Drawble高效创建缩略图方法

代码是从android源码代中抽出来的，感觉不错。。。如果大家有什么建议，一起交流，谢谢！！！

public Drawable createIconThumbnail(Drawable icon,int MIconWidth,int mIconHeight) {
		int width = mIconWidth;
		int height = mIconHeight;

		final int iconWidth = icon.getIntrinsicWidth();
		final int iconHeight = icon.getIntrinsicHeight();

		if (icon instanceof PaintDrawable) {
			PaintDrawable painter = (PaintDrawable) icon;
			painter.setIntrinsicWidth(width);
			painter.setIntrinsicHeight(height);
		}

		if (width > 0 && height > 0) {
			if (width < iconWidth || height < iconHeight) {
				final float ratio = (float) iconWidth / iconHeight;

				if (iconWidth > iconHeight) {
					height = (int) (width / ratio);
				} else if (iconHeight > iconWidth) {
					width = (int) (height * ratio);
				}

				final Bitmap.Config c = icon.getOpacity() != PixelFormat.OPAQUE ? Bitmap.Config.ARGB_8888
						: Bitmap.Config.RGB_565;
				final Bitmap thumb = Bitmap.createBitmap(mIconWidth,
						mIconHeight, c);
				final Canvas canvas = mCanvas;
				canvas.setBitmap(thumb);
				// Copy the old bounds to restore them later
				// If we were to do oldBounds = icon.getBounds(),
				// the call to setBounds() that follows would
				// change the same instance and we would lose the
				// old bounds
				mOldBounds.set(icon.getBounds());
				final int x = (mIconWidth - width) / 2;
				final int y = (mIconHeight - height) / 2;
				icon.setBounds(x, y, x + width, y + height);
				icon.draw(canvas);
				icon.setBounds(mOldBounds);
				icon = new BitmapDrawable(getResources(), thumb);
			} else if (iconWidth < width && iconHeight < height) {
				final Bitmap.Config c = Bitmap.Config.ARGB_8888;
				final Bitmap thumb = Bitmap.createBitmap(mIconWidth,
						mIconHeight, c);
				final Canvas canvas = mCanvas;
				canvas.setBitmap(thumb);
				mOldBounds.set(icon.getBounds());
				final int x = (width - iconWidth) / 2;
				final int y = (height - iconHeight) / 2;
				icon.setBounds(x, y, x + iconWidth, y + iconHeight);
				icon.draw(canvas);
				icon.setBounds(mOldBounds);
				icon = new BitmapDrawable(getResources(), thumb);
			}
		}

		return icon;
	}