Added source files (Programmieren Tutorium)

presentations/Programmieren-Tutorium/Tutorium-06/Camera.java

@@ -0,0 +1,89 @@
+/**
+ * This class represents a digital camera with an autofocus feature.
+ *
+ * @author Markus Iser, Martin Thoma
+ *
+ */
+public class Camera {
+    /** This epsilon is used for internal float comparisons. */
+    private static final double EPSILON = 1E-6;
+
+    /** The objective that is currently used by the camera. */
+    private final Objective objective;
+
+    /**
+     * The constructor for objective.
+     *
+     * @param objective
+     *            an objective
+     */
+    public Camera(final Objective objective) {
+        this.objective = objective;
+    }
+
+    /**
+     * Check two doubles for equality.
+     *
+     * @param fp1 first floating point number
+     * @param fp2 second floating point number
+     * @return {@code true} if both floats are equal, otherwise {@code false}
+     */
+    private boolean fpEquals(final double fp1, final double fp2) {
+        return Math.abs(fp1 - fp2) < EPSILON;
+    }
+
+    /**
+     * Determine if the contrast on the left is higher than on the current
+     * position.
+     *
+     * @param objective the objective you are manipulating
+     * @return {@code true} the contrast on the left of the current position is
+     *         higher, otherwise {@code false}
+     */
+    private boolean isLeftContrastHigher(Objective objective) {
+        double contrast = objective.getContrast();
+        objective.stepLeft();
+        double contrastNew = objective.getContrast();
+        objective.stepRight();
+
+        // check if the contrast - according to our EPSILON - is the same
+        if (fpEquals(contrast, contrastNew)) {
+            return false;
+        }
+
+        return contrastNew > contrast;
+    }
+
+    /**
+     * Adjust objective to get the optimum focus. The optimum focus is
+     * determined by the highest contrast.
+     */
+    public void autofocus() {
+        boolean stepLeft;
+        double contrast = objective.getContrast();
+
+        // determine direction
+        stepLeft = isLeftContrastHigher(objective);
+
+        // loop until optimum passed
+        while (objective.getContrast() > contrast
+                && !fpEquals(contrast, objective.getContrast())) {
+            contrast = objective.getContrast();
+            if (stepLeft) {
+                objective.stepLeft();
+            } else {
+                objective.stepRight();
+            }
+        }
+
+        // optional correction-move back
+        if (!fpEquals(contrast, objective.getContrast())) {
+            if (stepLeft) {
+                objective.stepRight();
+            } else {
+                objective.stepLeft();
+            }
+        }
+    }
+}
+