笔记14 | 图片倒影+渐变效果

public class MainActivity extends Activity {      private ImageView mRevertImageView;      private Bitmap mSourceBitmap;  //原图      private Bitmap mRevertBitmap;  //倒立图      @Override      protected void onCreate(Bundle savedInstanceState) {          super.onCreate(savedInstanceState);          setContentView(R.layout.activity_main);          mRevertImageView = (ImageView)findViewById(R.id.im_revert);          mSourceBitmap = BitmapFactory.decodeResource(getResources(), R.drawable.source);          mRevertImageView.setBackground(new BitmapDrawable(getResources(), revertBitmap(mSourceBitmap)));      }      private Bitmap revertBitmap(Bitmap originalImage) {          final int reflectionGap = 4;        int width = originalImage.getWidth();         int height = originalImage.getHeight();        Matrix matrix = new Matrix();         matrix.preScale(1, -1); //实现图片的反转        Bitmap reflectionImage = Bitmap.createBitmap(originalImage, 0, height / 2, width, height / 2, matrix, false); //创建反转后的图片Bitmap对象，图片高是原图的一半。        Bitmap bitmapWithReflection = Bitmap.createBitmap(width,             (height + height / 2), Config.ARGB_8888); //创建标准的Bitmap对象，宽和原图一致，高是原图的1.5倍。        Canvas canvas = new Canvas(bitmapWithReflection);        canvas.drawBitmap(originalImage, 0, 0, null); //创建画布对象，将原图画于画布，起点是原点位置。        Paint defaultPaint = new Paint();         canvas.drawRect(0, height, width, height + reflectionGap, defaultPaint);        canvas.drawBitmap(reflectionImage, 0, height + reflectionGap, null);//将反转后的图片画到画布中。        Paint paint = new Paint();         LinearGradient shader = new LinearGradient(0,             originalImage.getHeight(), 0, bitmapWithReflection.getHeight()                     + reflectionGap, 0×70ffffff, 0×00ffffff,             TileMode.MIRROR); //创建线性渐变LinearGradient 对象。        paint.setShader(shader);        paint.setXfermode(new PorterDuffXfermode(Mode.DST_IN));        canvas.drawRect(0, height, width, bitmapWithReflection.getHeight()             + reflectionGap, paint); //画布画出反转图片大小区域，然后把渐变效果加到其中，就出现了图片的倒影效果。        return bitmapWithReflection;     }  }