[英]Downloading images and retina display
If I download some images from server should I resize it to support retina devises? 如果我从服务器下载一些图像,是否应该调整其大小以支持视网膜设计?
And if now I can not use -@2x, how can I set correct image to display? 如果现在不能使用-@ 2x,如何设置要显示的正确图像?
UPDATE: 更新:
If I cache images, I need to resize images after downloading and before caching, and cache 2 images, regular and @2x? 如果我缓存图像,则需要在下载后和缓存之前调整图像大小,并缓存2张常规图像和@ 2x?
your app should retrieved those image in retina size. 您的应用应以视网膜大小检索这些图像。 to get the non-retina size, you can scale it manually then save it.
要获得非视网膜尺寸,您可以手动缩放然后保存。 here the example code :
这里是示例代码:
UIImage *image = [UIImage imageNamed:@"yourRetinaImage@2x.png"];
// set non-retina size from current image
CGSize size = CGSizeMake(image.size.width / 2., image.size.height / 2.);
/** scale the image */
UIGraphicsBeginImageContext(size);
CGContextRef context = UIGraphicsGetCurrentContext();
CGContextTranslateCTM(context, 0.0, size.height);
CGContextScaleCTM(context, 1.0, -1.0);
CGContextDrawImage(context, CGRectMake(0.0f, 0.0f, size.width, size.height), image.CGImage);
UIImage *scaledImage = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
/** save scaled image */
NSString *basePath = [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) objectAtIndex:0];
// save with same name but without suffix "@2x"
NSString *filePath = [NSString stringWithFormat:@"%@/%@", basePath, @"yourRetinaImage"];
@try {
[UIImagePNGRepresentation(scaledImage) writeToFile:filePath options:NSAtomicWrite error:nil];
} @catch (NSException *exception) {
NSLog(@"error while saving non-retina image with exception %@", exception);
}
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