android 图片 倒影 算法

int reflectionGap=4

Bitmap originalImage = BitmapFactory.decodeResource(mContext.getResources(), imageId);
int width = originalImage.getWidth();
int height = originalImage.getHeight();

Matrix matrix = new Matrix();
matrix.preScale(1, -1);//把y和-y对调
Bitmap reflectionImage = Bitmap.createBitmap(originalImage, 0,height / 2, width, height / 2, matrix, false);
Bitmap bitmapWithReflection = Bitmap.createBitmap(width,(height + height / 2), Config.ARGB_8888);
Canvas canvas = new Canvas(bitmapWithReflection);
canvas.drawBitmap(originalImage, 0, 0, null);
Paint deafaultPaint = new Paint();
canvas.drawRect(0, height, width, height + reflectionGap, deafaultPaint);
canvas.drawBitmap(reflectionImage, 0, height + reflectionGap, null);
Paint paint = new Paint();
// 抗锯齿的方法
// paint.setAntiAlias(true);

//渐变
LinearGradient shader = new LinearGradient(0,
originalImage.getHeight(), 0,

bitmapWithReflection.getHeight() + reflectionGap,
0x70ffffff, 0x00ffffff, TileMode.CLAMP);
paint.setShader(shader);
paint.setXfermode(new PorterDuffXfermode(Mode.DST_IN));
canvas.drawRect(0, height, width, bitmapWithReflection.getHeight()+ reflectionGap, paint);

//以上已经完成倒影
//以下直接使用
ImageView imageView = new ImageView(mContext);

imageView.setImageBitmap(bitmapWithReflection);