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 boundsmOldBounds.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;}