Bitmap之extractAlpha函数抽取alpha值

package com.loaderman.customviewdemo;

import android.app.Activity;

import android.graphics.Bitmap;

import android.graphics.BitmapFactory;

import android.graphics.BlurMaskFilter;

import android.graphics.Canvas;

import android.graphics.Color;

import android.graphics.Paint;

import android.os.Bundle;

import android.widget.ImageView;

public class MainActivity extends Activity {

    @Override

    protected void onCreate(Bundle savedInstanceState) {

        super.onCreate(savedInstanceState);

        setContentView(R.layout.activity_main);

        //基本提取Alpha图像

        baseExtraAlpha();

        //发光效果

        adVanceExtraAlpha();

    }

    //基本提取Alpha图像

    private void baseExtraAlpha() {

        Bitmap srcBmp = BitmapFactory.decodeResource(getResources(), R.drawable.cat_dog);

        Bitmap bitmap = Bitmap.createBitmap(srcBmp.getWidth(), srcBmp.getHeight(), Bitmap.Config.ARGB_8888);

        Canvas canvas = new Canvas(bitmap);

        Paint paint = new Paint();

        paint.setColor(Color.CYAN);

        canvas.drawBitmap(srcBmp.extractAlpha(), 0, 0, paint);

        ImageView iv = (ImageView) findViewById(R.id.img);

        iv.setImageBitmap(bitmap);

        srcBmp.recycle();

    }

    //发光效果

    private void adVanceExtraAlpha() {

        Bitmap srcBmp = BitmapFactory.decodeResource(getResources(), R.drawable.cat_dog);

        //获取Alpha bitmap

        Paint alphaPaint = new Paint();

        BlurMaskFilter blurMaskFilter = new BlurMaskFilter(20, BlurMaskFilter.Blur.NORMAL);

        alphaPaint.setMaskFilter(blurMaskFilter);

        int[] offsetXY = new int[2];

        Bitmap alphaBmp = srcBmp.extractAlpha(alphaPaint, offsetXY);

        //创建Bitmap

        Bitmap bitmap = Bitmap.createBitmap(alphaBmp.getWidth(), alphaBmp.getHeight(), Bitmap.Config.ARGB_8888);

        Canvas canvas = new Canvas(bitmap);

        Paint paint = new Paint();

        paint.setColor(Color.CYAN);

        canvas.drawBitmap(alphaBmp, 0, 0, paint);

        //绘制源图像

        canvas.drawBitmap(srcBmp, -offsetXY[0], -offsetXY[1], null);

        //设置图像并回收没用的图像资源

        ImageView iv = (ImageView) findViewById(R.id.img2);

        iv.setImageBitmap(bitmap);

        srcBmp.recycle();//图片回收

    }

}

package com.loaderman.customviewdemo;

import android.content.Context;

import android.graphics.Bitmap;

import android.graphics.Canvas;

import android.graphics.Color;

import android.graphics.Paint;

import android.graphics.drawable.BitmapDrawable;

import android.graphics.drawable.StateListDrawable;

import android.util.AttributeSet;

import android.widget.ImageView;

public class StrokeImage extends ImageView {

    public StrokeImage(Context context) {

        super(context);

    }

    public StrokeImage(Context context, AttributeSet attrs) {

        super(context, attrs);

    }

    public StrokeImage(Context context, AttributeSet attrs, int defStyle) {

        super(context, attrs, defStyle);

    }

    @Override

    protected void onFinishInflate() {

        super.onFinishInflate();

        Paint p = new Paint();

        p.setColor(Color.CYAN);

        setStateDrawable(this, p);

    }

    /**

     * 主要函数：为bitmap做光晕效果 * @param v * @param p

     */

    private void setStateDrawable(ImageView v, Paint paint) {

        //拿到源图像

        BitmapDrawable bd = (BitmapDrawable) v.getDrawable();

        Bitmap srcBmp = bd.getBitmap();

        Bitmap bitmap = Bitmap.createBitmap(srcBmp.getWidth(), srcBmp.getHeight(), Bitmap.Config.ARGB_8888);

        Canvas canvas = new Canvas(bitmap);

        canvas.drawBitmap(srcBmp.extractAlpha(), 0, 0, paint);

        //添加state

        StateListDrawable sld = new StateListDrawable();

        sld.addState(new int[]{android.R.attr.state_pressed}, new BitmapDrawable(bitmap));

        //setBackgroundDrawable函数,会移除原有的padding值,如果需要padding,则需调用setPadding

        v.setBackgroundDrawable(sld);

    }

}

<?xml version="1.0" encoding="utf-8"?>

<ScrollView xmlns:android="http://schemas.android.com/apk/res/android"

    android:orientation="vertical"

    android:layout_width="fill_parent"

    android:layout_height="wrap_content">

   <LinearLayout android:orientation="vertical"

       android:layout_width="fill_parent"

       android:layout_height="fill_parent">

      <TextView

          android:layout_width="wrap_content"

          android:layout_height="wrap_content"

          android:textColor="#ff0000"

          android:text="第一个图像点击有惊喜哦"/>

      <com.loaderman.customviewdemo.StrokeImage

          android:layout_width="wrap_content"

          android:layout_height="wrap_content"

          android:src="@drawable/cat"

          android:scaleType="fitCenter"

          android:layout_margin="10dp"

          android:padding="3dp"

          android:clickable="true"/>

      <ImageView

          android:id="@+id/img"

          android:layout_width="wrap_content"

          android:layout_height="wrap_content"

          android:scaleType="fitCenter"

          android:layout_margin="10dp"

          android:clickable="true"/>

      <ImageView

          android:id="@+id/img2"

          android:layout_width="wrap_content"

          android:layout_height="wrap_content"

          android:scaleType="fitCenter"

          android:layout_margin="10dp"

          android:clickable="true"/>

   </LinearLayout>

</ScrollView>

效果图: