iOS实现图片折叠效果

//// ViewController.m// 图片折叠//// Created by llkj on 2017/8/31.// Copyright © 2017年 LayneCheung. All rights reserved.//#import "ViewController.h"@interface ViewController ()@property (weak, nonatomic) IBOutlet UIImageView *topImageV;@property (weak, nonatomic) IBOutlet UIImageView *buttomImageV;@property (nonatomic, weak) CAGradientLayer *gradientL;@end@implementation ViewController- (void)viewDidLoad {  [super viewDidLoad];  //1.让上不图片只显示上半部分  self.topImageV.layer.contentsRect = CGRectMake(0, 0, 1, 0.5);  //2.让下不图片只显示下半部分  self.buttomImageV.layer.contentsRect = CGRectMake(0, 0.5, 1, 0.5);  self.topImageV.layer.anchorPoint = CGPointMake(0.5, 1);  self.buttomImageV.layer.anchorPoint = CGPointMake(0.5, 0);  //设置渐变层  CAGradientLayer *gradidentL = [CAGradientLayer layer];  gradidentL.frame = self.buttomImageV.bounds;  gradidentL.opacity = 0;  gradidentL.colors = @[(id)[UIColor clearColor].CGColor, (id)[UIColor blackColor].CGColor];  self.gradientL = gradidentL;  [self.buttomImageV.layer addSublayer:gradidentL];}//这里也可以手动给大的ImageView添加一个UIPanGestureRecognizer手势- (IBAction)pan:(UIPanGestureRecognizer *)pan {  //获取移动的偏移量  CGPoint transP = [pan translationInView:pan.view];  //让上部图片开始旋转  CGFloat angle = transP.y * M_PI / 200;  //近大远小效果  CATransform3D transform = CATransform3DIdentity;  //眼睛离屏幕的距离(透视效果)  transform.m34 = -1 / 300.0;  self.gradientL.opacity = transP.y * 1 / 200.0;  self.topImageV.layer.transform = CATransform3DRotate(transform, -angle, 1, 0, 0);  if (pan.state == UIGestureRecognizerStateEnded) {    self.gradientL.opacity = 0;    //上部图片复位    //usingSpringWithDamping:弹性系数    [UIView animateWithDuration:0.5 delay:0 usingSpringWithDamping:0.5 initialSpringVelocity:0 options:UIViewAnimationOptionCurveLinear animations:^{      self.topImageV.layer.transform = CATransform3DIdentity;    } completion:^(BOOL finished) {    }];  }}@end