一个Android实现图片的倒影效果的代码示例

  public static Bitmap createReflectedImage(Bitmap originalImage) {
        final int reflectionGap = 4;
        int width = originalImage.getWidth();
        int height = originalImage.getHeight();
        Matrix matrix = new Matrix();
        matrix.preScale(1, -1);
        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 defaultPaint = new Paint();
        canvas.drawRect(0, height, width, height + reflectionGap, defaultPaint);
        canvas.drawBitmap(reflectionImage, 0, height + reflectionGap, null);
        Paint paint = new Paint();
        LinearGradient shader = new LinearGradient(0,
                originalImage.getHeight(), 0, bitmapWithReflection.getHeight()
                        + reflectionGap, 0×70ffffff, 0×00ffffff,
                TileMode.MIRROR);
        paint.setShader(shader);
        paint.setXfermode(new PorterDuffXfermode(Mode.DST_IN));
        canvas.drawRect(0, height, width, bitmapWithReflection.getHeight()
                + reflectionGap, paint);
        return bitmapWithReflection;
    }

解释一下：
Matrix matrix = new Matrix();
matrix.preScale(1, -1);

实现图片的反转，见Android利用Matrix简单处理图片。
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。
LinearGradient shader = new LinearGradient(0,
originalImage.getHeight(), 0, bitmapWithReflection.getHeight()
+ reflectionGap, 0×70ffffff, 0×00ffffff,

创建线性渐变LinearGradient 对象。
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。