Android开发之圆角矩形创建工具RoundRect类定义与用法分析

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;
  /**
   * 用于初始化圆角矩形基本参数
   *
   * @param width    图片宽度
   * @param height    图片高度
   * @param cornerRadius 圆角半径
   */
  public RoundRect(int width,int height,float cornerRadius) {
    this.width = width;
    this.height = height;
    this.cornerRadius = cornerRadius;
  }
  /**
   * 用于把普通图片转换为圆角矩形图像
   *
   * @param path 图片路径
   * @return output 转换后的圆角矩形图像
   */
  Bitmap toRoundRect(String path) {
    //创建位图对象
    Bitmap photo = lessenUriImage(path);
    return Transformation(photo);
  }
  /**
   * 用于把普通图片转换为圆角矩形图像
   *
   * @param imageID 图片资源ID
   * @param context 上下文对象
   * @return output 转换后的圆角矩形图像
   */
  Bitmap toRoundRect(Context context,int imageID) {
    //创建位图对象
    Bitmap photo = BitmapFactory.decodeResource(context.getResources(),imageID);
    return Transformation(photo);
  }
  /**
   * 用于把Uri图片转换为Bitmap对象
   *
   * @param path 图片URI地址
   * @return 生成的Bitmap对象
   */
  public final static Bitmap lessenUriImage(String path) {
    BitmapFactory.Options options = new BitmapFactory.Options();
    options.inJustDecodeBounds = true;
    Bitmap bitmap = BitmapFactory.decodeFile(path,options); //此时返回 bm 为空
    options.inJustDecodeBounds = false; //缩放比。由于是固定比例缩放，只用高或者宽其中一个数据进行计算即可
    int be = (int) (options.outHeight / (float) 320);
    if (be <= 0) be = 1;
    options.inSampleSize = be; //重新读入图片，注意此时已经把 options.inJustDecodeBounds 设回 false 了
    bitmap = BitmapFactory.decodeFile(path,options);
    int w = bitmap.getWidth();
    int h = bitmap.getHeight();
    System.out.println(w + " " + h); //after zoom
    return bitmap;
  }
  /**
   * 用于把Bitmap图像转换为圆角图像
   *
   * @param photo 需要转换的Bitmap对象
   * @return 转换成圆角的Bitmap对象
   */
  private Bitmap Transformation(Bitmap photo) {
    //根据源文件新建一个darwable对象
    Drawable imageDrawable = new BitmapDrawable(photo);
    // 新建一个新的输出图片
    Bitmap output = Bitmap.createBitmap(width,height,Bitmap.Config.ARGB_8888);
    Canvas canvas = new Canvas(output);
    // 新建一个矩形
    RectF outerRect = new RectF(0,width,height);
    // 产生一个红色的圆角矩形
    Paint paint = new Paint(Paint.ANTI_ALIAS_FLAG);
    paint.setColor(Color.RED);
    canvas.drawRoundRect(outerRect,cornerRadius,paint);
    // 将源图片绘制到这个圆角矩形上
    paint.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.SRC_IN));
    imageDrawable.setBounds(0,height);
    canvas.saveLayer(outerRect,paint,Canvas.ALL_SAVE_FLAG);
    imageDrawable.draw(canvas);
    canvas.restore();
    return output;
  }
}

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);
  }
}

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(500,300);
    Bitmap photo = roundRect.toRoundRect(this,R.drawable.indark);
    image.setImageBitmap(photo);
  }
}