我正在由几个图层组成一个视图，其中一些是旋转的。这些图层的显示效果很好，但是当我尝试制作图像时，所有的旋转/变换都被忽略了。
例如，如果我有一个包含指向左侧的箭头图像的 CALayer，则在围绕 z 轴旋转（使用 CATransform3DMakeRotation）后，它指向顶部，并且图层正确显示。但是，如果我得到该层的图像（使用 renderInContext），箭头仍然指向左侧，忽略任何转换。
任何人都知道为什么，我该怎么做才能得到我想要的结果？:-)
示例代码：
// ViewController.m
#import "ViewController.h"
#import <QuartzCore/QuartzCore.h>
// Don't forget to add the QuartzCore framework to your target.
@interface ViewController ()
@end
@implementation ViewController
- (void)loadView {
self.view = [[UIView alloc] initWithFrame:[[UIScreen mainScreen] bounds]];
self.view.backgroundColor = [UIColor lightGrayColor];
}
- (void)viewDidLoad {
[super viewDidLoad];
// Get the arrow image (tip to the left, 50 x 50 pixels).
// (Download the image from here: http://www.4shared.com/photo/uQfor7vC/arrow.html )
UIImage *arrowImage = [UIImage imageNamed:@"arrow"];
// The arrow layer in it's starting orientation (tip to the left).
CGRect layerFrame = CGRectMake(50.0, 50.0, arrowImage.size.width, arrowImage.size.height);
CALayer *arrowLayerStart = [CALayer new];
arrowLayerStart.frame = layerFrame;
[arrowLayerStart setContents:(id)[arrowImage CGImage]];
[self.view.layer addSublayer:arrowLayerStart];
// The arrow layer rotated around the z axis by 90 degrees.
layerFrame.origin = CGPointMake(layerFrame.origin.x + layerFrame.size.width + 25.0, layerFrame.origin.y);
CALayer *arrowLayerZ90 = [CALayer new];
arrowLayerZ90.frame = layerFrame;
[arrowLayerZ90 setContents:(id)[arrowImage CGImage]];
arrowLayerZ90.transform = CATransform3DMakeRotation(M_PI/2.0, 0.0, 0.0, 1.0);
[self.view.layer addSublayer:arrowLayerZ90];
// Now make images of each of these layers and display them in a second row.
// The starting layer without any rotation.
UIGraphicsBeginImageContext(arrowLayerStart.frame.size);
[arrowLayerStart renderInContext:UIGraphicsGetCurrentContext()];
UIImage *arrowStartImage = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
layerFrame.origin = CGPointMake(arrowLayerStart.frame.origin.x,
arrowLayerStart.frame.origin.y + arrowLayerStart.frame.size.height + 25.0);
CALayer *arrowLayerStartCaptured = [CALayer new];
arrowLayerStartCaptured.frame = layerFrame;
[arrowLayerStartCaptured setContents:(id)[arrowStartImage CGImage]];
[self.view.layer addSublayer:arrowLayerStartCaptured];
// The second layer, rotated around the z axis by 90 degrees.
UIGraphicsBeginImageContext(arrowLayerZ90.frame.size);
[arrowLayerZ90 renderInContext:UIGraphicsGetCurrentContext()];
UIImage *arrowZ90Image = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
layerFrame.origin = CGPointMake(arrowLayerZ90.frame.origin.x,
arrowLayerZ90.frame.origin.y + arrowLayerZ90.frame.size.height + 25.0);
CALayer *arrowLayerZ90Captured = [CALayer new];
arrowLayerZ90Captured.frame = layerFrame;
[arrowLayerZ90Captured setContents:(id)[arrowZ90Image CGImage]];
[self.view.layer addSublayer:arrowLayerZ90Captured];
}
@end
// ViewController.h
#import <UIKit/UIKit.h>
@interface ViewController : UIViewController
@end
// AppDelegate.h
#import <UIKit/UIKit.h>
@interface AppDelegate : UIResponder <UIApplicationDelegate>
@property (strong, nonatomic) UIWindow *window;
@end
// AppDelegate.m
#import "AppDelegate.h"
#import "ViewController.h"
@implementation AppDelegate
@synthesize window = _window;
- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions {
self.window = [[UIWindow alloc] initWithFrame:[[UIScreen mainScreen] bounds]];
self.window.rootViewController = [[ViewController alloc] init];
[self.window makeKeyAndVisible];
return YES;
}
@end