Android将本地资源图片转换成Drawable,进行设置大小操作

/**
 * 将Drawable转换为Bitmap
 * @param drawable
 * @return
 */
private Bitmap drawableToBitmap(Drawable drawable) {
  //取drawable的宽高
  int width = drawable.getIntrinsicWidth();
  int height = drawable.getIntrinsicHeight();
  //取drawable的颜色格式
  Bitmap.Config cOnfig= drawable.getOpacity() != PixelFormat.OPAQUE 
        &＃63; Bitmap.Config.ARGB_8888
        : Bitmap.Config.RGB_565;
  //创建对应的bitmap
  Bitmap bitmap = Bitmap.createBitmap(width, height, config);
  //创建对应的bitmap的画布
  Canvas canvas = new Canvas(bitmap);
  drawable.setBounds(0, 0, width, height);
  //把drawable内容画到画布中
  drawable.draw(canvas);
  return bitmap;
}

/**
 * 将本地资源图片大小缩放
 * @param resId
 * @param w
 * @param h
 * @return
 */
 public Drawable zoomImage(int resId, int w, int h){
  Resources res = mContext.getResources();
  Bitmap oldBmp = BitmapFactory.decodeResource(res, resId);
  Bitmap newBmp = Bitmap.createScaledBitmap(oldBmp,w, h, true);
  Drawable drawable = new BitmapDrawable(res, newBmp);
  return drawable;
}

/**
 * 缩放Drawable
 *@drawable 原来的Drawable
 *@w 指定的宽
 *@h 指定的高
 */
public Drawable zoomDrawable(Drawable drawable, int w, int h){
  //获取原来Drawable的宽高
  int width = drawable.getIntrinsicWidth();
  int height = drawable.getIntrinsicHeight();
  //将Drawable转换成Bitmap
  Bitmap oldbmp = drawableToBitmap(drawable);
  //计算scale
  Matrix matrix = new Matrix();
  float scaleWidth = ((float)w/width);
  float scaleHeight = ((float)h/height);
  matrix.postScale(scaleWidth, scaleHeight);
  //生成新的Bitmap
  Bitmap newbmp = Bitmap.createBitmap(oldbmp, 0, 0, width, height, matrix, true);
  //设置bitmap转成drawable后尺寸不变 
  //这个很关键后面解释！！
  DisplayMetrics metrics = new DisplayMetrics();
  manager.getDefaultDisplay().getMetrics(metrics);
  Resources resources = new Resources(mContext.getAssets(), metrics, null);
  return new BitmapDrawable(resources, newbmp);
}

DisplayMetrics metrics = new DisplayMetrics();
manager.getDefaultDisplay().getMetrics(metrics);
Resources resources = new Resources(mContext.getAssets(), metrics, null);