Android Paint之MaskFilter详解

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这一篇来简单分析一下Paint的setMaskFilter(MaskFilter maskfilter)方法，其中MaskFilter有两个子类，一个BlurMaskFilter一个是EmbossMaskFilter，这里先来看一下BlurMaskFilter这个类的源码

    public enum Blur {        /**         * Blur inside and outside the original border.         */        NORMAL(0),        /**         * Draw solid inside the border, blur outside.         */        SOLID(1),        /**         * Draw nothing inside the border, blur outside.         */        OUTER(2),        /**         * Blur inside the border, draw nothing outside.         */        INNER(3);                Blur(int value) {            native_int = value;        }        final int native_int;    }        /**     * Create a blur maskfilter.     *     * @param radius The radius to extend the blur from the original mask. Must be > 0.     * @param style  The Blur to use     * @return       The new blur maskfilter     */    public BlurMaskFilter(float radius, Blur style) {        native_instance = nativeConstructor(radius, style.native_int);    }

构造方法很简单，传入一个半径，是绘制阴影模糊的半径，其中类型有以上4种，这里就不在一一叙述，先看一下代码然后在直接看运行结果

public class MaskFilterView extends View {private Paint paint;private TextPaint mTextPaint;private BlurMaskFilter bmf1;private BlurMaskFilter bmf2;private BlurMaskFilter bmf3;private BlurMaskFilter bmf4;public MaskFilterView(Context context, AttributeSet attrs) {super(context, attrs);paint = new Paint(Paint.ANTI_ALIAS_FLAG);paint.setColor(Color.RED);paint.setStyle(Style.FILL_AND_STROKE);mTextPaint = new TextPaint(Paint.ANTI_ALIAS_FLAG);mTextPaint.setTextSize(64);mTextPaint.setColor(Color.BLUE);mTextPaint.setTextAlign(Align.CENTER);bmf1 = new BlurMaskFilter(100, Blur.NORMAL);bmf2 = new BlurMaskFilter(100, Blur.SOLID);bmf3 = new BlurMaskFilter(100, Blur.OUTER);bmf4 = new BlurMaskFilter(100, Blur.INNER);}@Overrideprotected void onDraw(Canvas canvas) {super.onDraw(canvas);canvas.translate(0, 200);canvas.drawColor(Color.WHITE);paint.setMaskFilter(bmf1);canvas.drawCircle(300, 300, 150, paint);canvas.drawText("NORMAL", 300, 600, mTextPaint);paint.setMaskFilter(bmf2);canvas.drawCircle(300, 900, 150, paint);canvas.drawText("SOLID", 300, 1200, mTextPaint);paint.setMaskFilter(bmf3);canvas.drawCircle(800, 300, 150, paint);canvas.drawText("OUTER", 800, 600, mTextPaint);paint.setMaskFilter(bmf4);canvas.drawCircle(800, 900, 150, paint);canvas.drawText("INNER", 800, 1200, mTextPaint);}}

在Androidmanifest中要加上下面这段代码，否则不会出现任何模糊效果

        android:hardwareAccelerated="false"

来看一下运行的结果

效果很明显，这里就不在详述。下面再来看一下EmbossMaskFilter这个类，先看一下他的构造方法

    /**     * Create an emboss maskfilter     *     * @param direction  array of 3 scalars [x, y, z] specifying the direction of the light source     * @param ambient    0...1 amount of ambient light     * @param specular   coefficient for specular highlights (e.g. 8)     * @param blurRadius amount to blur before applying lighting (e.g. 3)     * @return           the emboss maskfilter     */    public EmbossMaskFilter(float[] direction, float ambient, float specular, float blurRadius) {        if (direction.length < 3) {            throw new ArrayIndexOutOfBoundsException();        }        native_instance = nativeConstructor(direction, ambient, specular, blurRadius);    }

其中direction表示x,y,z的三个方向，ambient表示的是光的强度，范围为[0-1]，specular是反射亮度的系数，blurRadius是指模糊的半径，看一下代码

package test.view;import android.annotation.SuppressLint;import android.content.Context;import android.graphics.Canvas;import android.graphics.Color;import android.graphics.EmbossMaskFilter;import android.graphics.Paint;import android.graphics.Paint.Style;import android.util.AttributeSet;import android.view.View;public class MaskFilterView extends View {private Paint paint;EmbossMaskFilter emboss;public MaskFilterView(Context context, AttributeSet attrs) {super(context, attrs);paint = new Paint(Paint.ANTI_ALIAS_FLAG);paint.setColor(Color.RED);paint.setStyle(Style.STROKE);paint.setStrokeWidth(32);paint.setTextSize(368);float[] direction = new float[] { 1, 1, 1 };// 设置环境光亮度float light = 0.1f;// 选择要应用的反射等级float specular = 8;// 向mask应用一定级别的模糊float blur = 3;emboss = new EmbossMaskFilter(direction, light, specular, blur);}@Overrideprotected void onDraw(Canvas canvas) {super.onDraw(canvas);canvas.drawText("山大王", 30, 400, paint);}@SuppressLint("NewApi")public void setparam(float x, float y, float z, float light,float specular, float blur) {emboss = new EmbossMaskFilter(new float[] { x, y, z }, light, specular,blur);paint.setMaskFilter(emboss);invalidate();}}

看一下运行结果，这个会根据不同的值产生不同的结果，下面只截取已其中的一个