Android开发中MaskFilter(面具)的基本用法（总结）

一般两种：BlurMaskFilter（模糊效果）和EmbossMaskFilter（浮雕效果），可以让图片更有立体感。

效果图如下：

activity_main.xml代码如下：

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    android:layout_gravity="center_horizontal"
    xmlns:android="http://schemas.android.com/apk/res/android">

    <!--<ImageView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:src="@mipmap/meizi"/>-->

    <com.deepreality.maskfilterdemo.BlurMaskFilterView
        android:id="@+id/main_BlurMaskFilterView"
        android:layout_width="match_parent"
        android:layout_height="wrap_content">

    </com.deepreality.maskfilterdemo.BlurMaskFilterView>

    <!--<com.deepreality.maskfilterdemo.EmbossMaskFilterView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content" />-->

</LinearLayout>

BlurMaskFilter.java的代码如下：

package com.deepreality.maskfilterdemo;

import android.content.Context;
import android.graphics.BlurMaskFilter;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.support.annotation.Nullable;
import android.util.AttributeSet;
import android.view.View;

/**
 * 模糊效果View
 */
public class BlurMaskFilterView extends View {

    private Paint mPaint;

    public BlurMaskFilterView(Context context) {
        super(context);
        PaintInit();
    }

    public BlurMaskFilterView(Context context, @Nullable AttributeSet attrs) {
        super(context, attrs);
        PaintInit();
    }

    public BlurMaskFilterView(Context context, @Nullable AttributeSet attrs, int defStyleAttr) {
        super(context, attrs, defStyleAttr);
        PaintInit();
    }

    private void PaintInit() {
        mPaint = new Paint();
        mPaint.setAntiAlias(true);          //抗锯齿
        mPaint.setColor(Color.RED);//画笔颜色
        mPaint.setStyle(Paint.Style.FILL);  //画笔风格
        mPaint.setTextSize(68);             //绘制文字大小，单位px
        mPaint.setStrokeWidth(5);           //画笔粗细
    }

    @Override
    protected void onDraw(Canvas canvas) {
        /*//标准模式
        BlurMaskFilter blurMaskFilter1 = new BlurMaskFilter(10f, BlurMaskFilter.Blur.NORMAL);
        mPaint.setMaskFilter(blurMaskFilter1);
        canvas.drawText("目前最喜欢的是Android开发！", 100, 100, mPaint);*/

        /*//外模糊模式
        BlurMaskFilter blurMaskFilter2 = new BlurMaskFilter(10f, BlurMaskFilter.Blur.OUTER);
        mPaint.setMaskFilter(blurMaskFilter2);
        canvas.drawText("目前最喜欢的是Android开发！", 100, 200, mPaint);*/

        /*//内模糊模式
        BlurMaskFilter blurMaskFilter3 = new BlurMaskFilter(10f, BlurMaskFilter.Blur.INNER);
        mPaint.setMaskFilter(blurMaskFilter3);
        canvas.drawText("目前最喜欢的是Android开发！", 100, 300, mPaint);*/

        //内部加粗，外部模糊
        BlurMaskFilter blurMaskFilter4 = new BlurMaskFilter(10f, BlurMaskFilter.Blur.SOLID);
        mPaint.setMaskFilter(blurMaskFilter4);
        canvas.drawText("目前最喜欢的是Android开发！", 100, 400, mPaint);

        //关闭硬件加速
        setLayerType(View.LAYER_TYPE_SOFTWARE, null);
    }
}

EmbossMaskFilter.java的代码如下：

package com.deepreality.maskfilterdemo;

import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.EmbossMaskFilter;
import android.graphics.Paint;
import android.util.AttributeSet;
import android.view.View;

/**
 * 浮雕效果View
 */
public class EmbossMaskFilterView extends View {

    public EmbossMaskFilterView(Context context) {
        super(context);
    }

    public EmbossMaskFilterView(Context context, AttributeSet attrs) {
        super(context, attrs);
    }

    public EmbossMaskFilterView(Context context, AttributeSet attrs, int defStyleAttr) {
        super(context, attrs, defStyleAttr);
    }

    @Override
    protected void onDraw(Canvas canvas) {
        float[] direction = new float[]{ 1, 1, 3 };   // 设置光源的方向
        float light = 0.4f;     //设置环境光亮度
        float specular = 8;     // 定义镜面反射系数
        float blur = 3.0f;      //模糊半径
        EmbossMaskFilter emboss = new EmbossMaskFilter(direction,light,specular,blur);

        Paint paint = new Paint();
        paint.setAntiAlias(true);          //抗锯齿
        paint.setColor(Color.BLUE);//画笔颜色
        paint.setStyle(Paint.Style.FILL);  //画笔风格
        paint.setTextSize(70);             //绘制文字大小，单位px
        paint.setStrokeWidth(8);           //画笔粗细
        paint.setMaskFilter(emboss);

        paint.setMaskFilter(emboss);
        canvas.drawText("这是一张漂亮妹子的图片", 50, 100, paint);

        Bitmap bitmap = BitmapFactory.decodeResource(getResources(), R.mipmap.meizi);
        canvas.drawBitmap(bitmap, 150, 200, paint);

        //关闭硬件加速
        setLayerType(View.LAYER_TYPE_SOFTWARE, null);
    }
}

注意事项

在使用MaskFilter的时候要注意，当我们的targetSdkVersion >= 14的时候，MaskFilter 就不会起效果了，这是因为Android在API 14以上版本都是默认开启硬件加速的，这样充分利用GPU的特性，使得绘画更加平滑，但是会多消耗一些内存！好吧，我们把硬件加速关了就好，可以在不同级别下打开或者关闭硬件加速，一般是关闭~

Application：在配置文件的application节点添加： android:hardwareAccelerated="true"

Activity：在配置文件的activity节点添加 android:hardwareAccelerated="false"

View：可以获得View对象后调用，或者直接在View的onDraw()方法里设置： view.setLayerType(View.LAYER_TYPE_HARDWARE, null);