以前一直对类似聊天气泡背景图片拉伸的设置纠结，不管如何设置UIEdgeInsets属性都不能正常设置，今天对以下几种情况进行了总结，如有需要的同学可进行参考：

项目地址：https://github.com/loverjiao0321/EdgeInsetsDemo

说明：

/**

1、UIEdgeInsets中的值都可以以像素为单位进行设置

2、测量凸起部分距离图片边缘值时，若有存在圆角部分，计算时最好将圆角部分出去，如: - (void)addDialogueLeft;方法中左侧凸起部分为12像素，图片额外含圆角部分8像素，则UIEdgeInsets中left和right值>= (12+8)计算

**/

/**

*添加左侧凸起背景图片

*/

leftDialogue

- (void)addDialogueLeft

{

UIImageView *bgImageView = [[UIImageView alloc] initWithFrame:CGRectMake(30, dialogueCount * (kDialogueSpace + kDialogueViewHeight), 315, kDialogueViewHeight)];

UIImage *image = [UIImage imageNamed:@"dialogueLeft"];

/*该图片尺寸为354*97

**1、凸起部分右侧距离图片左侧边缘大概为20(包括圆角部分宽度)，因此UIEdgeInsets中left和right值>= 20即可.(此值若不合适继续调大)

**2、不涉及上下距离，整体高度为97，因此UIEdgeInsets中top和bottom值<= 48即可.(此值若不合适继续调小)

*/

UIEdgeInsets insets = UIEdgeInsetsMake(45, 20, 45, 20);

UIImage *insetImage = [image resizableImageWithCapInsets:insets];

bgImageView.image = insetImage;

[self.view addSubview:bgImageView];

dialogueCount++;

}

/**

*添加右侧凸起背景图片

*/

rightDialogue

- (void)addDialogueRight

{

UIImageView*bgImageView = [[UIImageViewalloc]initWithFrame:CGRectMake(30,dialogueCount* (kDialogueSpace+kDialogueViewHeight),315,kDialogueViewHeight)];

UIImage*image = [UIImageimageNamed:@"dialogueRight"];

/*该图片尺寸为354*97

**1、凸起部分左侧距离图片右侧边缘大概为20(包括圆角部分宽度)，因此UIEdgeInsets中left和right值>= 20即可.(此值若不合适继续调大)

**2、不涉及上下距离，整体高度为97，因此UIEdgeInsets中top和bottom值<= 48即可.(此值若不合适继续调小)

*/

UIEdgeInsetsinsets =UIEdgeInsetsMake(45,20,45,20);

UIImage*insetImage = [imageresizableImageWithCapInsets:insets];

bgImageView.image= insetImage;

[self.viewaddSubview:bgImageView];

}

/**

*添加左上角凸起背景图片

*/

topLeftDialogue

- (void)addDialogueTopLeft

{

UIImageView*bgImageView = [[UIImageViewalloc]initWithFrame:CGRectMake(30,dialogueCount* (kDialogueSpace+kDialogueViewHeight),315,kDialogueViewHeight)];

UIImage*image = [UIImageimageNamed:@"dialogueTopLeft"];

/*该图片尺寸为343*106

**1、凸起部分右侧距离图片左侧边缘大概为27，因此UIEdgeInsets中left和right值>= 27即可.(此值若不合适继续调大)

**2、凸起部分底部图片高度（除去凸起高度）大概为98，因此UIEdgeInsets中top和bottom值<= 49即可.(此值若不合适继续调小)

*/

UIEdgeInsetsinsets =UIEdgeInsetsMake(40,27,40,27);

UIImage*insetImage = [imageresizableImageWithCapInsets:insets];

bgImageView.image= insetImage;

[self.viewaddSubview:bgImageView];

}

/**

*添加左下角凸起背景图片

*/

bottomLeftDialogue

- (void)addDialogueBottomLeft

{

UIImageView*bgImageView = [[UIImageViewalloc]initWithFrame:CGRectMake(30,dialogueCount* (kDialogueSpace+kDialogueViewHeight),315,kDialogueViewHeight)];

UIImage*image = [UIImageimageNamed:@"dialogueBottomLeft"];

/*该图片尺寸为343*106

**1、凸起部分右侧距离图片左侧边缘大概为23，因此UIEdgeInsets中left和right值>= 23即可.(此值若不合适继续调大)

**2、凸起部分底部图片高度（除去凸起高度）大概为97，因此UIEdgeInsets中top和bottom值<= 48即可.(此值若不合适继续调小)

*/

UIEdgeInsetsinsets =UIEdgeInsetsMake(40,23,40,23);

UIImage*insetImage = [imageresizableImageWithCapInsets:insets];

bgImageView.image= insetImage;

[self.viewaddSubview:bgImageView];

}

/**

*添加右上角凸起背景图片

*/

topRightDialogue

- (void)addDialogueTopRight

{

UIImageView*bgImageView = [[UIImageViewalloc]initWithFrame:CGRectMake(30,dialogueCount* (kDialogueSpace+kDialogueViewHeight),315,kDialogueViewHeight)];

UIImage*image = [UIImageimageNamed:@"dialogueTopRight"];

/*该图片尺寸为343*106

**1、凸起部分左侧距离图片右侧边缘大概为22，因此UIEdgeInsets中left和right值>= 22即可.(此值若不合适继续调大)

**2、凸起部分底部图片高度（除去凸起高度）大概为98，因此UIEdgeInsets中top和bottom值<= 49即可.(此值若不合适继续调小)

*/

UIEdgeInsetsinsets =UIEdgeInsetsMake(40,22,40,22);

UIImage*insetImage = [imageresizableImageWithCapInsets:insets];

bgImageView.image= insetImage;

[self.viewaddSubview:bgImageView];

}

/**

*添加右下角凸起背景图片

*/

bottomRightDialogue

- (void)addDialogueBottomRight

{

UIImageView*bgImageView = [[UIImageViewalloc]initWithFrame:CGRectMake(30,dialogueCount* (kDialogueSpace+kDialogueViewHeight),315,kDialogueViewHeight)];

UIImage*image = [UIImageimageNamed:@"dialogueBottomRight"];

/*该图片尺寸为343*106

**1、凸起部分左侧距离图片右侧边缘大概为54，因此UIEdgeInsets中left和right值>= 54即可.(此值若不合适继续调大)

**2、凸起部分底部图片高度（除去凸起高度）大概为96，因此UIEdgeInsets中top和bottom值<= 48即可.(此值若不合适继续调小)

*/

UIEdgeInsetsinsets =UIEdgeInsetsMake(45,54,45,54);

UIImage*insetImage = [imageresizableImageWithCapInsets:insets];

bgImageView.image= insetImage;

[self.viewaddSubview:bgImageView];

}