Android给图片添加倒影效果

注释很详细，就不多说了。具体实现代码如下：

package com.example.specialeffect_reflectedimages;

import android.app.Activity;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.graphics.Canvas;
import android.graphics.LinearGradient;
import android.graphics.Matrix;
import android.graphics.Paint;
import android.graphics.PorterDuffXfermode;
import android.graphics.Bitmap.Config;
import android.graphics.PorterDuff.Mode;
import android.graphics.Shader.TileMode;
import android.os.Bundle;
import android.widget.ImageView;

/*
 * 为图片添加倒影
 */

public class MainActivity extends Activity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        Bitmap bitmap = createReflectedBitmap(R.drawable.dog);
        ImageView imageView = (ImageView) findViewById(R.id.ivTest);
        imageView.setImageBitmap(bitmap);
    }

    /**
     * @param imgId 图片资源id
     * @return Bitmap 带倒影的Bitmap
     */
    private Bitmap createReflectedBitmap(int imgId){
        Bitmap originalImage = BitmapFactory.decodeResource(getResources(), imgId);
        // 反射图片和原始图片中间的间距
        final int reflectionGap = 4;
        int width = originalImage.getWidth();
        int height = originalImage.getHeight();

        //通过矩阵对图像进行变换
        Matrix matrix = new Matrix();
        // 第一个参数为1，表示x方向上以原比例为准保持不变，正数表示方向不变。
        // 第二个参数为-1，表示y方向上以原比例为准保持不变，负数表示方向取反。
        matrix.preScale(1, -1); // 实现图片的反转

        // 创建反转后的图片Bitmap对象，图片高是原图的一半
        Bitmap reflectionImage = Bitmap.createBitmap(originalImage, 0,
                height / 2, width, height / 2, matrix, false);

        // 创建标准的Bitmap对象，宽和原图一致，高是原图的1.5倍
        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);
        // 将反转后的图片画到画布中
        canvas.drawBitmap(reflectionImage, 0, height + reflectionGap, null);

        Paint paint = new Paint();
        // 创建线性渐变LinearGradient 对象。
        LinearGradient shader = new LinearGradient(0, originalImage
                .getHeight(), 0, bitmapWithReflection.getHeight()
                + reflectionGap, 0x70ffffff, 0x00ffffff, TileMode.MIRROR);

        paint.setShader(shader);
        // 倒影遮罩效果
        paint.setXfermode(new PorterDuffXfermode(Mode.DST_IN));
        canvas.drawRect(0, height, width, bitmapWithReflection.getHeight()
                + reflectionGap, paint);

        return bitmapWithReflection;
    }
}

布局文件：

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context="${relativePackage}.${activityClass}" >

    <ImageView
        android:id="@+id/ivTest"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:contentDescription="@null"
        android:layout_centerHorizontal="true" />

</RelativeLayout>