1. UIImageView整體拉伸

UIImageView-contentMode

typedef NS_ENUM(NSInteger, UIViewContentMode) {
UIViewContentModeScaleToFill, // 默認(rèn) 拉伸（會(huì)變形）
UIViewContentModeScaleAspectFit, // 等比例拉伸
UIViewContentModeScaleAspectFill, // 等比例填充
UIViewContentModeRedraw, // redraw on bounds change (這個(gè)不清楚)
UIViewContentModeCenter, // 下面的就是不拉伸按位置顯示了
UIViewContentModeTop,
UIViewContentModeBottom,
UIViewContentModeLeft,
UIViewContentModeRight,
UIViewContentModeTopLeft,
UIViewContentModeTopRight,
UIViewContentModeBottomLeft,
UIViewContentModeBottomRight,
};

2. UIImage局部拉伸

// 按4邊間距顯示不拉伸的區(qū)域

• (UIImage *)resizableImageWithCapInsets:(UIEdgeInsets)capInsets NS_AVAILABLE_IOS(5_0);
  // 按2點(diǎn)拉伸
• (UIImage *)stretchableImageWithLeftCapWidth:(NSInteger)leftCapWidth topCapHeight:(NSInteger)topCapHeight;
• (UIImage *)resizableImageWithCapInsets:(UIEdgeInsets)capInsets resizingMode:(UIImageResizingMode)resizingMode;
  // 拉伸模式
  typedef NS_ENUM(NSInteger, UIImageResizingMode) {
  UIImageResizingModeTile,//進(jìn)行區(qū)域復(fù)制模式拉伸
  UIImageResizingModeStretch,//進(jìn)行漸變復(fù)制模式拉伸
  };

3.UIImage修改大小

//內(nèi)縮放，一條變等于最長(zhǎng)邊，另外一條小于等于最長(zhǎng)邊

• (UIImage *)scaleToSize:(CGSize)newSize {
  CGFloat width = self.size.width;
  CGFloat height= self.size.height;
  CGFloat newSizeWidth = newSize.width;
  CGFloat newSizeHeight= newSize.height;
  if (width <= newSizeWidth &&
  height <= newSizeHeight) {
  return self;
  }

  if (width == 0 || height == 0 || newSizeHeight == 0 || newSizeWidth == 0) {
  return nil;
  }
  CGSize size;
  if (width / height > newSizeWidth / newSizeHeight) {
  size = CGSizeMake(newSizeWidth, newSizeWidth * height / width);
  } else {
  size = CGSizeMake(newSizeHeight * width / height, newSizeHeight);
  }
  return [self drawImageWithSize:size];
  }

• (UIImage *)drawImageWithSize: (CGSize)size {
  CGSize drawSize = CGSizeMake(floor(size.width), floor(size.height));
  UIGraphicsBeginImageContext(drawSize);

  [self drawInRect:CGRectMake(0, 0, drawSize.width, drawSize.height)];
  UIImage *newImage = UIGraphicsGetImageFromCurrentImageContext();
  UIGraphicsEndImageContext();
  return newImage;
  }