浅说iOS二维码的那些事儿

1. 二维码需要用到 Quartz 2D 一般是三步走~1导入CoreImage框架,编写字符串转二维码图;2渲染二维码;3显示二维码.
   
   导入头文件
   
   #import <CoreImage/CoreImage.h>

2. 字符转二维码图
   
   代码如下:

/**
 *  创建二维码
 *
 *  @param string string 输入待转二维码的字符串
 *
 *  @return 二维码
 */
- (CIImage *)createTwoDimensionCodeWithString:(NSString *)string {

    CIFilter *filter = [CIFilter filterWithName:@"CIQRCodeGenerator"];

    [filter setDefaults];

    NSData *data = [ string dataUsingEncoding:NSUTF8StringEncoding];

    [filter setValue:data forKey:@"inputMessage"];

    CIImage *image = [filter outputImage];

    return image;
}

3.渲染改变

/**
 *  改变图片渲染
 *
 *  @param image 待渲染的二维码图片
 *  @param size  渲染大小
 *
 *  @return 返回渲染的二维码
 */

- (UIImage *)createNonInterpolatedUIImageFormCIImage:(CIImage *)image withSize:(CGFloat) size {
    CGRect extent = CGRectIntegral(image.extent);
    //设置比例
    CGFloat scale = MIN(size/CGRectGetWidth(extent), size/CGRectGetHeight(extent));
    // 创建bitmap（位图）;
    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);
    // 保存bitmap到图片
    CGImageRef scaledImage = CGBitmapContextCreateImage(bitmapRef);
    CGContextRelease(bitmapRef);
    CGImageRelease(bitmapImage);
    return [UIImage imageWithCGImage:scaledImage];
}

4.显示二维码

- (void)viewDidLoad {
    [super viewDidLoad];
    // Do any additional setup after loading the view, typically from a nib.

   CIImage *image = [self createTwoDimensionCodeWithString:@"爱我你怕了吗?"];
   // CIImage *image = [self createTwoDimensionCodeWithString:@"www.baidu.com"];
    UIImage *img = [self createNonInterpolatedUIImageFormCIImage:image withSize:300];
    UIImageView *imgView = [[UIImageView alloc]initWithImage:img];
    imgView.frame = CGRectMake(10, 50, 300, 300);
    [self.view addSubview:imgView];
}