iOS图片拉伸的多种方式

typedef NS_ENUM(NSInteger, UIViewContentMode) { UIViewContentModeScaleToFill,   // 默认 拉伸（会变形） UIViewContentModeScaleAspectFit,  // 等比例拉伸 UIViewContentModeScaleAspectFill,  // 等比例填充 UIViewContentModeRedraw,    // redraw on bounds change (这个不清楚)  UIViewContentModeCenter,    // 下面的就是不拉伸按位置显示了 UIViewContentModeTop, UIViewContentModeBottom, UIViewContentModeLeft, UIViewContentModeRight, UIViewContentModeTopLeft, UIViewContentModeTopRight, UIViewContentModeBottomLeft, UIViewContentModeBottomRight,};

// 按4边间距显示不拉伸的区域- (UIImage *)resizableImageWithCapInsets:(UIEdgeInsets)capInsets NS_AVAILABLE_IOS(5_0); // 按2点拉伸- (UIImage *)stretchableImageWithLeftCapWidth:(NSInteger)leftCapWidth topCapHeight:(NSInteger)topCapHeight;- (UIImage *)resizableImageWithCapInsets:(UIEdgeInsets)capInsets resizingMode:(UIImageResizingMode)resizingMode;// 拉伸模式typedef NS_ENUM(NSInteger, UIImageResizingMode) { UIImageResizingModeTile,//进行区域复制模式拉伸 UIImageResizingModeStretch,//进行渐变复制模式拉伸};

//内缩放，一条变等于最长边，另外一条小于等于最长边- (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;}