Android ImageView上的抗锯齿圆角

Question

我是android dev的新手,现在我已经尝试了几个小时为ImageView添加漂亮而光滑的圆角,但没有成功.

我尝试的第一件事就是直接对我的图像进行圆角处理,但这意味着要更改位图,因为我需要保留原始位图,而且这些都非常大,这对内存不友好.这也会导致其他困难,因为我的ImageView是流动的.

我尝试使用的第二件事是继承我的视图后的clipPath方法.这有效,但角落是别名.然后我尝试添加一个PaintFlagsDrawFilter来实现别名,但这没有用.我正在使用monodroid,我想知道这应该用于Java.

这是我的代码(C#):

public class MyImageView : ImageView
{
    private float[] roundedCorner;

    /**
     * Contains the rounded  corners for the view.
     * You can define one, four or height values.
     * This behaves as the css border-radius property
     * 
     * @see http://developer.android.com/reference/android/graphics/Path.html#addRoundRect(android.graphics.RectF, float[], android.graphics.Path.Direction)
     */
    public float[] RoundedCorners{
        get{
            return roundedCorner;
        }
        set{
            float[] finalValue = new float[8];
            int i=0;
            if(value.Length == 1){
                for(i=0; i<8;i++){
                    finalValue[i] = value[0];
                }
            }else if(value.Length == 4){
                for(i=0; i<4;i++){
                    finalValue[2*i] = value[i];
                    finalValue[2*i+1] = value[i];
                }
            }

            roundedCorner = finalValue;
        }
    }

    public SquareImageView (Context context) :
        base (context)
    {
        Initialize ();
    }

    public SquareImageView (Context context, IAttributeSet attrs) :
        base (context, attrs)
    {
        Initialize ();
    }

    private void Initialize ()
    {
        RoundedCorners = new float[]{0,0,0,0};
    }

    public override void Draw (Android.Graphics.Canvas canvas)
    {
        Path path = new Path();
        path.AddRoundRect(new RectF(0,0, Width,Height),RoundedCorners, Path.Direction.Cw);

        canvas.ClipPath(path);

        base.Draw (canvas);
    }

    /**
     *  try to add antialiasing.
             */
    protected override void DispatchDraw (Canvas canvas)
    {

        canvas.DrawFilter = new PaintFlagsDrawFilter((PaintFlags)1, PaintFlags.AntiAlias);
        base.DispatchDraw (canvas);
    }

}

谢谢你的帮助!

Answer 1

使用下面的代码

public Bitmap getRoundedCornerBitmap(Bitmap bitmap, int pixels) 
    {
        Bitmap output = null;

        if(bitmap != null)
        {
            output = Bitmap.createBitmap(bitmap.getWidth(), bitmap.getHeight(), Config.ARGB_8888);
            Canvas canvas = new Canvas(output);

            final int color = 0xff424242;
            final Paint paint = new Paint();
            final Rect rect = new Rect(0, 0, bitmap.getWidth(), bitmap.getHeight());
            final RectF rectF = new RectF(rect);
            final float roundPx = pixels;

            paint.setAntiAlias(true);
            canvas.drawARGB(0, 0, 0, 0);
            paint.setColor(color);
            canvas.drawRoundRect(rectF, roundPx, roundPx, paint);

            paint.setXfermode(new PorterDuffXfermode(Mode.SRC_IN));
            canvas.drawBitmap(bitmap, rect, rect, paint);
        }

        return output;
    }

并像这样调用这个方法

   imageView.setImageBitmap(getRoundedCornerBitmap(bitmap, 10));