说明：  This function saves a figure or single axes to one or more vector and/or bitmap file formats, and/or outputs a rasterized version to the workspace, with the following properties: - Figure/axes reproduced as it appears on screen - Cropped borders (optional) - Embedded fonts (pdf only) - Improved line and grid line styles - Anti-aliased graphics (bitmap formats) - Render images at native resolution (optional for bitmap formats) - Transparent background supported (pdf, eps, png) - Semi-transparent patch objects supported (png only)