From 18dbaee9bdfa63ef2c1c3b232d7a309704f9fdf4 Mon Sep 17 00:00:00 2001
From: ask <ask@lazarus-ide.org>
Date: Sun, 17 Oct 2010 09:05:09 +0000
Subject: [PATCH] TAChart: Add InterpolateRGB utility function

git-svn-id: trunk@27736 -
---
 components/tachart/tachartutils.pas   | 16 ++++++++++++++++
 components/tachart/test/UtilsTest.pas | 27 ++++++++++++++++++++++++++-
 2 files changed, 42 insertions(+), 1 deletion(-)

diff --git a/components/tachart/tachartutils.pas b/components/tachart/tachartutils.pas
index 363b4620a7..2903639c83 100644
--- a/components/tachart/tachartutils.pas
+++ b/components/tachart/tachartutils.pas
@@ -219,6 +219,8 @@ procedure ExpandRect(var ARect: TDoubleRect; const APoint: TDoublePoint); inline
 
 function GetIntervals(AMin, AMax: Double; AInverted: Boolean): TDoubleDynArray;
 
+function InterpolateRGB(AColor1, AColor2: Integer; ACoeff: Double): Integer;
+
 function IsPointOnLine(const AP, A1, A2: TPoint): Boolean; inline;
 function IsPointInPolygon(
   const AP: TPoint; const APolygon: array of TPoint): Boolean;
@@ -478,6 +480,20 @@ begin
   end;
 end;
 
+function InterpolateRGB(AColor1, AColor2: Integer; ACoeff: Double): Integer;
+type
+  TBytes = packed array [1..4] of Byte;
+var
+  c1: TBytes absolute AColor1;
+  c2: TBytes absolute AColor2;
+  r: TBytes absolute Result;
+  i: Integer;
+begin
+  ACoeff := EnsureRange(ACoeff, 0.0, 1.0);
+  for i := 1 to 4 do
+    r[i] := Round(c1[i]  + (c2[i] - c1[i]) * ACoeff);
+end;
+
 function IsPointOnLine(const AP, A1, A2: TPoint): Boolean;
 begin
   Result := IsPointInRect(AP, A1, A2) and (PointLineSide(AP, A1, A2) = 0);
diff --git a/components/tachart/test/UtilsTest.pas b/components/tachart/test/UtilsTest.pas
index 339e9b6bdf..4da00672aa 100644
--- a/components/tachart/test/UtilsTest.pas
+++ b/components/tachart/test/UtilsTest.pas
@@ -55,6 +55,14 @@ type
     procedure TestPolygonIntersectsPolygon;
   end;
 
+  { TColorTest }
+
+  TColorTest = class(TTestCase)
+  private
+    procedure AssertEqualsHex(Expected, Actual: Integer); overload;
+  published
+    procedure TestInterpolate;
+  end;
 
 implementation
 
@@ -256,9 +264,26 @@ begin
   AssertFalse(IsPolygonIntersectsPolygon(p1, OffsetPolygon(p1, Point(0, -6))));
 end;
 
+{ TColorTest }
+
+procedure TColorTest.AssertEqualsHex(Expected, Actual: Integer);
+begin
+  AssertTrue(
+    ComparisonMsg(IntToHex(Expected, 8), IntToHex(Actual, 8)),
+    Expected = Actual);
+end;
+
+procedure TColorTest.TestInterpolate;
+begin
+  AssertEqualsHex($01020304, InterpolateRGB($01020304, $00787980, 0.0));
+  AssertEqualsHex($00787980, InterpolateRGB($01020304, $00787980, 1.0));
+  AssertEqualsHex($003D3E42, InterpolateRGB($01020304, $00787980, 0.5));
+  AssertEqualsHex($01010102, InterpolateRGB($01010100, $02020214, 0.1));
+end;
+
 initialization
 
-  RegisterTests([TIntervalListTest, TGeometryTest]);
+  RegisterTests([TIntervalListTest, TGeometryTest, TColorTest]);
 
 end.