iOS图片拉伸

UIImage * img = [UIImage imageNamed:@"3X"];
float w = img.size.width;
float h = img.size.height;

//图片拉伸 当imgview的frame跟img不一样大时就会拉伸图片来填充
//第一个参数 UIEdgeInsets 是规定上下左右到img边的部分不拉伸受到保护 中间部分进行拉伸

//UIImageResizingModeStretch 拉伸
//UIImageResizingModeTile 平铺
UIImage * newImg = [img resizableImageWithCapInsets:
UIEdgeInsetsMake(h * 0.5, w * 0.5, h * 0.5, w * 0.5)         
resizingMode:
UIImageResizingModeStretch];