- (UIImage *)stretchableImageWithLeftCapWidth:(NSInteger)leftCapWidth topCapHeight:(NSInteger)topCapHeight;

   UIImage *image = [UIImage imageNamed:@"圓角矩形-7-拷貝"];
    //原始圖片樣式添加
    self.originalImageView.image = image;
    //沒處理好的圖片
    self.badImageView.image = image;
//圖片處理后的 將被棄用 方法一：
//這個(gè)函數(shù)是UIImage的一個(gè)實(shí)例函數(shù)，它的功能是創(chuàng)建一個(gè)內(nèi)容可拉伸，而邊角不拉伸的圖片，需要兩個(gè)參數(shù)，第一個(gè)是左邊不拉伸區(qū)域的寬度，第二個(gè)參數(shù)是上面不拉伸的高度。
//根據(jù)設(shè)置的寬度和高度，將接下來的一個(gè)像素進(jìn)行左右擴(kuò)展和上下拉伸。
    [self.textImageView setImage:[image stretchableImageWithLeftCapWidth:image.size.width*0.5 topCapHeight:image.size.height*0.5]];
//注意：可拉伸的范圍都是距離leftCapWidth后的1豎排像素，和距離topCapHeight后的1橫排像素。

- (UIImage *)resizableImageWithCapInsets:(UIEdgeInsets)capInsets; 
// create a resizable version of this image. the interior is tiled when drawn.

   UIImage *image = [UIImage imageNamed:@"圓角矩形-7-拷貝"];
    //原始圖片樣式添加
    self.originalImageView.image = image;
    //沒處理好的圖片
    self.badImageView.image = image;
//處理圖片 iOS 5 方法三：
            CGFloat width = image.size.width;
            CGFloat height = image.size.height;
            CGFloat top = height/2.0f - 0.5f; // 頂端蓋高度
            CGFloat bottom = height/2.0f - 0.5f ; // 底端蓋高度
            CGFloat left = width/2.0f - 0.5f; // 左端蓋寬度
            CGFloat right = width/2.0f - 0.5f; // 右端蓋寬度
            UIEdgeInsets insets = UIEdgeInsetsMake(top, left, bottom, right);
            //創(chuàng)建 一個(gè)可變的image版本，內(nèi)部平鋪，類：UIImageResizingModeTile模式；
            self.textImageView.image = [image resizableImageWithCapInsets:insets];

- (UIImage *)resizableImageWithCapInsets:(UIEdgeInsets)capInsets resizingMode:(UIImageResizingMode)resizingMode;
 // the interior is resized according to the resizingMode

   UIImage *image = [UIImage imageNamed:@"圓角矩形-7-拷貝"];
    //原始圖片樣式添加
    self.originalImageView.image = image;
    //沒處理好的圖片
    self.badImageView.image = image;
            //處理圖片 iOS 6 方法二：
            CGFloat width = image.size.width;
            CGFloat height = image.size.height;
            CGFloat top = height/2.0f - 0.5f; // 頂端蓋高度
            CGFloat bottom = height/2.0f - 0.5f ; // 底端蓋高度
            CGFloat left = width/2.0f - 0.5f; // 左端蓋寬度
            CGFloat right = width/2.0f - 0.5f; // 右端蓋寬度
            UIEdgeInsets insets = UIEdgeInsetsMake(top, left, bottom, right);
            // 指定為拉伸模式，伸縮后重新賦值
            //UIImageResizingModeStretch：拉伸模式，通過拉伸UIEdgeInsets指定的矩形區(qū)域來填充圖片
            //UIImageResizingModeTile：平鋪模式，通過重復(fù)顯示UIEdgeInsets指定的矩形區(qū)域來填充圖片
            _textImageView.image = [image resizableImageWithCapInsets:insets resizingMode:UIImageResizingModeTile];
// Swift
let image = UIImage(named: "rounded_rectangle_7_copy")
if image != nil {  
    self.originalImageView.image = image  
    self.badImageView.image = image  
} else {  
    self.originalImageView.image = image  
    self.badImageView.image = image  
}
let width = image?.size.width ?? 0  
let height = image?.size.height ?? 0
let top = height / 2 - 0.5  
let bottom = height / 2 - 0.5  
let left = width / 2 - 0.5  
let right = width / 2 - 0.5
let insets = UIEdgeInsets(top: top, left: left, bottom: bottom, right: right)
if image != nil {  
    let resizingMode = UIImage.resizableImageResizingMode.tile  
    self.textImageView.image = UIImage(resizableImageWithCapInsets: insets, resizingMode: resizingMode)  
} else {  
    self.textImageView.image = UIImage(resizableImageWithCapInsets: insets, resizingMode: resizingMode)  
}

typedef NS_ENUM(NSInteger, UIViewContentMode) {
    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,
};

//使用方法
[ImageView setContentMode:UIViewContentModeScaleAspectFit];
//OR
ImageView.contentMode = UIViewContentModeScaleAspectFit;
//以下方法，圖片保持原有大小比例的情況下，展示在ImageView的上下左右等位置；如果視圖大小小于圖片的尺寸，則圖片會(huì)超出視圖邊界；
    UIViewContentModeTop,
    UIViewContentModeBottom,
    UIViewContentModeLeft,
    UIViewContentModeRight,
    UIViewContentModeTopLeft,
    UIViewContentModeTopRight,
    UIViewContentModeBottomLeft,
    UIViewContentModeBottomRight,
    UIViewContentModeCenter,  
    UIViewContentModeScaleToFill,  //根據(jù)視圖的比例去拉伸圖片內(nèi)容。圖片可能變形；
    UIViewContentModeScaleAspectFit,  //保持圖片內(nèi)容的縱橫比例，來適應(yīng)視圖的大小。
    UIViewContentModeScaleAspectFill,   //用圖片內(nèi)容來填充視圖的大小，多余得部分可以被修剪掉來填充整個(gè)視圖邊界。 
    UIViewContentModeRedraw,     //這個(gè)選項(xiàng)是單視圖的尺寸位置發(fā)生變化的時(shí)候通過調(diào)用setNeedsDisplay方法來重新顯示。