利用CoreImage生成二维码

使用CoreImage框架能够很轻松生成二维码。直接代码！

- (UIImage *)createQRCodeImageWithOriginalContent:(NSString *)content {
    if (!content.length) {
        return;
    }
    //二维码滤镜
    CIFilter *filter = [CIFilter filterWithName:@"CIQRCodeGenerator"];
    //恢复滤镜的默认属性
    [filter setDefaults];
    //将字符串转换成NSData
    NSData *data = [content dataUsingEncoding:NSUTF8StringEncoding];
    //通过KVO设置滤镜inputmessage数据
    [filter setValue:data forKey:@"inputMessage"];
    //获得滤镜输出的图像
    CIImage *outputImage = [filter outputImage];
    //将CIImage转换成UIImage,并放大显示
    return [self createNonInterpolatedUIImageFormCIImage:outputImage withSize:110.0];
}

//改变二维码大小
- (UIImage *)createNonInterpolatedUIImageFormCIImage:(CIImage *)image withSize:(CGFloat) size {
    CGRect extent = CGRectIntegral(image.extent);
    CGFloat scale = MIN(size/CGRectGetWidth(extent), size/CGRectGetHeight(extent));
    // 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);
    // 保存bitmap到图片
    CGImageRef scaledImage = CGBitmapContextCreateImage(bitmapRef);
    CGContextRelease(bitmapRef);
    CGImageRelease(bitmapImage);
    return [UIImage imageWithCGImage:scaledImage];
}

调用：

UIImage *img = [self createQRCodeImageWithOriginalContent:@"https://www.baidu.com"];
_avatar.image = img;
//如果还想加上阴影，就在ImageView的Layer上使用下面代码添加阴影
_avatar.layer.shadowOffset = CGSizeMake(0, 0.5);//设置阴影的偏移量
_avatar.layer.shadowRadius = 1;//设置阴影的半径
_avatar.layer.shadowColor = [UIColor blackColor].CGColor;//设置阴影的颜色为黑色
_avatar.layer.shadowOpacity = 0.3;

参考：
http://blog.csdn.net/qq_24307675/article/details/49817701