Core Image ciContext.writeHEIFRepresentation() 在使用 CICrop 过滤器时生成带有对角线的图像。我怎样才能防止这种情况？

Question

我正在尝试生成 HEIF 输出文件，但这样做时会得到奇怪的对角线。其他输出格式都没有出现这些奇怪的线条。见下图。问题似乎正在裁剪，但错误仅显示在 HEIF 输出文件中。

我可以使用以下操场代码复制此代码，您可以从这里下载 https://duncangroenewald.com/files/SampleApps/CoreImageHEIFExporterBug-2.zip

我有一份 Apple 的错误报告，他们提到了“亚像素错误”——我不知道那是什么，或者为什么这些只会在 heif 输出格式中体现出来，或者如何防止它们——任何想法或这样做只是看起来像是 Apple 代码中的错误？

编辑。需要明确的是，这不是操场问题，因为问题发生在 macOS 应用程序中。

我怀疑在生成 HEIF 输出时这一定是 CIContext 错误，因为它仅在 heif 输出文件中出现。但是，我对亚像素错误或 Apple 认为它们应该与此问题相关的原因一无所知。也许有更多Core Image知识的人可以提出一些可能的解决方案。

import Cocoa

let files = ["/Users/duncangroenewald/Development/Playgrounds/CoreImageHEIFExporterBug/DSC02022.ARW",
     "/Users/duncangroenewald/Development/Playgrounds/CoreImageHEIFExporterBug/DSC02018.ARW"
]

let destFilePath = "/Users/duncangroenewald/Development/Playgrounds/CoreImageHEIFExporterBug"

let destUrl = URL(fileURLWithPath: destFilePath)

let exporter = Exporter()

var crops = [CGRect(x: 0, y: 0, width: 5310, height: 3212),
             CGRect(x: 0, y: 0, width: 5311, height: 3212),
             CGRect(x: 0, y: 0, width: 5312, height: 3212),
             CGRect(x: 0, y: 0, width: 5313, height: 3212)]


for file in files {
    exporter.processRAWFile(file, destPath: destFilePath, crops: crops)
}

print("Done!")

import AppKit
import CoreImage
import CoreImage.CIFilterBuiltins
import OSLog

public class Exporter {
    
    var formats: [String] = ["heif", "png"]
    
    // Get the CIContext
    let ciContext = CIContext()
    
    var imageOrientation: Int = 0
    var imageNativeSize: CGSize = .zero

    var crops: [CGRect] = [.zero]

    public init() {
        
    }
    
    public func processRAWFile(_ path: String, destPath: String, crops: [CGRect]) {
        
        print("processRAWFile XXX")
        self.crops = crops
        
        let url = URL(fileURLWithPath: path)
        
        let filename = url.deletingPathExtension().lastPathComponent
        
        let destDirUrl = URL(fileURLWithPath: destPath)
        print("destDirUrl: \(destDirUrl)")
        
        for crop in crops {
        
            let cropName = "\(filename)_\(crop.width)x\(crop.height)_\(useDefaultRAW ? "default" : "")"
        
            for format in formats {
            let destUrl = destDirUrl.appendingPathComponent(cropName).appendingPathExtension(format)
            print("destFile: \(destUrl)")
        
                self.exportFile(url: url, destUrl: destUrl, crop: crop, format: format)
                
            }
          
        }
    }
    
    func exportFile(url: URL, destUrl: URL, crop: CGRect, format: String){
        print("exportFile \(url)")
        print("destFile: \(destUrl)")
        
        guard let rawFilter = CIFilter(imageURL: url, options: nil), let outputImage = rawFilter.outputImage else {
            print("Failed to load \(url.lastPathComponent) for exporting")
            return
        }
        
        let processImage = self.crop(outputImage, rect: crop)
        
        
        let options = [kCGImageDestinationLossyCompressionQuality as CIImageRepresentationOption: 1.0 as CGFloat]
        let colorSpace = CGColorSpace(name: CGColorSpace.sRGB)!
        let imgFormat = CIFormat.RGBA16
        
        do {
            
            switch format {
            case "tiff":
                try ciContext.writeTIFFRepresentation(of: processImage, to: destUrl, format: imgFormat, colorSpace: colorSpace, options: options)
            case "jpeg":
                try ciContext.writeJPEGRepresentation(of: processImage, to: destUrl, colorSpace: colorSpace, options: options)
            case "png":
                try ciContext.writePNGRepresentation(of: processImage, to: destUrl, format: imgFormat, colorSpace: colorSpace, options: options)
            case "heif":
                try ciContext.writeHEIFRepresentation(of: processImage, to: destUrl, format: imgFormat, colorSpace: colorSpace, options: options)
            default:
                try ciContext.writePNGRepresentation(of: processImage, to: destUrl, format: imgFormat, colorSpace: colorSpace, options: options)
            }
            
        } catch {
            print("Error exporting \(format): \(error.localizedDescription)")
        }
        
    }
    var useDefaultRAW: Bool = true

    func crop(_ ciImage: CIImage, rect: CGRect)->CIImage {
        if let cropped = self.cropFilter(ciImage, rect: rect) {
            return cropped
        } else {
            print("Error cropping image !")
            return ciImage
        }
    }
  
    
    func cropFilter(_ input: CIImage, rect: CGRect) -> CIImage? {
        
        
        // Getting a dashed border !!
        guard let cropFilter = CIFilter(name: "CICrop") else {
            print("Error no CICrop filter found !")
            return input
        }
        let ciVect = CIVector(cgRect: rect)
        cropFilter.setValue(input, forKey: kCIInputImageKey)

        cropFilter.setValue(ciVect, forKey: "inputRectangle")

        return cropFilter.value(forKey: kCIOutputImageKey) as? CIImage
        
    }
}

Answer 1

我能找到解决它的唯一方法是 先通过上下文渲染CGImage，然后从CGImage重新创建CIImage。

编辑

let context = CIContext()
let fileURL = <URL to save location>
let ciImage = <Here is the image you got as output of filter>
let options = [kCGImageDestinationLossyCompressionQuality as CIImageRepresentationOption: 1.0 as CGFloat]
let colorSpace = CGColorSpace(name: CGColorSpace.sRGB)!
let imgFormat = CIFormat.RGBA16

// First we create a CGImage
let cgImage = context.createCGImage(ciImage, 
                                    from: ciImage.extent,
                                    format: imgFormat,
                                    colorSpace: colorSpace)

// Then we use this CGImage to re-create CIImage and save it
try context.writeHEIFRepresentation(
                of: CIImage(cgImage: cgImage),
                to: fileURL,
                format: imgFormat,
                colorSpace: colorSpace,
                options: options
            )