读取sd卡下图片，由图片路径转换为bitmap

public Bitmap convertToBitmap(String path, int w, int h) {
			BitmapFactory.Options opts = new BitmapFactory.Options();
			// 设置为ture只获取图片大小
			opts.inJustDecodeBounds = true;
			opts.inPreferredConfig = Bitmap.Config.ARGB_8888;
			// 返回为空
			BitmapFactory.decodeFile(path, opts);
			int width = opts.outWidth;
			int height = opts.outHeight;
			float scaleWidth = 0.f, scaleHeight = 0.f;
			if (width > w || height > h) {
				// 缩放
				scaleWidth = ((float) width) / w;
				scaleHeight = ((float) height) / h;
			}
			opts.inJustDecodeBounds = false;
			float scale = Math.max(scaleWidth, scaleHeight);
			opts.inSampleSize = (int)scale;
			WeakReference<Bitmap> weak = new WeakReference<Bitmap>(BitmapFactory.decodeFile(path, opts));
			return Bitmap.createScaledBitmap(weak.get(), w, h, true);
		}

其中w和h你需要转换的大小

path转换为bitmap:上面方法即可；

imageview获取drawable并转换为 bitmap ：Bitmap bt= ((BitmapDrawable) mImageview.getDrawable()).getBitmap();

resourceid转换为bitmap：Bitmap bt = BitmapFactory.decodeResource(getResources(), R.drawable.resourceid);

Drawable转换为bitmap：Bitmap bt= ((BitmapDrawable) Drawable).getBitmap();

因为BitmapDrawable是继承Drawable，所以可以灵活的转换