From 6025b6016517c6d898d8957d1d7e03ba71431912 Mon Sep 17 00:00:00 2001
From: tknall <tknall@7b5415b0-85f9-ee4d-85bd-d5d0c3b42d1c>
Date: Fri, 1 Dec 2006 12:20:24 +0000
Subject: Initial import of release 2.2.

git-svn-id: https://joinup.ec.europa.eu/svn/pdf-as/trunk@4 7b5415b0-85f9-ee4d-85bd-d5d0c3b42d1c
---
 .../pdfbox/pdmodel/graphics/predictor/Paeth.java   | 121 +++++++++++++++++++++
 1 file changed, 121 insertions(+)
 create mode 100644 src/main/java/org/pdfbox/pdmodel/graphics/predictor/Paeth.java

(limited to 'src/main/java/org/pdfbox/pdmodel/graphics/predictor/Paeth.java')

diff --git a/src/main/java/org/pdfbox/pdmodel/graphics/predictor/Paeth.java b/src/main/java/org/pdfbox/pdmodel/graphics/predictor/Paeth.java
new file mode 100644
index 0000000..1fddef0
--- /dev/null
+++ b/src/main/java/org/pdfbox/pdmodel/graphics/predictor/Paeth.java
@@ -0,0 +1,121 @@
+/**
+ * Copyright (c) 2005, www.pdfbox.org
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice,
+ *    this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright notice,
+ *    this list of conditions and the following disclaimer in the documentation
+ *    and/or other materials provided with the distribution.
+ * 3. Neither the name of pdfbox; nor the names of its
+ *    contributors may be used to endorse or promote products derived from this
+ *    software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE FOR ANY
+ * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
+ * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
+ * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON
+ * ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
+ * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ * http://www.pdfbox.org
+ */
+package org.pdfbox.pdmodel.graphics.predictor;
+
+/**
+ * From http://www.w3.org/TR/PNG-Filters.html: The Paeth filter computes a
+ * simple linear function of the three neighboring pixels (left, above, upper
+ * left), then chooses as predictor the neighboring pixel closest to the
+ * computed value. This technique is due to Alan W. Paeth [PAETH].
+ * 
+ * To compute the Paeth filter, apply the following formula to each byte of the
+ * scanline:
+ * 
+ * <code>Paeth(i,j) = Raw(i,j) - PaethPredictor(Raw(i-1,j), Raw(i,j-1), Raw(i-1,j-1))</code>
+ * 
+ * To decode the Paeth filter
+ * 
+ * <code>Raw(i,j) = Paeth(i,j) - PaethPredictor(Raw(i-1,j), Raw(i,j-1), Raw(i-1,j-1))</code>
+ * 
+ * @author xylifyx@yahoo.co.uk
+ * @version $Revision: 1.2 $
+ */
+public class Paeth extends PredictorAlgorithm 
+{
+    /**
+     * The paeth predictor function.
+     * 
+     * This function is taken almost directly from the PNG definition on
+     * http://www.w3.org/TR/PNG-Filters.html
+     * 
+     * @param a
+     *            left
+     * @param b
+     *            above
+     * @param c
+     *            upper left
+     * @return The result of the paeth predictor.
+     */
+    public int paethPredictor(int a, int b, int c) 
+    {
+        int p = a + b - c; // initial estimate
+        int pa = Math.abs(p - a); // distances to a, b, c
+        int pb = Math.abs(p - b);
+        int pc = Math.abs(p - c);
+        // return nearest of a,b,c,
+        // breaking ties in order a,b,c.
+        if (pa <= pb && pa <= pc)
+        {
+            return a;
+        }
+        else if (pb <= pc)
+        {
+            return b;
+        }
+        else
+        {
+            return c;
+        }
+    }
+
+    /**
+     * @see org.pdfbox.pdmodel.graphics.predictor.PredictorAlgorithm#encodeLine(byte[], byte[],
+     *      int, int, int, int)
+     */
+    public void encodeLine(byte[] src, byte[] dest, int srcDy, int srcOffset,
+            int destDy, int destOffset) 
+    {
+        int bpl = getWidth() * getBpp();
+        for (int x = 0; x < bpl; x++) 
+        {
+            dest[x + destOffset] = (byte) (src[x + srcOffset] - paethPredictor(
+                    leftPixel(src, srcOffset, srcDy, x), abovePixel(src,
+                            srcOffset, srcDy, x), aboveLeftPixel(src,
+                            srcOffset, srcDy, x)));
+        }
+    }
+
+    /**
+     * @see org.pdfbox.pdmodel.graphics.predictor.PredictorAlgorithm#decodeLine(byte[], byte[],
+     *      int, int, int, int)
+     */
+    public void decodeLine(byte[] src, byte[] dest, int srcDy, int srcOffset,
+            int destDy, int destOffset) 
+    {
+        int bpl = getWidth() * getBpp();
+        for (int x = 0; x < bpl; x++) 
+        {
+            dest[x + destOffset] = (byte) (src[x + srcOffset] + paethPredictor(
+                    leftPixel(dest, destOffset, destDy, x), abovePixel(dest,
+                            destOffset, destDy, x), aboveLeftPixel(dest,
+                            destOffset, destDy, x)));
+        }
+    }
+}
-- 
cgit v1.2.3