I’lll dig up a utility class that I made for UIImage that has this as well as
others.
Cheers.
> On Nov 2, 2020, at 4:59 PM, Carl Hoefs via Cocoa-dev
> <cocoa-dev@lists.apple.com> wrote:
>
> How can I correctly scale a UIImage from 3264x2448 down to 640x480 pixels?
>
>
> I have an iOS app that interacts with a macOS server process. The iOS app
> takes a 3264x2448 camera image, scales it to 640x480 pixels, and makes a JPEG
> representation of it to send to the server:
>
> NSData *dataObj = UIImageJPEGRepresentation(origImage,0.5);
>
> The server reads the bytes, and creates an NSImage:
>
> NSImage *theImage = [[NSImage alloc] initWithData:imageData];
> NSBitmapImageRep *imageRep = [[NSBitmapImageRep alloc]
> initWithData:[theImage TIFFRepresentation]];
>
> But at this point, imageRep.pixelsWide=1280 and imageRep.pixelsHigh=960!
>
> If I write theImage to disk and look at it with Preview, it displays onscreen
> as 640x480 but Preview's Inspector Tool shows it to be 1280x960.
>
> On the iOS app side, here's the UIImage category method I'm using to scale
> the image:
>
> + (UIImage *)imageWithImage:(UIImage *)image
> scaledToSize:(CGSize)newSize
> {
> UIGraphicsBeginImageContextWithOptions(newSize, NO, 0.0);
> [image drawInRect:CGRectMake(0, 0, newSize.width, newSize.height)];
> UIImage *newImage = UIGraphicsGetImageFromCurrentImageContext();
> UIGraphicsEndImageContext();
> return newImage;
> }
>
> Any suggestions?
> -Carl
>
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