Fix extraction of colour components in CPDF_DIBSource::DownSampleScanline32Bit

testing/resources/bug_554151.in

Index: testing/resources/bug_554151.in
diff --git a/testing/resources/bug_554151.in b/testing/resources/bug_554151.in
new file mode 100644
index 0000000000000000000000000000000000000000..3087159f51a90c105ed57091765689aba98790f8
--- /dev/null
+++ b/testing/resources/bug_554151.in
@@ -0,0 +1,59 @@
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