Add pixel test for transparency group compositing
Adds a pixel test that composites a transparency group using either
constant alpha, or a soft mask. This test currently fails if
ProcessTransparency() does not wrap CFX_DIBitmap::MultiplyAlpha() with
UnPreMultiply() and PreMultiply() operations.
Bug: pdfium:1949
Change-Id: Ie9ade84b96f3ed40d36526d4bf4028a85b3d345a
Reviewed-on: https://pdfium-review.googlesource.com/c/pdfium/+/105071
Commit-Queue: K. Moon <kmoon@chromium.org>
Reviewed-by: Nigi <nigi@chromium.org>
diff --git a/testing/resources/pixel/bug_1949.in b/testing/resources/pixel/bug_1949.in
new file mode 100644
index 0000000..5e7afd3
--- /dev/null
+++ b/testing/resources/pixel/bug_1949.in
@@ -0,0 +1,133 @@
+{{header}}
+{{object 1 0}} <<
+ /Type /Catalog
+ /Pages 2 0 R
+>>
+endobj
+{{object 2 0}} <<
+ /Type /Pages
+ /Count 1
+ /Kids [3 0 R]
+>>
+endobj
+{{object 3 0}} <<
+ /Type /Page
+ /Parent 2 0 R
+ /Contents 4 0 R
+ /MediaBox [0 0 44 24]
+ /Resources <<
+ /ExtGState <<
+ /GSHalfAlphaConstant 5 0 R
+ /GSHalfAlphaMask 6 0 R
+ >>
+ /XObject <<
+ /HalfAlphaSquare 8 0 R
+ >>
+ >>
+>>
+endobj
+{{object 4 0}} <<
+ {{streamlen}}
+>>
+stream
+
+% Opaque black background.
+q
+ 0 0 0 rg
+ 0 0 44 24 re
+ f
+Q
+
+% Transparency group drawn with constant alpha.
+q
+ 1 0 0 1 4 4 cm
+ /GSHalfAlphaConstant gs
+
+ /HalfAlphaSquare Do
+Q
+
+% Transparency group drawn with a soft mask.
+q
+ 1 0 0 1 24 4 cm
+ /GSHalfAlphaMask gs
+
+ /HalfAlphaSquare Do
+Q
+
+endstream
+endobj
+
+% Graphics state with a 0.5 non-stroking alpha constant.
+{{object 5 0}} <<
+ /Type /ExtGState
+ /ca 0.5
+>>
+endobj
+
+% Graphics state with a soft mask containing a 0.5 alpha central hole.
+{{object 6 0}} <<
+ /Type /ExtGState
+ /SMask <<
+ /Type /Mask
+ /S /Luminosity
+ /G 7 0 R
+ >>
+>>
+endobj
+{{object 7 0}} <<
+ /Type /XObject
+ /Subtype /Form
+ /BBox [0 0 16 16]
+ /Group <<
+ /Type /Group
+ /S /Transparency
+ /CS /DeviceGray
+ /I true
+ >>
+ {{streamlen}}
+>>
+stream
+q
+ 1 g
+ 0 0 16 16 re
+ f
+
+ 0.5 g
+ 4 4 8 8 re
+ f
+Q
+endstream
+endobj
+
+% Transparency group containing a 0.5 alpha white square.
+{{object 8 0}} <<
+ /Type /XObject
+ /Subtype /Form
+ /BBox [0 0 16 16]
+ /Group <<
+ /Type /Group
+ /S /Transparency
+ /I true
+ >>
+ /Resources <<
+ /ExtGState <<
+ /GSHalfAlphaConstant 5 0 R
+ >>
+ >>
+ {{streamlen}}
+>>
+stream
+q
+ /GSHalfAlphaConstant gs
+
+ 1 1 1 rg
+ 0 0 16 16 re
+ f
+Q
+endstream
+endobj
+
+{{xref}}
+{{trailer}}
+{{startxref}}
+%%EOF
diff --git a/testing/resources/pixel/bug_1949_expected.pdf.0.png b/testing/resources/pixel/bug_1949_expected.pdf.0.png
new file mode 100644
index 0000000..c215044
--- /dev/null
+++ b/testing/resources/pixel/bug_1949_expected.pdf.0.png
Binary files differ
