[Libreoffice-commits] core.git: vcl/source

[Stephan Bergmann (via logerrit)]

 vcl/source/filter/png/PngImageReader.cxx |   11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

New commits:
commit 0387077e6647d7a30fd36d4ec41dfc559afe45c3
Author:     Stephan Bergmann <sbergman at redhat.com>
AuthorDate: Wed Sep 23 12:01:35 2020 +0200
Commit:     Stephan Bergmann <sbergman at redhat.com>
CommitDate: Wed Sep 23 16:13:00 2020 +0200

    Correctly read PNG into bitmaps N32BitTcA... formats (where alpha comes first)
    
    This appears to be a regression introduced with
    86ea64f216819696cd86d1926aff0a138ace2baf "Support for native 32bit Bitmap in VCL
    and SVP (cairo) backend".  It caused CppunitTest_vcl_png_test to fail on
    (big-endian) Linux s390x with
    
    > vcl/qa/cppunit/png/PngFilterTest.cxx:176:PngFilterTest::testPng
    > equality assertion failed
    > - Expected: c[ff000040]
    > - Actual  : c[0000ff40]
    
    where eFormat happens to be ScanlineFormat::N32BitTcArgb, vs.
    ScanlineFormat::N32BitTcBgra on e.g. Linux x86-64 (and which thus didn't notice
    the lack of support for N32BitTcA... formats where alpha goes first instead of
    last).
    
    Change-Id: Id6030468718f6ef831b42f2b5ad7ba2c4c46a805
    Reviewed-on: https://gerrit.libreoffice.org/c/core/+/103240
    Tested-by: Jenkins
    Reviewed-by: Stephan Bergmann <sbergman at redhat.com>

diff --git a/vcl/source/filter/png/PngImageReader.cxx b/vcl/source/filter/png/PngImageReader.cxx
index fae4b29a339a..ab5097bfce2c 100644
--- a/vcl/source/filter/png/PngImageReader.cxx
+++ b/vcl/source/filter/png/PngImageReader.cxx
@@ -187,6 +187,8 @@ bool reader(SvStream& rStream, BitmapEx& rBitmapEx, bool bUseBitmap32)
                     for (auto& rRow : aRows)
                         rRow.resize(aRowSizeBytes, 0);
 
+                    auto const alphaFirst = (eFormat == ScanlineFormat::N32BitTcAbgr
+                                             || eFormat == ScanlineFormat::N32BitTcArgb);
                     for (int pass = 0; pass < nNumberOfPasses; pass++)
                     {
                         for (png_uint_32 y = 0; y < height; y++)
@@ -198,10 +200,17 @@ bool reader(SvStream& rStream, BitmapEx& rBitmapEx, bool bUseBitmap32)
                             for (size_t i = 0; i < aRowSizeBytes; i += 4)
                             {
                                 sal_Int8 alpha = pRow[i + 3];
+                                if (alphaFirst)
+                                {
+                                    pScanline[iColor++] = alpha;
+                                }
                                 pScanline[iColor++] = vcl::bitmap::premultiply(pRow[i + 0], alpha);
                                 pScanline[iColor++] = vcl::bitmap::premultiply(pRow[i + 1], alpha);
                                 pScanline[iColor++] = vcl::bitmap::premultiply(pRow[i + 2], alpha);
-                                pScanline[iColor++] = alpha;
+                                if (!alphaFirst)
+                                {
+                                    pScanline[iColor++] = alpha;
+                                }
                             }
                         }
                     }