Android画图之抗锯齿

此转

    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。