Filter 无法获取过滤器“；CICMYKHalftone“；

我只是试图修复过滤器“CICMYKHalftone”，但“*cMYKHalftone”并没有得到过滤器

 CIImage *inputImage = [[CIImage alloc] initWithImage: [UIImage      imageNamed:@"images.jpeg"]];
CIFilter *cMYKHalftone = [CIFilter filterWithName:@"CICMYKHalftone"];
[cMYKHalftone setDefaults]; 
[cMYKHalftone setValue:inputImage forKey:kCIInputImageKey];
[cMYKHalftone setValue:[CIVector vectorWithX:150 Y:150] forKey:@"inputCenter"];
[cMYKHalftone setValue:[NSNumber numberWithFloat:6.00] forKey:@"inputWidth"];
[cMYKHalftone setValue:[NSNumber numberWithFloat:0.00] forKey:@"inputAngle"];
[cMYKHalftone setValue:[NSNumber numberWithFloat:0.70] forKey:@"inputSharpness"];
[cMYKHalftone setValue:[NSNumber numberWithFloat:1.00] forKey:@"inputGCR"];
[cMYKHalftone setValue:[NSNumber numberWithFloat:0.50] forKey:@"inputUCR"];
CIImage *outputImage = [cMYKHalftone valueForKey:@"outputImage"];
CIContext *context = [CIContext contextWithOptions:nil];
theImageview.image = [UIImage imageWithCGImage:[context createCGImage:outputImage fromRect:outputImage.extent]];

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此筛选器不适用于iOS