Bug 559564: Darken images when help is shown in dark mode

Change-Id: I7b5885ea01c8a8f3c43ca80be7114fe1789b31bc

platform/org.eclipse.sdk/book.css

diff --git a/platform/org.eclipse.sdk/book.css b/platform/org.eclipse.sdk/book.css
index f8baf55..0d8370e 100644
--- a/platform/org.eclipse.sdk/book.css
+++ b/platform/org.eclipse.sdk/book.css
@@ -140,5 +140,14 @@
 	a:hover{
 		color: #f0f0f0;
 	}
+	
+	/* darken images to add some comfort while reading in dark theme */
+	img {
+		opacity: .75;
+		transition: opacity .5s ease-in-out;
+	}
+	img:hover {
+		opacity: 1;
+	}
 
 }
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