//1. 实例化二维码滤镜
CIFilter*filter = [CIFilterfilterWithName:@"CIQRCodeGenerator"];
//2. 恢复滤镜的默认属性
[filtersetDefaults];
//3. 将字符串转换成NSData
NSData*data = [strdataUsingEncoding:NSUTF8StringEncoding];
//4. 通过KVO设置滤镜inputMessage数据
[filtersetValue:dataforKey:@"inputMessage"];
//5. 获得滤镜输出的图像
CIImage*outputImage= [filter outputImage];
//6. 将CIImage转换成UIImage,并放大显示
return[UIImageimageWithCIImage:outputImagescale:20.0orientation:UIImageOrientationUp];