Android圓角矩形創建工具RoundRect類

用於把普通圖片轉換為圓角圖像的工具類RoundRect類（復制即可使用）：

import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.graphics.PorterDuff;
import android.graphics.PorterDuffXfermode;
import android.graphics.RectF;
import android.graphics.drawable.BitmapDrawable;
import android.graphics.drawable.Drawable;


public class RoundRect {

    private int width;
    private int height;
    private float cornerRadius;

    /**
     * 用於初始化圓角矩形基本參數
     *
     * @param width        圖片寬度
     * @param height       圖片高度
     * @param cornerRadius 圓角半徑
     */
    public RoundRect(int width, int height, float cornerRadius) {
        this.width = width;
        this.height = height;
        this.cornerRadius = cornerRadius;
    }

    /**
     * 用於把普通圖片轉換為圓角矩形圖像
     *
     * @param path 圖片路徑
     * @return output 轉換后的圓角矩形圖像
     */
    Bitmap toRoundRect(String path) {
        //創建位圖對象
        Bitmap photo = lessenUriImage(path);
        return Transformation(photo);
    }

    /**
     * 用於把普通圖片轉換為圓角矩形圖像
     *
     * @param imageID 圖片資源ID
     * @param context 上下文對象
     * @return output 轉換后的圓角矩形圖像
     */
    Bitmap toRoundRect(Context context, int imageID) {
        //創建位圖對象
        Bitmap photo = BitmapFactory.decodeResource(context.getResources(), imageID);
        return Transformation(photo);
    }

    /**
     * 用於把Uri圖片轉換為Bitmap對象
     *
     * @param path 圖片URI地址
     * @return 生成的Bitmap對象
     */
    public final static Bitmap lessenUriImage(String path) {
        BitmapFactory.Options options = new BitmapFactory.Options();
        options.inJustDecodeBounds = true;
        Bitmap bitmap = BitmapFactory.decodeFile(path, options); //此時返回 bm 為空
        options.inJustDecodeBounds = false; //縮放比。由於是固定比例縮放，只用高或者寬其中一個數據進行計算即可
        int be = (int) (options.outHeight / (float) 320);
        if (be <= 0) be = 1;
        options.inSampleSize = be; //重新讀入圖片，注意此時已經把 options.inJustDecodeBounds 設回 false 了
        bitmap = BitmapFactory.decodeFile(path, options);
        int w = bitmap.getWidth();
        int h = bitmap.getHeight();
        System.out.println(w + " " + h); //after zoom
        return bitmap;
    }

    /**
     * 用於把Bitmap圖像轉換為圓角圖像
     *
     * @param photo 需要轉換的Bitmap對象
     * @return 轉換成圓角的Bitmap對象
     */
    private Bitmap Transformation(Bitmap photo) {

        //根據源文件新建一個darwable對象
        Drawable imageDrawable = new BitmapDrawable(photo);

        // 新建一個新的輸出圖片
        Bitmap output = Bitmap.createBitmap(width, height, Bitmap.Config.ARGB_8888);
        Canvas canvas = new Canvas(output);

        // 新建一個矩形
        RectF outerRect = new RectF(0, 0, width, height);

        // 產生一個紅色的圓角矩形
        Paint paint = new Paint(Paint.ANTI_ALIAS_FLAG);
        paint.setColor(Color.RED);
        canvas.drawRoundRect(outerRect, cornerRadius, cornerRadius, paint);

        // 將源圖片繪制到這個圓角矩形上
        paint.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.SRC_IN));
        imageDrawable.setBounds(0, 0, width, height);
        canvas.saveLayer(outerRect, paint, Canvas.ALL_SAVE_FLAG);
        imageDrawable.draw(canvas);
        canvas.restore();

        return output;
    }

}

測試效果：

創建矩形圖標：

public class MainActivity extends Activity {
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.image);

        ImageView image = (ImageView)findViewById(R.id.image);
        RoundRect roundRect = new RoundRect(500,500,100);
        Bitmap photo = roundRect.toRoundRect(this,R.drawable.kms);
        image.setImageBitmap(photo);
    }
}

創建圓形頭像：

public class MainActivity extends Activity {
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.image);

        ImageView image = (ImageView)findViewById(R.id.image);
        RoundRect roundRect = new RoundRect(500,500,300);
        Bitmap photo = roundRect.toRoundRect(this,R.drawable.indark);
        image.setImageBitmap(photo);
    }
}