iOS 负载缩放 UIImage 从资产

Question

I'm implementing a react-native component for iOS and need to return a UIImage . What I have is return [UIImage imageNamed:@"myAsset"]; which is working but the image presented is way too small.

How can I load an asset image and make it bigger?

Another aspect is, that the impl returning the UIImage is invoked quite often for objects we draw onto the screen, but they are all the same, so scaling with every call is maybe not a good idea, but I have no idea how to make assets having a size. Last but not least, it's a PDF asset.

What I've tried is this...

So I search for image scaling and came here:

NSURL *url = [NSBundle.mainBundle URLForResource:@"myAsset" withExtension:nil];
NSData *data = [NSData dataWithContentsOfURL:url];
UIImage *image = [UIImage imageWithData:data scale:0.5];
return image;

but now url is nil and it's not working.

Then I found this:

UIImage *image = [UIImage imageNamed:@"myAsset"];
NSData *rawData = (__bridge NSData *) CGDataProviderCopyData(CGImageGetDataProvider(image.CGImage));

return [UIImage imageWithData:rawData scale:0.5];

Which is somehow also not working at all.

Now I hope maybe you can help me and thank you in advance.

Answer 1

func resizeImage(image: UIImage, newWidth: CGFloat, newHeight: CGFloat) -> UIImage {
    UIGraphicsBeginImageContext(CGSizeMake(newWidth, newHeight))
    image.drawInRect(CGRectMake(0, 0, newWidth, newHeight))
    let newImage = UIGraphicsGetImageFromCurrentImageContext()
    UIGraphicsEndImageContext()

    return newImage
}