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: