Bitmap 与Drawable相互转换

Drawable 转 Bitmap

import android.graphics.Bitmap;
import android.graphics.drawable.Drawable;
import android.graphics.drawable.BitmapDrawable;

Drawable d = getResource().getDrawable(R.id.background);

BitmapDrawable bd = (BitmapDrawable) d;

Bitmap bp = bd.getBitmap();

Bitmap 转 Drawable

Bitmap bm=XXX;

Drawable bd=(Drawable)(new BitmapDrawable(bm));
//因为BtimapDrawable是Drawable的子类，最终直接使用bd对象即可。

Drawable 缩放：

static Bitmap zoomDrawable(Drawable drawable, int w, int h)
    {
              int width = drawable.getIntrinsicWidth();
              int height= drawable.getIntrinsicHeight();
              Bitmap oldbmp = ((BitmapDrawable)drawable).getBitmap();
              Matrix matrix = new Matrix();   // 创建操作图片用的Matrix对象
              float scaleWidth = ((float)w / width);   // 计算缩放比例
              float scaleHeight = ((float)h / height);
              matrix.postScale(scaleWidth, scaleHeight);         // 设置缩放比例
              Bitmap newbmp = Bitmap.createBitmap(oldbmp, 0, 0, width, height, matrix, true);       // 建立新的bitmap，其内容是对原bitmap的缩放后的图
              return newbmp;       // 把bitmap转换成drawable并返回
    }