[shotwell] Compose HSV transformations

[Jens Georg <jensgeorg src gnome org>]

commit 6d7373884ba3a055449549c3b6958e60d4fbea13
Author: Jens Georg <mail jensge org>
Date:   Fri Mar 24 22:00:10 2017 +0100

    Compose HSV transformations
    
    This is possible because all work on the light value only an use remapping
    tables, so we can just remap the tables from one operation into the other
    
    Signed-off-by: Jens Georg <mail jensge org>

 src/ColorTransformation.vala |   41 ++++++++++++++++++++++++++---------------
 1 files changed, 26 insertions(+), 15 deletions(-)
---
diff --git a/src/ColorTransformation.vala b/src/ColorTransformation.vala
index 8f20894..43c4841 100644
--- a/src/ColorTransformation.vala
+++ b/src/ColorTransformation.vala
@@ -96,13 +96,12 @@ public struct HSVAnalyticPixel {
         float min_component = float.min(float.min(p.red, p.green), p.blue);
 
         light_value = max_component;
-        saturation = (max_component != 0.0f) ? ((max_component - min_component) /
-            max_component) : 0.0f;
+        var delta = max_component - min_component;
+        saturation = (max_component != 0.0f) ? ((delta) / max_component) : 0.0f;
 
         if (saturation == 0.0f) {
             hue = 0.0f; /* hue is undefined in the zero saturation case */
         } else {
-            float delta = max_component - min_component;
             if (p.red == max_component) {
                 hue = (p.green - p.blue) / delta;
             } else if (p.green == max_component) {
@@ -212,7 +211,8 @@ public struct HSVAnalyticPixel {
 
 public enum CompositionMode {
     NONE,
-    RGB_MATRIX
+    RGB_MATRIX,
+    HSV_LOOKUP
 }
 
 public enum PixelFormat {
@@ -597,13 +597,34 @@ public class RGBTransformation : PixelTransformation {
 }
 
 public abstract class HSVTransformation : PixelTransformation {
+    protected float remap_table[256];
+
     public HSVTransformation(PixelTransformationType type) {
         base(type, PixelFormat.HSV);
     }
-    
+
+    public override CompositionMode get_composition_mode() {
+        return CompositionMode.HSV_LOOKUP;
+    }
+
     public override RGBAnalyticPixel transform_pixel_rgb(RGBAnalyticPixel p) {
         return (transform_pixel_hsv(p.to_hsv())).to_rgb();
     }
+
+    public override void compose_with(PixelTransformation other) {
+        if (other.get_composition_mode() != CompositionMode.HSV_LOOKUP) {
+            error("HSVTransformation: compose_with(): wrong");
+        }
+
+        var hsv_trans = (HSVTransformation) other;
+
+        // We can do this because ALL HSV transformations actually only
+        // operate on the light_value
+        for (var i = 0; i < 256; i++) {
+            var idx = (int) (this.remap_table[i] * 255.0f);
+            this.remap_table[i] = hsv_trans.remap_table[idx].clamp (0.0f, 1.0f);
+        }
+    }
 }
 
 public class TintTransformation : RGBTransformation {
@@ -1250,7 +1271,6 @@ public class IntensityHistogram {
 }
 
 public class ExpansionTransformation : HSVTransformation {
-    private float[] remap_table = null;
     private const float LOW_DISCARD_MASS = 0.02f;
     private const float HIGH_DISCARD_MASS = 0.02f;
 
@@ -1260,8 +1280,6 @@ public class ExpansionTransformation : HSVTransformation {
     public ExpansionTransformation(IntensityHistogram histogram) {
         base(PixelTransformationType.TONE_EXPANSION);
         
-        remap_table = new float[256];
-
         float LOW_KINK_MASS = LOW_DISCARD_MASS;
         low_kink = 0;
         while (histogram.get_cumulative_probability(low_kink) < LOW_KINK_MASS)
@@ -1312,9 +1330,6 @@ public class ExpansionTransformation : HSVTransformation {
     }
 
     private void build_remap_table() {
-        if (remap_table == null)
-            remap_table = new float[256];
-
         float low_kink_f = ((float) low_kink) / 255.0f;
         float high_kink_f = ((float) high_kink) / 255.0f;
 
@@ -1371,7 +1386,6 @@ public class ShadowDetailTransformation : HSVTransformation {
     private const float TONAL_WIDTH = 1.0f;
 
     private float intensity = 0.0f;
-    private float[] remap_table = null;
     
     public const float MIN_PARAMETER = 0.0f;
     public const float MAX_PARAMETER = 32.0f;
@@ -1386,7 +1400,6 @@ public class ShadowDetailTransformation : HSVTransformation {
         HermiteGammaApproximationFunction func =
             new HermiteGammaApproximationFunction(TONAL_WIDTH);
         
-        remap_table = new float[256];
         for (int i = 0; i < 256; i++) {
             float x = ((float) i) / 255.0f;
             float weight = func.evaluate(x);
@@ -1445,7 +1458,6 @@ public class HighlightDetailTransformation : HSVTransformation {
     private const float TONAL_WIDTH = 1.0f;
 
     private float intensity = 0.0f;
-    private float[] remap_table = null;
     
     public const float MIN_PARAMETER = -32.0f;
     public const float MAX_PARAMETER = 0.0f;
@@ -1460,7 +1472,6 @@ public class HighlightDetailTransformation : HSVTransformation {
         HermiteGammaApproximationFunction func =
             new HermiteGammaApproximationFunction(TONAL_WIDTH);
         
-        remap_table = new float[256];
         for (int i = 0; i < 256; i++) {
             float x = ((float) i) / 255.0f;
             float weight = func.evaluate(1.0f - x);