Android画图之抗锯齿

2021-07-15 02:43:36

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。

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。

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