二维码生成（利用iOS CoreImage框架）

//
//  ViewController.m

#import "ViewController.h"
#import <CoreImage/CoreImage.h> //导入框架

@interface ViewController ()

@property (weak, nonatomic) IBOutlet UIImageView *qrcodeView;
@end

@implementation ViewController

- (void)viewDidLoad {
[super viewDidLoad];
}

- (void)touchesBegan:(NSSet<UITouch *> *)touches withEvent:(UIEvent *)event
{
CIFilter *filter = [CIFilter filterWithName:@"CIQRCodeGenerator"];
// 2、恢复滤镜的默认属性
[filter setDefaults];
// 3、设置内容
NSString *str = @"这是一个二维码的生成结果";
NSData *data = [str dataUsingEncoding:NSUTF8StringEncoding];
// 使用KVO设置属性
[filter setValue:data forKey:@"inputMessage"];
// 4、获取输出文件
CIImage *outputImage = [filter outputImage];
// 5、显示二维码
UIImage *image =[self createNonInterpolatedUIImageFormCIImage:outputImage withSize:500.0f];
self.qrcodeView.image =image;

}
- (UIImage *)createNonInterpolatedUIImageFormCIImage:(CIImage *)image withSize:(CGFloat) size
{
CGRect extent = CGRectIntegral(image.extent);
CGFloat scale = MIN(size/CGRectGetWidth(extent), size/CGRectGetHeight(extent));
// 1.创建bitmap;
size_t width = CGRectGetWidth(extent) * scale;
size_t height = CGRectGetHeight(extent) * scale;
CGColorSpaceRef cs = CGColorSpaceCreateDeviceGray();
CGContextRef bitmapRef = CGBitmapContextCreate(nil, width, height, 8, 0, cs, (CGBitmapInfo)kCGImageAlphaNone);
CIContext *context = [CIContext contextWithOptions:nil];
CGImageRef bitmapImage = [context createCGImage:image fromRect:extent];
CGContextSetInterpolationQuality(bitmapRef, kCGInterpolationNone);
CGContextScaleCTM(bitmapRef, scale, scale);
CGContextDrawImage(bitmapRef, extent, bitmapImage);
// 2.保存bitmap到图片
CGImageRef scaledImage = CGBitmapContextCreateImage(bitmapRef);
CGContextRelease(bitmapRef);
CGImageRelease(bitmapImage);
return [UIImage imageWithCGImage:scaledImage];
}
@end