From a74543a1455cebcab664208841315451537c9ae4 Mon Sep 17 00:00:00 2001
From: Jiri Drbalek <jiri.drbalek@firma.seznam.cz>
Date: Thu, 16 May 2019 22:54:14 +0200
Subject: [PATCH] New raster colorizer modes linear-rgba and linear-bgra

---
 include/mapnik/raster_colorizer.hpp |  4 +++-
 src/raster_colorizer.cpp            | 31 +++++++++++++++++++++++++++++
 2 files changed, 34 insertions(+), 1 deletion(-)

diff --git a/include/mapnik/raster_colorizer.hpp b/include/mapnik/raster_colorizer.hpp
index 18ab8c592..debe9c2bf 100644
--- a/include/mapnik/raster_colorizer.hpp
+++ b/include/mapnik/raster_colorizer.hpp
@@ -61,9 +61,11 @@ class raster;
 enum colorizer_mode_enum : std::uint8_t
 {
     COLORIZER_INHERIT = 0,    //!< The stop inherits the mode from the colorizer
-    COLORIZER_LINEAR = 1,     //!< Linear interpolation between colors
+    COLORIZER_LINEAR = 1,     //!< Linear interpolation between colors, each channel separately
     COLORIZER_DISCRETE = 2,   //!< Single color for stop
     COLORIZER_EXACT = 3,      //!< Only the exact value specified for the stop gets translated, others use the default
+    COLORIZER_LINEAR_RGBA = 4,//!< Linear interpolation between colors, all channels combined as RGBA value
+    COLORIZER_LINEAR_BGRA = 5,//!< Linear interpolation between colors, all channels combined as BGRA value
     colorizer_mode_enum_MAX
 };
 
diff --git a/src/raster_colorizer.cpp b/src/raster_colorizer.cpp
index 237dd9329..3d5737200 100644
--- a/src/raster_colorizer.cpp
+++ b/src/raster_colorizer.cpp
@@ -42,6 +42,8 @@ static const char *colorizer_mode_strings[] = {
     "linear",
     "discrete",
     "exact",
+    "linear-rgba",
+    "linear-bgra",
     ""
 };
 
@@ -257,6 +259,35 @@ unsigned raster_colorizer::get_color(float val) const
 
     }
     break;
+    case COLORIZER_LINEAR_RGBA:
+    {
+        if(nextStopValue == stopValue)
+        {
+            return stopColor.rgba();
+        }
+
+        double fraction = (val - stopValue) / (nextStopValue - stopValue);
+        double colorStart = static_cast<double>(stopColor.rgba());
+        double colorEnd = static_cast<double>(nextStopColor.rgba());
+        outputColor = color(colorStart + fraction * (colorEnd - colorStart));
+    }
+    break;
+    case COLORIZER_LINEAR_BGRA:
+    {
+        if(nextStopValue == stopValue)
+        {
+            return stopColor.rgba();
+        }
+
+        double fraction = (val - stopValue) / (nextStopValue - stopValue);
+        std::swap(stopColor.red_, stopColor.blue_);
+        std::swap(nextStopColor.red_, nextStopColor.blue_);
+        double colorStart = static_cast<double>(stopColor.rgba());
+        double colorEnd = static_cast<double>(nextStopColor.rgba());
+        outputColor = color(colorStart + fraction * (colorEnd - colorStart));
+        std::swap(outputColor.red_, outputColor.blue_);
+    }
+    break;
     case COLORIZER_DISCRETE:
         outputColor = stopColor;
         break;