Android画图之抗锯齿

在画图的时候，图片如果旋转或缩放之后，总是会出现那些华丽的锯齿。其实Android自带了解决方式。
    方法一：给Paint加上抗锯齿标志。然后将Paint对象作为参数传给canvas的绘制方法。

 paint.setAntiAlias(true);

 

    方法二：给Canvas加上抗锯齿标志。
有些地方不能用paint的，就直接给canvas加抗锯齿，更方便。

 canvas.setDrawFilter(new PaintFlagsDrawFilter(0, Paint.ANTI_ALIAS_FLAG|Paint.FILTER_BITMAP_FLAG));

 

      测试代码如下： 

 import android.content.Context;
 import android.graphics.Bitmap;
 import android.graphics.BitmapFactory;
 import android.graphics.Canvas;
 import android.graphics.Matrix;
 import android.graphics.Paint;
 import android.graphics.PaintFlagsDrawFilter;
 import android.view.View;

 public class MyView extends View {
     private PaintFlagsDrawFilter pfd;
     private Paint mPaint = new Paint();
     private Matrix matrix = new Matrix();;
     private Bitmap bmp;

     public MyView(Context context) {
         super(context);
         initialize();
     }

     private void initialize() {
         pfd = new PaintFlagsDrawFilter(0, Paint.ANTI_ALIAS_FLAG|Paint.FILTER_BITMAP_FLAG);
         mPaint.setAntiAlias(true);
         matrix.setRotate(30);
         matrix.postScale(0.5f, 0.5f);
         bmp = BitmapFactory.decodeResource(getResources(), R.drawable.show);
     }

     @Override
     public void dispatchDraw(Canvas canvas) {
         canvas.translate(100, 0);
         canvas.drawBitmap(bmp, matrix, null);
         canvas.translate(0, 250);
         canvas.drawBitmap(bmp, matrix, mPaint);
         canvas.setDrawFilter(pfd);
         canvas.translate(0, 250);
         canvas.drawBitmap(bmp, matrix, null);
     }
 }

 

    下图是效果：

 

      可以看出，两种方式都挺有效的。