[gs-commits] ghostpdl branch, gs9.28-temp-for-testing, updated. gs9.28-temp-for-testing-tag-7-ga6d0709

The ghostpdl branch, gs9.28-temp-for-testing has been updated
       via  a6d07099578f3a4f9a5aaceb83e944382b93210d (commit)
      from  3b5cffabfad0daa430be50c7c70bc111bf1a9dd2 (commit)

----------------------------------------------------------------------
commit a6d07099578f3a4f9a5aaceb83e944382b93210d
Author: Robin Watts <[email protected]>
Date:   Mon Aug 26 17:02:03 2019 +0100

    Fix deep colour transparency "uncompositing".
    
    Uncompositing a group uses a scale factor that is greater in range
    than we'd like; we need to resort to 64bit to do this to avoid
    losing accuracy.
    
    This solves problems seen in:
    
       tests_private/comparefiles/Bug689918.pdf.psdcmyk16.300.1

diff --git a/base/gxblend.c b/base/gxblend.c
index cf9991b..6d7db5e 100644
--- a/base/gxblend.c
+++ b/base/gxblend.c
@@ -2189,13 +2189,16 @@ art_pdf_recomposite_group_16(uint16_t *gs_restrict *dstp, uint16_t *gs_restrict
                "src = (src, src_alpha_g) over dst" for src */
             scale = ((unsigned int)(dst_alpha * 65535 + (src_alpha_g>>1))) / src_alpha_g -
                 dst_alpha;
+            /* scale is NOT in 16.16 form here. I've seen values of 0xfefe01, for example. */
             for (i = 0; i < n_chan; i++) {
                 int si, di;
+                int64_t tmp64;
 
                 si = src[i];
                 di = dst[i];
-                tmp = (si - di) * scale + 0x8000;
-                tmp = si + (tmp >> 16);
+                /* RJW: Nasty that we have to resort to 64bit here, but we'll live with it. */
+                tmp64 = (si - di) * (int64_t)scale + 0x8000;
+                tmp = si + (tmp64 >> 16);
 
                 /* todo: it should be possible to optimize these cond branches */
                 if (tmp < 0)


Summary of changes:
 base/gxblend.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)