iOS-图片拉伸技巧

jopen 8年前

iOS开发中我们会遇到渐变的背景,内容可变的流式标签,聊天气泡(QQ聊天气泡),由于内容是可变的,宽度和高度同样可变,这样就是导致每次出现的尺寸与之前不一样。如果是需要设置的比较的多,估计美工会烦死,同样也会额外增加的内存开销,所以这个知道一点图片拉伸的技巧会师我们的能使我们APP更加高效,代码更加简洁,事半功倍~从设置的角度来有四种方法可以实现~

Assets设置

首先我们有一个不规则的气泡按钮,大小是35*30,Slices选中水平和垂直方向的距离,宽高设置为1

设置完成之,我们设置Button的背景图片看下加载效果:

UIButton *button = [[UIButton alloc] initWithFrame:CGRectMake(80, 100, 100, 40)];      UIImage *buttonImage = [UIImage imageNamed:@"Question"];      [button setTitle:@"默认" forState:UIControlStateNormal];      [button addTarget:self action:@selector(buttonPressed:) forControlEvents: UIControlEventTouchUpInside];      [button setBackgroundImage:buttonImage forState:UIControlStateNormal];      [self.view addSubview:button];

模拟器加载效果:

第一个图片是我们需要加载效果,如果我们将Slices设置为None,我们看到的效果是这样的:

看到这里是不是感觉有点兴趣了,为什么设置了上面的选项就可以出现平铺的效果,稍微思考一下,我们在下面的一种方式中将找到答案~

iOS5之前的设置

上图的第二个按钮是我们通过代码设置,不是在Assets中设置,我们先来看一下实现代码:

//35*30      UIButton *nextButton = [[UIButton alloc] initWithFrame:CGRectMake(80, 180, 100, 40)];      [nextButton setTitle:@"iOS5之前" forState:UIControlStateNormal];      nextButton.layer.borderColor=[[UIColor redColor] CGColor];      nextButton.layer.borderWidth=1.0f;      UIImage *image = [UIImage imageNamed:@"Question"];      // 设置左边端盖宽度  rightCap=width - leftCapWidth - 1      NSInteger leftCapWidth = image.size.width * 0.5;      // 设置上边端盖高度  bottom=height - topCapWidth - 1      NSInteger topCapHeight = image.size.height * 0.5;      UIImage *newImage = [image stretchableImageWithLeftCapWidth:leftCapWidth topCapHeight:topCapHeight];      [nextButton setBackgroundImage:newImage forState:UIControlStateNormal];      [self.view addSubview:nextButton];

新建图片,设置按钮的背景图片,与一般设置没有什么区别,不过多了stretchableImageWithLeftCapWidth:方法,我们看一下API说明:

@interface UIImage(UIImageDeprecated)    // use resizableImageWithCapInsets: and capInsets.    - (UIImage *)stretchableImageWithLeftCapWidth:(NSInteger)leftCapWidth topCapHeight:(NSInteger)topCapHeight __TVOS_PROHIBITED;  @property(nonatomic,readonly) NSInteger leftCapWidth __TVOS_PROHIBITED;   // default is 0. if non-zero, horiz. stretchable. right cap is calculated as width - leftCapWidth - 1  @property(nonatomic,readonly) NSInteger topCapHeight __TVOS_PROHIBITED;   // default is 0. if non-zero, vert. stretchable. bottom cap is calculated as height - topCapWidth - 1    @end

我们需要设置拉伸区域具体图片的上方和左边的距离:

strechWidth=width-leftCapWidth-(width-leftCapWidth-1)=1

strechHeight=height-rightCaopWidth-( height - topCapWidth - 1 )=1

所以我们拉伸的区域是1*1,关于上面的leftCapWidth有人可能心里有疑问,为什么leftCapWidth = image.size.width * 0.5,为什么是0.5?自己最开始随便设置一个距离结果图片丑的要死,比如说我们左边设置0.2,上边设置为0.8,我们看到的效果是这样的:

这是极端情况,默认的情况下不管图片是如何的规则,中间的1*1区域是正方形,如果按照上面设置,我们会发现,上下左右四个点组成的图片是极其不规则,因此建议设置在中间,不过有的是有偏离一些也没有太多问题,比如说0.4,0.6对于比例设置大家如果有兴趣的可以之后下载代码,自行研究~

iOS5设置

stretchableImageWithLeftCapWidth在iOS5之后已经废弃,我们可以通过 resizableImageWithCapInsets来设置上下左右边距~

resizableImageWithCapInsets与之前的方法一样,同样是通过重置产生新的图片:

- (UIImage *)resizableImageWithCapInsets:(UIEdgeInsets)capInsets NS_AVAILABLE_IOS(5_0); // create a resizable version of this image. the interior is tiled when drawn.

UIEdgeInsets基本上UI中比较常见:

typedef struct UIEdgeInsets {      CGFloat top, left, bottom, right;  // specify amount to inset (positive) for each of the edges. values can be negative to 'outset'  } UIEdgeInsets;

图片效果参考模拟器的第三个按钮,设置代码如下:

UIImage *image = [UIImage imageNamed:@"Question"];      UIButton  *resizableButton=[[UIButton alloc]initWithFrame:CGRectMake(80, 250, 100, 40)];      [resizableButton setTitle:@"iOS5" forState:UIControlStateNormal];      // 设置端盖的值      CGFloat top = image.size.height * 0.5;      CGFloat left = image.size.width * 0.5;      CGFloat bottom = image.size.height * 0.5;      CGFloat right = image.size.width * 0.5;            UIEdgeInsets edgeInsets = UIEdgeInsetsMake(top, left, bottom, right);      //拉伸图片      UIImage *edgeImage = [image resizableImageWithCapInsets:edgeInsets];      //背景图片      [resizableButton setBackgroundImage:edgeImage forState:UIControlStateNormal];      [self.view addSubview:resizableButton];

iOS6设置

iOS6的设置方法和iOS5差不多,多了一个参数 UIImageResizingMode:

- (UIImage *)resizableImageWithCapInsets:(UIEdgeInsets)capInsets resizingMode:(UIImageResizingMode)resizingMode NS_AVAILABLE_IOS(6_0); // the interior is resized according to the resizingMode

UIImageResizingMode说明:

typedef NS_ENUM(NSInteger, UIImageResizingMode) {      UIImageResizingModeTile,平铺模式,通过重复显示UIEdgeInsets指定的矩形区域来填充图片
UIImageResizingModeStretch, };拉伸模式,通过拉伸UIEdgeInsets指定的矩形区域来填充图片

实际效果参考上图中的最后一个按钮:

UIImage *image = [UIImage imageNamed:@"Question"];      UIButton  *resizableButtonMode=[[UIButton alloc]initWithFrame:CGRectMake(80, 320, 180, 40)];      [resizableButtonMode setTitle:@"iOS6" forState:UIControlStateNormal];      [resizableButtonMode addTarget:self action:@selector(buttonPressed:) forControlEvents:UIControlEventTouchUpInside];      // 设置上左下右边距      CGFloat topMode= image.size.height * 0.5;      CGFloat leftMode= image.size.width * 0.5;      CGFloat bottomMode= image.size.height * 0.5;      CGFloat rightMode= image.size.width * 0.5;            UIEdgeInsets edgeInsetsMode= UIEdgeInsetsMake(topMode, leftMode, bottomMode, rightMode);            // 拉伸图片      UIImage *edgeModeImage = [image resizableImageWithCapInsets:edgeInsetsMode resizingMode:UIImageResizingModeStretch];  //    UIImage *edgeModeImage = [image resizableImageWithCapInsets:edgeInsetsMode resizingMode:UIImageResizingModeTile];            //设置图片      [resizableButtonMode setBackgroundImage:edgeModeImage forState:UIControlStateNormal];      [self.view addSubview:resizableButtonMode];

项目GitHub地址: https://github.com/SmallElephant/iOS-FEImageStrech

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来自: http://www.cnblogs.com/xiaofeixiang/p/5127793.html