android 画图用到的DrawFilter

android 画图用到的DrawFilter

public class
DrawFilter
extends Object

Google官方的解释是这样的
A DrawFilter subclass can be installed in a Canvas. When it is present, it can modify the paint that is used to draw (temporarily). With this, a filter can disable/enable antialiasing, or change the color for everything this is drawn.
DrawFilter子类可以安装在画布上。当它存在,它可以修改所使用的画笔(暂时)。当它存在时一个过滤器可以禁用/启用抗锯齿,或改变画的颜色的颜色。

当我们绘制斜线、或者旋转图片的时候就会出现锯齿效果，消除锯齿效果，一般要设置画笔和画布的抗锯齿效果。
就如文档中说的使用DrawFilter一般会使用它的子类PaintFlagsDrawFilter(int clearBits, int setBits) 。参数是要设置画笔的clearBits 旗帜和设置setBits旗帜。
*

mWavePaint.setAntiAlias(true); //设置画笔抗锯齿 mDrawFilter = new PaintFlagsDrawFilter(0, Paint.ANTI_ALIAS_FLAG | Paint.FILTER_BITMAP_FLAG);  canvas.setDrawFilter(mDrawFilter);  // 从canvas层面去除绘制时锯齿

• 具体例子

package com.bm;import android.content.Context;import android.graphics.Bitmap;import android.graphics.BitmapFactory;import android.graphics.Canvas;import android.graphics.Color;import android.graphics.DrawFilter;import android.graphics.Matrix;import android.graphics.Paint;import android.graphics.PaintFlagsDrawFilter;import android.view.View;public class DrawFilterView extends View {  private Paint mPaintFilter;  private DrawFilter mDrawFilter;     private Bitmap bitmap;  public DrawFilterView(Context context) {    super(context);    initView();  }  private void initView(){    mPaintFilter = new Paint();    mPaintFilter.setColor(Color.WHITE);    mDrawFilter=new PaintFlagsDrawFilter(0, Paint.ANTI_ALIAS_FLAG | Paint.FILTER_BITMAP_FLAG);      //设置图片的抗锯齿效果    bitmap=BitmapFactory.decodeResource(this.getResources(), R.drawable.icon);//获取src图片  }  @Override  protected void onDraw(Canvas canvas) {    super.onDraw(canvas);    canvas.drawLine(0, 0, 100, 80, mPaintFilter);//不抗锯齿的画笔画斜线    mPaintFilter.setAntiAlias(true);    canvas.drawLine(0, 0, 100, 150, mPaintFilter);//抗锯齿的画笔画斜线    //不抗锯齿画原图    canvas.drawBitmap(bitmap, 0, 0, mPaintFilter);    //不抗锯齿画旋转图    Matrix maMiX = new Matrix();//矩阵    maMiX.setRotate(75);//旋转75度      maMiX.postTranslate(100, 100);//平移    canvas.drawBitmap(bitmap, maMiX, mPaintFilter);    //抗锯齿画旋转图    canvas.setDrawFilter(mDrawFilter); //设置图形、图片的抗锯齿。    Matrix maMiY = new Matrix();    maMiY.setRotate(75);    maMiY.postTranslate(200, 200);    canvas.drawBitmap(bitmap, maMiY, mPaintFilter);  }}