RFR: 8244718: J2DDemo - AlphaComposite tab - output colors are different with AA & non-AA

[Denis Konoplev]

A straight forward approach to handle blending modes.

Fixes those bugs
- https://bugs.openjdk.java.net/browse/JDK-8244718
- https://bugs.openjdk.java.net/browse/JDK-8251032
- https://bugs.openjdk.java.net/browse/JDK-8253992

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Commit messages:
 - 8244718: J2DDemo - AlphaComposite tab - output colors are different with AA & non-AA

Changes: https://git.openjdk.java.net/lanai/pull/120/files
 Webrev: https://webrevs.openjdk.java.net/?repo=lanai&pr=120&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8244718
  Stats: 205 lines in 2 files changed: 44 ins; 148 del; 13 mod
  Patch: https://git.openjdk.java.net/lanai/pull/120.diff
  Fetch: git fetch https://git.openjdk.java.net/lanai pull/120/head:pull/120

PR: https://git.openjdk.java.net/lanai/pull/120