From da5c0cf0e2c7378b5b625ecce52b291df49b5158 Mon Sep 17 00:00:00 2001
From: Paul Roit <plroit@gmail.com>
Date: Thu, 13 Nov 2014 09:06:41 +0100
Subject: [PATCH] fixed multi precinct handling in jpx

fixes #5475
---
 src/core/jpx.js | 48 +++++++++++++++++++++++++++++++++---------------
 1 file changed, 33 insertions(+), 15 deletions(-)

diff --git a/src/core/jpx.js b/src/core/jpx.js
index 3c6a210b6..c7e1fd48c 100644
--- a/src/core/jpx.js
+++ b/src/core/jpx.js
@@ -480,6 +480,23 @@ var JpxImage = (function JpxImageClosure() {
     // Section B.6 Division resolution to precincts
     var precinctWidth = 1 << dimensions.PPx;
     var precinctHeight = 1 << dimensions.PPy;
+    // Jasper introduces codeblock groups for mapping each subband codeblocks
+    // to precincts. Precinct partition divides a resolution according to width
+    // and height parameters. The subband that belongs to the resolution level
+    // has a different size than the level, unless it is the zero resolution.
+
+    // From Jasper documentation: jpeg2000.pdf, section K: Tier-2 coding:
+    // The precinct partitioning for a particular subband is derived from a
+    // partitioning of its parent LL band (i.e., the LL band at the next higher
+    // resolution level)... The LL band associated with each resolution level is
+    // divided into precincts... Each of the resulting precinct regions is then
+    // mapped into its child subbands (if any) at the next lower resolution
+    // level. This is accomplished by using the coordinate transformation
+    // (u, v) = (ceil(x/2), ceil(y/2)) where (x, y) and (u, v) are the
+    // coordinates of a point in the LL band and child subband, respectively.
+    var isZeroRes = resolution.resLevel === 0;
+    var precinctWidthInSubband = 1 << (dimensions.PPx + (isZeroRes ? 0 : -1));
+    var precinctHeightInSubband = 1 << (dimensions.PPy + (isZeroRes ? 0 : -1));
     var numprecinctswide = (resolution.trx1 > resolution.trx0 ?
       Math.ceil(resolution.trx1 / precinctWidth) -
       Math.floor(resolution.trx0 / precinctWidth) : 0);
@@ -487,18 +504,15 @@ var JpxImage = (function JpxImageClosure() {
       Math.ceil(resolution.try1 / precinctHeight) -
       Math.floor(resolution.try0 / precinctHeight) : 0);
     var numprecincts = numprecinctswide * numprecinctshigh;
-    var precinctXOffset = Math.floor(resolution.trx0 / precinctWidth) *
-                          precinctWidth;
-    var precinctYOffset = Math.floor(resolution.try0 / precinctHeight) *
-                          precinctHeight;
+
     resolution.precinctParameters = {
-      precinctXOffset: precinctXOffset,
-      precinctYOffset: precinctYOffset,
       precinctWidth: precinctWidth,
       precinctHeight: precinctHeight,
       numprecinctswide: numprecinctswide,
       numprecinctshigh: numprecinctshigh,
-      numprecincts: numprecincts
+      numprecincts: numprecincts,
+      precinctWidthInSubband: precinctWidthInSubband,
+      precinctHeightInSubband: precinctHeightInSubband
     };
   }
   function buildCodeblocks(context, subband, dimensions) {
@@ -525,18 +539,21 @@ var JpxImage = (function JpxImageClosure() {
           tbx1: codeblockWidth * (i + 1),
           tby1: codeblockHeight * (j + 1)
         };
-        // calculate precinct number
-        var pi = Math.floor((codeblock.tbx0 -
-                 precinctParameters.precinctXOffset) /
-                 precinctParameters.precinctWidth);
-        var pj = Math.floor((codeblock.tby0 -
-                 precinctParameters.precinctYOffset) /
-                 precinctParameters.precinctHeight);
-        precinctNumber = pj + pi * precinctParameters.numprecinctswide;
+
         codeblock.tbx0_ = Math.max(subband.tbx0, codeblock.tbx0);
         codeblock.tby0_ = Math.max(subband.tby0, codeblock.tby0);
         codeblock.tbx1_ = Math.min(subband.tbx1, codeblock.tbx1);
         codeblock.tby1_ = Math.min(subband.tby1, codeblock.tby1);
+
+        // Calculate precinct number for this codeblock, codeblock position
+        // should be relative to its subband, use actual dimension and position
+        // See comment about codeblock group width and height
+        var pi = Math.floor((codeblock.tbx0_ - subband.tbx0) /
+          precinctParameters.precinctWidthInSubband);
+        var pj = Math.floor((codeblock.tby0_ - subband.tby0) /
+          precinctParameters.precinctHeightInSubband);
+        precinctNumber = pi + (pj * precinctParameters.numprecinctswide);
+
         codeblock.precinctNumber = precinctNumber;
         codeblock.subbandType = subband.type;
         codeblock.Lblock = 3;
@@ -701,6 +718,7 @@ var JpxImage = (function JpxImageClosure() {
         resolution.try0 = Math.ceil(component.tcy0 / scale);
         resolution.trx1 = Math.ceil(component.tcx1 / scale);
         resolution.try1 = Math.ceil(component.tcy1 / scale);
+        resolution.resLevel = r;
         buildPrecincts(context, resolution, blocksDimensions);
         resolutions.push(resolution);