Android畫圖之抗鋸齒－自由手記

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原文位址：Android畫圖之抗鋸齒作者：OiSoft

在畫圖的時候，圖片如果旋轉或縮放之後，總是會出現那些華麗的鋸齒。其實Android自帶瞭解決方式。

方法一：給Paint加上抗鋸齒標誌。然後將Paint物件作為參數傳給canvas的繪製方法。

paint.setAntiAlias(true);

方法二：給Canvas加上抗鋸齒標誌。

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);
    }
}

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);
}
}