Adds matte effect (fixes #30)

Author: Milchreis

README.md

@@ -44,6 +44,7 @@ The following algorithms are supported in this library. Click on the link to see
  - [Looks](#looks)
    - [Lookup table (LUT)](#lookup-table-image)
    - [Glitch-Effect](#glitch-image)
+   - [Matte-Effect](#matte-effect)
    - [Strokes](#strokes-image)
    - [Dithering](#dithering)
    - [Halftone](#halftone-image)
@@ -242,6 +243,15 @@ PImage processedImage = LUT.apply(image, style);
 PImage processedImage = Glitch.apply(image, intensity, scanlineheight);
 ```
 
+#### Matte effect
+![alt matte-effect](https://github.com/Milchreis/processing-imageprocessing/blob/master/img/matte.png?raw=true)
+```java
+PImage processedImage = Matte.apply(image, 
+    matteIntensity,         // intensity for the lifting blacks between 0 and 255
+    contrastIntensity,      // intensity for the constrast between 0 and 255
+    saturationIntensity);   // change for the saturation between -0.5 and 0.5
+```
+
 #### Strokes image
 ![alt strokes](https://github.com/Milchreis/processing-imageprocessing/blob/master/img/strokes.png?raw=true)
 ```java

examples/MatteExample/MatteExample.pde

@@ -0,0 +1,30 @@
+/* Example for creating a matte effect in the dark areas.
+ * Use the mouse in X-axis (left and right) to change the matte intensity.
+ * Use the mouse in Y-axis (up and down) to change the contrast intensity.
+ * Author: Nick 'Milchreis' Müller
+ */
+
+import milchreis.imageprocessing.*;
+
+PImage image;
+
+void setup() {
+  size(550, 550);
+  // Load image
+  image = loadImage(dataPath("example.jpg"));
+}
+
+void draw() {
+
+  if (mousePressed == true) {
+    image(image, 0, 0);
+
+  } else {
+    int matteIntensity = (int) map(mouseX, 0, width, 0, 50);
+    int contrastIntensity = (int) map(mouseY, 0, height, 0, 50);
+    float saturationIntensity = -0.02;
+
+    PImage processedImage = Matte.apply(image, matteIntensity, contrastIntensity, saturationIntensity);
+    image(processedImage, 0, 0);
+  }
+}

examples/MatteExample/data/example.jpg

@@ -0,0 +1,57 @@
+package milchreis.imageprocessing;
+
+import milchreis.imageprocessing.utils.Tools;
+import processing.core.PImage;
+
+import static processing.core.PApplet.constrain;
+import static processing.core.PApplet.map;
+
+/**
+ * @author milchreis
+ */
+public class Matte {
+
+    public static PImage apply(PImage image, int matteIntensity) {
+    	return apply(image, matteIntensity, 12, -0.02f);
+	}
+
+    public static PImage apply(PImage image, int matteIntensity, int contrastIntensity) {
+        return apply(image, matteIntensity, contrastIntensity, -0.02f);
+    }
+
+    public static PImage apply(PImage image, int matteIntensity, int contrastIntensity, float saturationOffset) {
+
+        int offset = constrain(matteIntensity, 0, 255);
+        contrastIntensity = constrain(contrastIntensity, 0, 255);
+        saturationOffset = constrain(saturationOffset, -0.5f, 0.5f);
+
+        PImage output = image.copy();
+
+        for (int x = 0; x < image.width; x++) {
+            for (int y = 0; y < image.height; y++) {
+
+                int[] rgb = Tools.getColors(image, x, y);
+                float[] hsb = Tools.rgbToHsb(image.get(x, y));
+
+                float strength = constrain((1.0f - (3 * hsb[2])), 0.0f, 1.0f);
+
+                // Raise the dark pixel
+                rgb[0] = (int) constrain(rgb[0] + (strength * offset), 0, 255);
+                rgb[1] = (int) constrain(rgb[1] + (strength * offset), 0, 255);
+                rgb[2] = (int) constrain(rgb[2] + (strength * offset), 0, 255);
+
+                // Raise contrast
+                Contrast.contrastPixel(rgb, Contrast.getContrasCorrectionFactor(contrastIntensity));
+
+                // Lower saturation
+                hsb = Tools.rgbToHsb(rgb);
+                hsb[1] = constrain(hsb[1] + saturationOffset, 0.0f, 1.0f);
+
+                Tools.set(output, x, y, Tools.hsbToRgb(hsb));
+            }
+        }
+
+        return output;
+    }
+
+}