Android画图之抗锯齿paint和Canvas两种方式实例

Z时代
2024-01-10
分类：综合

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));

eg：


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); 
  } 
}