/src/main/java/com/itextpdf/kernel/pdf/filters/CCITTFaxDecodeFilter.java

@@ -100,8 +100,10 @@ public byte[] decode(byte[] b, PdfName filterName, PdfObject decodeParams, PdfDi
             }
         }
         else {
+            long tiffT6Options = 0;
+            tiffT6Options |= byteAlign ? TIFFConstants.GROUP4OPT_FILLBITS : 0;
             TIFFFaxDecoder deca = new TIFFFaxDecoder(1, width, height);
-            deca.decodeT6(outBuf, b, 0, height, 0);
+            deca.decodeT6(outBuf, b, 0, height, tiffT6Options);
         }
         if (!blackIs1) {
             int len = outBuf.length;