OC中生成二维码

作品链接：
http://www.jianshu.com/users/1e0f5e6f73f6/top_articles

CIFilter是在 <CoreImage/CoreImage.h>框架集成
   // 1.创建滤镜对象
    CIFilter *filter = [CIFilter filterWithName:@"CIQRCodeGenerator"];
    
    // 2.恢复默认设置
    [filter setDefaults];
    
    // 3.设置数据
    NSString *info = @"http://www.taobao.com";
    NSData *infoData = [info dataUsingEncoding:NSUTF8StringEncoding];
    [filter setValue:infoData forKey:@"inputMessage"];
    // 4.生成二维码
    CIImage *outputImage = [filter outputImage];
    self.imageView.image = [self createNonInterpolatedUIIamgeFormCIImage:outputImage withSize:300];

- 生成清晰的二维码

/**
 *  根据CIImage生成指定大小的UIImage 生成清晰的二维码
 *
 *  @param image CIImage
 *  @param size  图片宽度
 */
- (UIImage *)createNonInterpolatedUIIamgeFormCIImage:(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 = CGColorSpaceCreateDeviceCMYK();
    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
    CGImageRef scaledImage = CGBitmapContextCreateImage(bitmapRef);
    CGContextRelease(bitmapRef);
    CGImageRelease(bitmapImage);
    return [UIImage imageWithCGImage:scaledImage];
}