From d9779744f9e1e7211933e12701a05c80c93c9de2 Mon Sep 17 00:00:00 2001
From: Glenn Randers-Pehrson <glennrp at users.sourceforge.net>
Date: Wed, 29 Jun 2016 21:52:53 -0500
Subject: [PATCH] [libpng16] Optimized absolute value calculation in filter
 selection, similar to

code in the PAETH decoder in pngrutil.c. Build with PNG_USE_ABS to use this.
---
 ANNOUNCE   |  7 +++++--
 CHANGES    |  5 ++++-
 pngwutil.c | 32 ++++++++++++++++++++++++++++++++
 3 files changed, 41 insertions(+), 3 deletions(-)

diff --git a/ANNOUNCE b/ANNOUNCE
index 47a0f16e1..c8a350126 100644
--- a/ANNOUNCE
+++ b/ANNOUNCE
@@ -1,4 +1,4 @@
-Libpng 1.6.24beta03 - June 23, 2016
+Libpng 1.6.24beta03 - June 30, 2016
 
 This is not intended to be a public release.  It will be replaced
 within a few weeks by a public version or by another test version.
@@ -67,7 +67,10 @@ Version 1.6.24beta02 [June 23, 2016]
     structure padding is fixable, but it would be a signficant change (moving
     structure members around).
 
-Version 1.6.24beta03 [June 23, 2016]
+Version 1.6.24beta03 [June 30, 2016]
+  Optimized absolute value calculation in filter selection, similar to
+    code in the PAETH decoder in pngrutil.c. Build with PNG_USE_ABS to
+    use this.
 
 Send comments/corrections/commendations to png-mng-implement at lists.sf.net
 (subscription required; visit
diff --git a/CHANGES b/CHANGES
index d3980d3ca..78a899b0c 100644
--- a/CHANGES
+++ b/CHANGES
@@ -5638,7 +5638,10 @@ Version 1.6.24beta02 [June 23, 2016]
     structure padding is fixable, but it would be a signficant change (moving
     structure members around).
 
-Version 1.6.24beta03 [June 23, 2016]
+Version 1.6.24beta03 [June 30, 2016]
+  Optimized absolute value calculation in filter selection, similar to
+    code in the PAETH decoder in pngrutil.c. Build with PNG_USE_ABS to
+    use this.
 
 Send comments/corrections/commendations to png-mng-implement at lists.sf.net
 (subscription required; visit
diff --git a/pngwutil.c b/pngwutil.c
index ddac9bfba..1f7ec5289 100644
--- a/pngwutil.c
+++ b/pngwutil.c
@@ -2262,14 +2262,22 @@ png_setup_sub_row(png_structrp png_ptr, const png_uint_32 bpp,
         i++, rp++, dp++)
    {
       v = *dp = *rp;
+#ifdef PNG_USE_ABS
+      sum += 128 - abs(v - 128);
+#else
       sum += (v < 128) ? v : 256 - v;
+#endif
    }
 
    for (lp = png_ptr->row_buf + 1; i < row_bytes;
       i++, rp++, lp++, dp++)
    {
       v = *dp = (png_byte)(((int)*rp - (int)*lp) & 0xff);
+#ifdef PNG_USE_ABS
+      sum += 128 - abs(v - 128);
+#else
       sum += (v < 128) ? v : 256 - v;
+#endif
 
       if (sum > lmins)  /* We are already worse, don't continue. */
         break;
@@ -2294,7 +2302,11 @@ png_setup_up_row(png_structrp png_ptr, const png_size_t row_bytes,
        i++, rp++, pp++, dp++)
    {
       v = *dp = (png_byte)(((int)*rp - (int)*pp) & 0xff);
+#ifdef PNG_USE_ABS
+      sum += 128 - abs(v - 128);
+#else
       sum += (v < 128) ? v : 256 - v;
+#endif
 
       if (sum > lmins)  /* We are already worse, don't continue. */
         break;
@@ -2319,7 +2331,11 @@ png_setup_avg_row(png_structrp png_ptr, const png_uint_32 bpp,
    {
       v = *dp++ = (png_byte)(((int)*rp++ - ((int)*pp++ / 2)) & 0xff);
 
+#ifdef PNG_USE_ABS
+      sum += 128 - abs(v - 128);
+#else
       sum += (v < 128) ? v : 256 - v;
+#endif
    }
 
    for (lp = png_ptr->row_buf + 1; i < row_bytes; i++)
@@ -2327,7 +2343,11 @@ png_setup_avg_row(png_structrp png_ptr, const png_uint_32 bpp,
       v = *dp++ = (png_byte)(((int)*rp++ - (((int)*pp++ + (int)*lp++) / 2))
           & 0xff);
 
+#ifdef PNG_USE_ABS
+      sum += 128 - abs(v - 128);
+#else
       sum += (v < 128) ? v : 256 - v;
+#endif
 
       if (sum > lmins)  /* We are already worse, don't continue. */
         break;
@@ -2352,7 +2372,11 @@ png_setup_paeth_row(png_structrp png_ptr, const png_uint_32 bpp,
    {
       v = *dp++ = (png_byte)(((int)*rp++ - (int)*pp++) & 0xff);
 
+#ifdef PNG_USE_ABS
+      sum += 128 - abs(v - 128);
+#else
       sum += (v < 128) ? v : 256 - v;
+#endif
    }
 
    for (lp = png_ptr->row_buf + 1, cp = png_ptr->prev_row + 1; i < row_bytes;
@@ -2381,7 +2405,11 @@ png_setup_paeth_row(png_structrp png_ptr, const png_uint_32 bpp,
 
       v = *dp++ = (png_byte)(((int)*rp++ - p) & 0xff);
 
+#ifdef PNG_USE_ABS
+      sum += 128 - abs(v - 128);
+#else
       sum += (v < 128) ? v : 256 - v;
+#endif
 
       if (sum > lmins)  /* We are already worse, don't continue. */
         break;
@@ -2465,7 +2493,11 @@ png_write_find_filter(png_structrp png_ptr, png_row_infop row_info)
          for (i = 0, rp = row_buf + 1; i < row_bytes; i++, rp++)
          {
             v = *rp;
+#ifdef PNG_USE_ABS
+            sum += 128 - abs(v - 128);
+#else
             sum += (v < 128) ? v : 256 - v;
+#endif
          }
       }