文字识别，iOS12系统就已经加入了文字识别能力，但是对于中国的开发者来说用处很小，因为不支持汉语识别，iOS15系统解决了汉语识别问题，基本OC代码如下，
VNRecognizeTextRequest *textRequest = [[VNRecognizeTextRequest alloc] initWithCompletionHandler:^(VNRequest * _Nonnull request, NSError * _Nullable error) {
NSArray *observations = request.results;
[self textRectangles:observations image:image complete:complete];
NSLog(@"%@",observations);
}];
textRequest.recognitionLevel = VNRequestTextRecognitionLevelAccurate;
textRequest.usesLanguageCorrection = NO;
textRequest.recognitionLanguages = @[@"zh-Hans", @"en-US"];
// 转换CIImage
CIImage *convertImage = [[CIImage alloc]initWithImage:image];
// 创建处理requestHandler
VNImageRequestHandler *detectRequestHandler = [[VNImageRequestHandler alloc]initWithCIImage:convertImage options:@{}];
// 发送识别请求
[detectRequestHandler performRequests:@[textRequest] error:nil];
需要注意的有两点，低一点就是识别的等级，一个是精准，一个是快速，
第二点就是识别语言的先后顺序问题，因为识别是第一种语言失败后去识别第二种语言
