[Python] save a figure in matplotlib with figure border removed

def SaveFigureAsImage(fileName,fig=None,**kwargs):
    ''' Save a Matplotlib figure as an image without borders or frames.
       Args:
            fileName (str): String that ends in .png etc.

            fig (Matplotlib figure instance): figure you want to save as the image
        Keyword Args:
            orig_size (tuple): width, height of the original image used to maintain
            aspect ratio.
    '''
    fig_size = fig.get_size_inches()
    w,h = fig_size[0], fig_size[1]
    fig.patch.set_alpha(0)
    if kwargs.has_key('orig_size'): # Aspect ratio scaling if required
        w,h = kwargs['orig_size']
        w2,h2 = fig_size[0],fig_size[1]
        fig.set_size_inches([(w2/w)*w,(w2/w)*h])
        fig.set_dpi((w2/w)*fig.get_dpi())
    a=fig.gca()
    a.set_frame_on(False)
    a.set_xticks([]); a.set_yticks([])
    plt.axis('off')
    plt.xlim(0,w); plt.ylim(h,0)
    fig.savefig(fileName, transparent=True, bbox_inches='tight', \
                        pad_inches=0)