[gs-commits] ghostpdl branch, master, updated. jbig2dec-0.14-1587-g825f77e

The ghostpdl branch, master has been updated
  discards  390867f19f49a52d4585c0e5e980b2c245e15e76 (commit)
       via  825f77eabdbfaa9d566d38c4b2be918143cd5778 (commit)

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----------------------------------------------------------------------
commit 825f77eabdbfaa9d566d38c4b2be918143cd5778
Author: Robin Watts <[email protected]>
Date:   Tue Aug 20 12:24:03 2019 +0100

    Fix overflow in deep color blending.
    
    Multiplying a 16bit unsigned value with a 16 bit signed value
    in a 32bit int means we lose the sign bit. Sacrifice a bit of
    accuracy to avoid that.

diff --git a/base/gxblend.c b/base/gxblend.c
index 0e29fc9..aaadca8 100644
--- a/base/gxblend.c
+++ b/base/gxblend.c
@@ -1934,6 +1934,8 @@ art_pdf_composite_pixel_alpha_16_inline(uint16_t *gs_restrict dst, uint16_t *gs_
                 dst[i] += (src_scale * (blend[i] - dst[i]) + 0x8000) >> 16;
             }
         } else {
+            int a_b2 = a_b>>1;
+            int ss2 = src_scale>>1;
             for (i = 0; i < first_spot; i++) {
                 int c_bl;		/* Result of blend function */
 
@@ -1941,8 +1943,8 @@ art_pdf_composite_pixel_alpha_16_inline(uint16_t *gs_restrict dst, uint16_t *gs_
                 c_b = dst[i];
                 c_bl = blend[i];
 
-                c_s += (a_b * (c_bl - c_s) + 0x8000) >> 16;
-                c_b += (src_scale * (c_s - c_b) + 0x8000) >> 16;
+                c_s += (a_b2 * (c_bl - c_s) + 0x4000) >> 15;
+                c_b += (ss2 * (c_s - c_b) + 0x4000) >> 15;
                 dst[i] = c_b;
             }
         }


Summary of changes:
 windows/GhostPDL.sln | 19 +++++++------------
 1 file changed, 7 insertions(+), 12 deletions(-)