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：