Added individual led brightness option to led strip

apa102/src/main/java/com/google/android/things/contrib/driver/apa102/Apa102.java

@@ -67,7 +67,8 @@ public enum Direction {
     private Mode mLedMode;
 
     // RGB LED strip settings that have sensible defaults.
-    private int mLedBrightness = MAX_BRIGHTNESS >> 1; // default to half
+    private int mLedBrightnessGlobal = MAX_BRIGHTNESS >> 1; // Default to half
+    private int mLedBrightness[];
 
     // Direction of the led strip;
     private Direction mDirection;
@@ -162,13 +163,33 @@ public void setBrightness(int ledBrightness) {
             throw new IllegalArgumentException("Brightness needs to be between 0 and "
                     + MAX_BRIGHTNESS);
         }
-        mLedBrightness = ledBrightness;
+        mLedBrightnessGlobal = ledBrightness;
+        mLedBrightness = null;
     }
 
     /**
-     * Get the current brightness level
+     * Sets the brightness for all LEDs in the strip.
+     * @param ledBrightness The brightness of the LED strip, between 0 and {@link #MAX_BRIGHTNESS}.
+     */
+    public void setIndividualBrightness(int[] ledBrightness) {
+        mLedBrightness = new int[ledBrightness.length];
+        for (int i=0; i<ledBrightness.length; i++) {
+            if (ledBrightness[i] < 0 || ledBrightness[i] > MAX_BRIGHTNESS) {
+                throw new IllegalArgumentException("Brightness needs to be between 0 and "
+                        + MAX_BRIGHTNESS);
+            }
+            mLedBrightness[i] = ledBrightness[i];
+        }
+    }
+
+    /**
+     * Get the current brightness
      */
     public int getBrightness() {
+        return mLedBrightnessGlobal;
+    }
+
+    public int[] getIndividualBrightness() {
         return mLedBrightness;
     }
 
@@ -212,9 +233,12 @@ public void write(int[] colors) throws IOException {
         pos += APA_START_FRAME_PACKET_LENGTH;
 
         // Compute the packets to send.
-        byte brightness = (byte) (0xE0 | mLedBrightness); // Less brightness possible
         final Direction currentDirection = mDirection; // Avoids reading changes of mDirection during loop
+        byte brightness = (byte) (0xE0 | mLedBrightnessGlobal); // Default initialization
         for (int i = 0; i < colors.length; i++) {
+            if (mLedBrightness != null) {
+                brightness = (byte) (0xE0 | mLedBrightness[i]); // Less brightness possible
+            }
             int di = currentDirection == Direction.NORMAL ? i : colors.length - i - 1;
             copyApaColorData(brightness, colors[di], mLedMode, mLedData, pos);
             pos += APA_COLOR_PACKET_LENGTH;

apa102/src/test/java/com/google/android/things/contrib/driver/apa102/Apa102Test.java

@@ -88,6 +88,20 @@ public void setBrightness_throwsIfTooLarge() throws IOException {
         leds.setBrightness(Apa102.MAX_BRIGHTNESS + 1);
     }
 
+    @Test
+    public void setBrightnessArray_throwsIfTooSmall() throws IOException {
+        Apa102 leds = new Apa102(mSpiDevice, Apa102.Mode.BGR, Apa102.Direction.NORMAL);
+        mExpectedException.expect(IllegalArgumentException.class);
+        leds.setIndividualBrightness(new int[] {-1});
+    }
+
+    @Test
+    public void setBrightnessArray_throwsIfTooLarge() throws IOException {
+        Apa102 leds = new Apa102(mSpiDevice, Apa102.Mode.BGR, Apa102.Direction.NORMAL);
+        mExpectedException.expect(IllegalArgumentException.class);
+        leds.setIndividualBrightness(new int[] {Apa102.MAX_BRIGHTNESS + 1});
+    }
+
     @Test
     public void setDirection() throws IOException {
         Apa102 leds = new Apa102(mSpiDevice, Apa102.Mode.BGR, Apa102.Direction.NORMAL);