UIViewContentMode各类型效果

typedef enum {     UIViewContentModeScaleToFill,     UIViewContentModeScaleAspectFit,      // contents scaled to fit with fixed aspect. remainder is transparent     UIViewContentModeScaleAspectFill,     // contents scaled to fill with fixed aspect. some portion of content may be clipped.     UIViewContentModeRedraw,              // redraw on bounds change (calls -setNeedsDisplay)     UIViewContentModeCenter,              // contents remain same size. positioned adjusted.     UIViewContentModeTop,     UIViewContentModeBottom,     UIViewContentModeLeft,     UIViewContentModeRight,     UIViewContentModeTopLeft,     UIViewContentModeTopRight,     UIViewContentModeBottomLeft,     UIViewContentModeBottomRight, } UIViewContentMode;