make the brightness value user selectable via a seekbar

README

@@ -0,0 +1,5 @@
+Same Android project on how to implement an image filter in C using the Android NDK.
+
+A basic Activity will adjust the brightness level of a bitmap according to user value.
+
+Use the slider to select a brightness value that will be bounded from 1-10 and then click on the button to apply the brightness filter.

gen/com/example/R.java

@@ -16,6 +16,8 @@ public static final class drawable {
     public static final class id {
         public static final int button=0x7f050001;
         public static final int imageView=0x7f050000;
+        public static final int label=0x7f050003;
+        public static final int seekBar=0x7f050002;
     }
     public static final class layout {
         public static final int main=0x7f030000;

jni/imageprocessing.c

@@ -21,10 +21,10 @@ static int rgb_clamp(int value) {
   return value;
 }
 
-static void brightness(AndroidBitmapInfo* info, void* pixels){
+static void brightness(AndroidBitmapInfo* info, void* pixels, float brightnessValue){
 	int xx, yy, red, green, blue, L;
 	uint32_t* line;
-	float brightness = 1.6;
+  //float brightness = 1.6;
 
 	for(yy = 0; yy < info->height; yy++){
 			line = (uint32_t*)pixels;
@@ -36,9 +36,9 @@ static void brightness(AndroidBitmapInfo* info, void* pixels){
 				blue = (int) (line[xx] & 0x00000FF );
 
         //manipulate each value
-        red = rgb_clamp((int)(red * brightness));
-        green = rgb_clamp((int)(green * brightness));
-        blue = rgb_clamp((int)(blue * brightness));
+        red = rgb_clamp((int)(red * brightnessValue));
+        green = rgb_clamp((int)(green * brightnessValue));
+        blue = rgb_clamp((int)(blue * brightnessValue));
 
         // set the new pixel back in
         line[xx] =
@@ -51,7 +51,7 @@ static void brightness(AndroidBitmapInfo* info, void* pixels){
 		}
 }
 
-JNIEXPORT void JNICALL Java_com_example_ImageActivity_brightness(JNIEnv * env, jobject  obj, jobject bitmap)
+JNIEXPORT void JNICALL Java_com_example_ImageActivity_brightness(JNIEnv * env, jobject  obj, jobject bitmap, jfloat brightnessValue)
 {
 
     AndroidBitmapInfo  info;
@@ -71,7 +71,7 @@ JNIEXPORT void JNICALL Java_com_example_ImageActivity_brightness(JNIEnv * env, j
         LOGE("AndroidBitmap_lockPixels() failed ! error=%d", ret);
     }
 
-    brightness(&info,pixels);
+    brightness(&info,pixels, brightnessValue);
 
     AndroidBitmap_unlockPixels(env, bitmap);
 }

res/layout/main.xml

@@ -6,16 +6,32 @@
     >
   <ImageView
     android:id="@+id/imageView"
-    android:layout_width="600px" 
-    android:layout_height="400px" 
+    android:layout_width="400px"
+    android:layout_height="266px"
     />
 
   <Button
    android:id="@+id/button"
    android:layout_width="fill_parent"
    android:layout_height="wrap_content"
    android:text="Adjust Brightness"
-
     />
+
+  <SeekBar
+    android:id="@+id/seekBar"
+    android:layout_width="fill_parent"
+    android:layout_height="wrap_content"
+    android:max="100"
+  />
+
+  <TextView
+    android:id="@+id/label"
+    android:layout_width="fill_parent"
+    android:layout_height="wrap_content"
+    android:text=""
+  />
+
+
 </LinearLayout>
 
+

src/com/example/ImageActivity.java

@@ -7,11 +7,17 @@
 import android.view.View;
 import android.widget.Button;
 import android.widget.ImageView;
+import android.widget.SeekBar;
+import android.widget.TextView;
 
 public class ImageActivity extends Activity {
   private ImageView imageView;
   private Bitmap bitmap;
   private Button button;
+  private SeekBar seekBar;
+  private float brightness;
+  private TextView label;
+  private Bitmap original;
 
   static {
     System.loadLibrary("imageprocessing");
@@ -21,22 +27,36 @@ public class ImageActivity extends Activity {
   public void onCreate(Bundle savedInstanceState) {
     super.onCreate(savedInstanceState);
     setContentView(R.layout.main);
-    bitmap = BitmapFactory.decodeResource(getResources(), R.drawable.wallace);
+    original = BitmapFactory.decodeResource(getResources(), R.drawable.wallace);
 
     imageView = (ImageView) findViewById(R.id.imageView);
     button = (Button) findViewById(R.id.button);
+    seekBar = (SeekBar) findViewById(R.id.seekBar);
+    label = (TextView) findViewById(R.id.label);
+
     button.setOnClickListener(new View.OnClickListener() {
       @Override
       public void onClick(View view) {
         adjustBrightness();
       }
     });
+
+    seekBar.setOnSeekBarChangeListener( new SeekBar.OnSeekBarChangeListener() {
+      public void onProgressChanged(SeekBar seekBar, int progress, boolean fromUser) {
+        brightness = (float)(progress / 10.0f);
+        label.setText("Brightness = " + brightness);
+      }
+
+      public void onStartTrackingTouch(SeekBar seekBar) {}
+      public void onStopTrackingTouch(SeekBar seekBar){}
+    });    
   }
 
   private void adjustBrightness() {
-    brightness(bitmap);
+    Bitmap bitmap = original.copy(Bitmap.Config.ARGB_8888, true);
+    brightness(bitmap, brightness);
     imageView.setImageBitmap(bitmap);
   }
 
-  public native void brightness(Bitmap bmp);
+  public native void brightness(Bitmap bmp, float brightness);
 }