Calibrate works?

lib/opencv_processing/examples/LumaVsGray/LumaVsGray.pde

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+/*
+Luma is a better measure of perceived brightness than 
+the tradition grayscale created by averaging R, G, and B channels.
+This sketch demonstrates converting an image to LAB color space
+and accessign the Luma channel for comparison with the more common
+grayscale version. Uses un-wrapped OpenCV cvtColor() function.
+
+*/
+
+import gab.opencv.*;
+// Import the OpenCV Improc class,
+// it has the cvtColor() function we need.
+import org.opencv.imgproc.Imgproc;
+
+OpenCV opencv;
+PImage colorImage, grayImage;
+
+void setup() {
+  colorImage = loadImage("flashlight.jpg");
+  opencv = new OpenCV(this, colorImage);  
+  size(opencv.width, opencv.height);
+  // Save the gray image so we can compare it to Luma
+  grayImage = opencv.getSnapshot();
+  // Use built-in OpenCV function to conver the color image from BGR to LAB color space.
+  Imgproc.cvtColor(opencv.getColor(), opencv.getColor(), Imgproc.COLOR_BGR2Lab);
+  // Since the channels start out in the order BGRA,
+  // Converting to LAB will put the Luma in the B channel
+  opencv.setGray(opencv.getB());
+}
+
+void draw() {
+  background(0);
+  pushMatrix();
+  scale(0.5);
+  image(colorImage, colorImage.width/2, 0); 
+  image(grayImage, 0, colorImage.height);
+  image(opencv.getOutput(), colorImage.width, colorImage.height);
+  popMatrix();
+
+  fill(255);
+  text("GRAY", 30, height -25);
+  text("LUMA", width/2 + 30, height - 25);
+}