You need a reverse image search. There are two main players in this business: Google and Tineye. Tineye was pretty cool till google arrived. Now, I prefer Google. Also, Tineye search is payed.

I have an example code for Google here. It must be not very difficult to rewrite it with Objective-C to use in iOS devices.

Press & hold the camera control button to open Visual Intelligence. Tap the shutter button to take a picture. The Ask button on the left sends it to ChatGPT. The Search button on the right does a Google reverse image search.

I completely agree with Othabit. It isn't that hard to understand that an iPhone or iPad user should be able to use reverse imaging search from the phone, without having to upload the picture to the computer. For example: a few days ago I was on a hike with some friends and we came across a strange plant of which I took a picture. I then tried to do a google reverse imaging search which I couldn't do because it is impossible with an apple devise. My friend with android was able to do it right there on the spot and we were able to identify the plant. It's little things like this that keep making me want to switch devises.

There's another question that seems fairly similar, here.

If I understood one of the answers here. Google has deprecated their imageSearch api. The answer also provides a link to a new api, Google Custom Search, but that seems to only have the option to send text and receive images as search results. There doesn't appear to be a reverse image search available. I did however come across a third-party api by Tineye that seems to have a mobile api and things ready to go. Check it out HERE!

Note: I have not tried, nor do I have any affiliations with Tineye, I just came across it and thought I'd offer a suggestion.

Update

After some serious searching, I have solution no. 1 based on the answer: here.

If you upload your image to a server or backend of some sort, and generate a URL, you can submit it this way:

NSString * yourImageURL = //...//;
NSString * searchURL = @"https://www.google.com/searchbyimage?&image_url="

NSString * completeURL = [NSString stringWithFormat:@"%@%@", searchURL, yourImageURL];

Good luck!

In the Google app you can use Lens and select a photo from your library. You need to tap the Lens icon and then tap the Photo icon next to the search button.