ios - CIImage大小范围为零？

Question

我创建了此类别，将CIImage转换为UIImage。我正在使用的CIImage来自CIFilter。

-(UIImage *)obtainImageWithRetinaScale:(CGFloat)scale
{
  CIContext *context = [CIContext contextWithOptions:nil];

  //CGRect frame = CGRectMake(0,0,700,392);
  CGImageRef processedCGImage = [context createCGImage:self
                                              fromRect:[self extent]];

  UIImage *returnImage = [UIImage imageWithCGImage:processedCGImage
                                    scale:scale
                              orientation:UIImageOrientationUp];
  CGImageRelease(processedCGImage);

  return returnImage;
}

运行此命令时， [self extent]给出的rect带有乱码，几乎没有(0、0，无穷大，无穷大)...那里真的有很大的数字。

显然处理的图像为零。

当我以正确的大小强制构图时，会正确生成图像。

Answer 1

使用以下代码，功劳完全归功于他的答案William Vasconcelos中的here，这就是为什么我将其设置为社区Wiki:

//assume beginImage is CIImage you want to tint            
CIImage* outputImage = nil;

//create some blue
CIFilter* blueGenerator = [CIFilter filterWithName:@"CIConstantColorGenerator"];
CIColor* blue = [CIColor colorWithString:@"0.1 0.5 0.8 1.0"];
[blueGenerator setValue:blue forKey:@"inputColor"];
CIImage* blueImage = [blueGenerator valueForKey:@"outputImage"];

//apply a multiply filter
CIFilter* filterm = [CIFilter filterWithName:@"CIMultiplyCompositing"];
[filterm setValue:blueImage forKey:@"inputImage"];
[filterm setValue:beginImage forKey:@"inputBackgroundImage"];
outputImage = [filterm valueForKey:@"outputImage"];

为了带来一些个人贡献并使之值得回答，以下是Swift 3版本:

// assume beginImage is the CIImage you want to tint
let outputImage: CIImage?
let blueGenerator = CIFilter(name: "CIConstantColorGenerator", withInputParameters: ["inputColor": CIColor(string: "0.1 0.5 0.8 1.0")])
let blueImage = blueGenerator!.outputImage

let filterM = CIFilter(name: "CIMultiplyCompositing", withInputParameters: ["inputImage": blueImage, "inputBackgroundImage": beginImage])
outputImage = filterM.outputImage