From 98cb02ee30f8f58bc3a73f2793d4266becfe1967 Mon Sep 17 00:00:00 2001
From: Mark Taylor <m.b.taylor@bristol.ac.uk>
Date: Thu, 30 Jan 2014 10:56:41 +0000
Subject: [PATCH] ttools: add transparency config item for histogram layer

---
 .../main/uk/ac/starlink/ttools/plot2/config/StyleKeys.java | 6 ++++++
 .../ac/starlink/ttools/plot2/layer/HistogramPlotter.java   | 7 ++++++-
 2 files changed, 12 insertions(+), 1 deletion(-)

diff --git a/ttools/src/main/uk/ac/starlink/ttools/plot2/config/StyleKeys.java b/ttools/src/main/uk/ac/starlink/ttools/plot2/config/StyleKeys.java
index 67cfec9fc8..b0104eff0e 100644
--- a/ttools/src/main/uk/ac/starlink/ttools/plot2/config/StyleKeys.java
+++ b/ttools/src/main/uk/ac/starlink/ttools/plot2/config/StyleKeys.java
@@ -90,6 +90,12 @@ public Specifier<Integer> createSpecifier() {
        .createSliderKey( new ConfigMeta( "translevel", "Transparency Level" ),
                          0.1, 0.001, 2, true );
 
+    /** Config key for "normal" transparency - it's just 1-alpha. */
+    public static final ConfigKey<Double> TRANSPARENCY =
+        DoubleConfigKey.createSliderKey( new ConfigMeta( "transparency",
+                                                         "Transparency" ),
+                                         0, 0, 1, false );
+
     /** Config key for line thickness. */
     private static final ConfigKey<Integer> THICKNESS = createThicknessKey( 1 );
 
diff --git a/ttools/src/main/uk/ac/starlink/ttools/plot2/layer/HistogramPlotter.java b/ttools/src/main/uk/ac/starlink/ttools/plot2/layer/HistogramPlotter.java
index 23ae664401..6da41bb0cd 100644
--- a/ttools/src/main/uk/ac/starlink/ttools/plot2/layer/HistogramPlotter.java
+++ b/ttools/src/main/uk/ac/starlink/ttools/plot2/layer/HistogramPlotter.java
@@ -117,6 +117,7 @@ public CoordGroup getCoordGroup() {
     public ConfigKey[] getStyleKeys() {
         return new ConfigKey[] {
             StyleKeys.COLOR,
+            StyleKeys.TRANSPARENCY,
             BinSizer.BINSIZER_KEY,
             CUMULATIVE_KEY,
             NORM_KEY,
@@ -128,7 +129,11 @@ public ConfigKey[] getStyleKeys() {
     }
 
     public HistoStyle createStyle( ConfigMap config ) {
-        Color color = config.get( StyleKeys.COLOR );
+        Color baseColor = config.get( StyleKeys.COLOR );
+        double alpha = 1 - config.get( StyleKeys.TRANSPARENCY );
+        float[] rgba = baseColor.getRGBComponents( new float[ 4 ] );
+        rgba[ 3 ] *= alpha;
+        Color color = new Color( rgba[ 0 ], rgba[ 1 ], rgba[ 2 ], rgba[ 3 ] );
         BarStyle.Form barForm = config.get( StyleKeys.BAR_FORM );
         BarStyle.Placement placement = BarStyle.PLACE_OVER;
         boolean cumulative = config.get( CUMULATIVE_KEY );