无法正确加载@2x的解决办法

bagusflyer — Tue, 19 Jul 2011 06:45:01 +0000

为使用retina显示，我们一般把图片的高分辨率版本存为@2x的形式，但是iOS 4.1以前的版本，如果使用imageWithContentsOfFile是无法保证@2x文件正确加载的。我使用如下方法解决此问题：

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// UIImage+Extras.h
@interface UIImage (Extras)

- (id)initWithContentsOfResolutionIndependentFile:(NSString *)path;
+ (UIImage*)imageWithContentsOfResolutionIndependentFile:(NSString *)path;

@end

// UIImage+Extras.m
- (id)initWithContentsOfResolutionIndependentFile:(NSString *)path {
if ( [[[UIDevice currentDevice] systemVersion] intValue] >= 4 && [[UIScreen mainScreen] scale] == 2.0 ) {
NSString *path2x = [[path stringByDeletingLastPathComponent]
stringByAppendingPathComponent:[NSString stringWithFormat:@"%@@2x.%@",
[[path lastPathComponent] stringByDeletingPathExtension],
[path pathExtension]]];

if ( [[NSFileManager defaultManager] fileExistsAtPath:path2x] ) {
return [self initWithCGImage:[[UIImage imageWithData:[NSData dataWithContentsOfFile:path2x]] CGImage] scale:2.0 orientation:UIImageOrientationUp];
}
}

return [self initWithData:[NSData dataWithContentsOfFile:path]];
}

+ (UIImage*)imageWithContentsOfResolutionIndependentFile:(NSString *)path {
return [[[UIImage alloc] initWithContentsOfResolutionIndependentFile:path] autorelease];
}

怎样从core graphics获取UIImage

bagusflyer — Mon, 06 Jul 2009 07:37:25 +0000

从core graphics获取UIImage的方法：

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- (void)viewDidLoad
{
[super viewDidLoad];

UIGraphicsBeginImageContext(CGSizeMake(20,20));
CGContextRef ctx = UIGraphicsGetCurrentContext();
CGContextBeginPath(ctx);
CGContextAddArc(ctx, 10, 10, 10, 0, 2*M_PI, 1);
CGContextSetRGBFillColor(ctx, 1,0, 0, 1);
CGContextFillPath(ctx);
UIImage *redBall = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
UIImageView *redBallView = [[UIImageView alloc] initWithImage:redBall];
redBallView.center = CGPointMake(160,330);
[self.view addSubview:redBallView];
}

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无法正确加载@2x的解决办法

怎样从core graphics获取UIImage