无法在 swift 中压缩 tiff 文件

Question

我的应用程序需要使用 iPad 相机捕获纸质文档的快照并将其以 Tiff 格式传递给 REST API。

我尝试使用 "UIImagePickerController" 捕获图像并使用 CGImageDestinationRef 中的 "kUTTypeTIFF" 将其转换为 Tiff 格式。它在 ipad pro12.9 中生成大约 20 到 30 MB 的未压缩图像。

现在我正在尝试使用各种格式压缩图像，但我很困惑，因为在 swift tiff 压缩中找不到指南。

语言：Swift

拍照代码片段，

let chosenImage = info[UIImagePickerControllerOriginalImage] as! CGImage //2

let imgData = convertToTiffUsingUIImage(imgUI: info[UIImagePickerControllerOriginalImage] as! UIImage)

//Pass to REST
imageUploadRequest(imgData, uploadUrl: NSURL(string: "http://localhost:8080/user/service.jsp")!, param: ["userName": "xyz"])

self.dismissViewControllerAnimated(true, completion: nil);

转换为 tiff 图像

let key = kCGImagePropertyTIFFCompression
let value = 5

var keys = [ unsafeAddressOf(key) ]
var values = [ unsafeAddressOf(value) ]

var keyCallBacks = kCFTypeDictionaryKeyCallBacks
var valueCallBacks = kCFTypeDictionaryValueCallBacks

let cfDictionary = CFDictionaryCreate(kCFAllocatorDefault, &keys, &values, 1, &keyCallBacks, &valueCallBacks) 

let data = NSMutableData()

let dr: CGImageDestinationRef = CGImageDestinationCreateWithData(data, kUTTypeTIFF, 1, cfDictionary)!

CGImageDestinationAddImage(dr, imgUI.CGImage!, nil);

CGImageDestinationFinalize(dr);

print(data.length);

if data.length > 0 {
    UIImageWriteToSavedPhotosAlbum(UIImage(data:data)!, nil, nil, nil);
}

但这不会导致压缩图像。

谁能帮我理解 swift 中的 Tiff 文件压缩？

Answer 1

您不应该以 TIFF 形式传递照片。照片需要是 JPG，这是您应该使用的格式。换句话说，照片的压缩版本是 JPG。不要使用 TIFF 作为中介。

（最近有少数设备支持RAW，但你不能指望它。）

Answer 2

这是我对 this 答案中的代码进行转换的粗略尝试。

import Cocoa
import ImageIO
import CoreServices

func writeCCITTTiffWithCGImageURL(im: CGImage, url: CFURL)
{
   guard let colorSpace = CGColorSpace(name: CGColorSpace.genericGrayGamma2_2) else { print("Color space deosn't exist"); return }
   guard let bitmapCtx = CGContext(data: nil, width: im.width, height: im.height, bitsPerComponent: 8, bytesPerRow: 0, space: colorSpace, bitmapInfo: CGImageAlphaInfo.none.rawValue) else { print("Could not make bitmapContext"); return }

   bitmapCtx.draw(im, in: CGRect(x: 0, y: 0, width: im.width, height: im.height))
   guard let grayScaleImage: CGImage = bitmapCtx.makeImage()
   else { print("Could not make grayScale Image"); return }

   let tiffOptions: Dictionary<String, Int> = [String(kCGImagePropertyTIFFCompression) : 4]
   let options: NSDictionary = [String(kCGImagePropertyTIFFDictionary) : tiffOptions, kCGImagePropertyDepth : 1]

   guard let imageDestination = CGImageDestinationCreateWithURL(url, kUTTypeTIFF, 1, nil) else { print("Could not make imageDestination"); return }
   CGImageDestinationAddImage(imageDestination, grayScaleImage, options)
   CGImageDestinationFinalize(imageDestination)
}

Answer 3

这是示例：

   import UIKit
    
    import ImageIO
    
    import MobileCoreServices
    
    
    static func converterImgtoTIFF(img: UIImage) -> String{
            
            let options: NSDictionary =     [:]
            let convertToTIFF = img.toData(options: options, type: .tiff)
            guard let bmpData = convertToTIFF else {
                print(" ERROR: could not convert image to a bitmap bmpData var.")
                return ""
            }
            print("---------- convertToTIFF ----------------")
            let imagTiff = convertToTIFF?.base64EncodedString(options: .lineLength64Characters) ?? ""
           
            print("convert To TIFF =>>", imagTiff.count)
            
            return imagTiff
        }


extension UIImage {
    func toData (options: NSDictionary, type: ImageType) -> Data? {
        guard cgImage != nil else { return nil }
        return toData(options: options, type: type.value)
    }

    func toData (options: NSDictionary, type: CFString) -> Data? {
        guard let cgImage = cgImage else { return nil }
        return autoreleasepool { () -> Data? in
            let data = NSMutableData()
            guard let imageDestination = CGImageDestinationCreateWithData(data as CFMutableData, type, 1, nil) else { return nil }
            CGImageDestinationAddImage(imageDestination, cgImage, options)
            CGImageDestinationFinalize(imageDestination)
            return data as Data
        }
    }

    enum ImageType {
        case tiff // TIFF image
        var value: CFString {
            switch self {
            case .tiff: return kUTTypeTIFF
            }
        }
    }
}

无法在 swift 中压缩 tiff 文件

Unable to compress tiff file in swift

tiff

cgimage

ios

swift

拍照代码片段，

转换为 tiff 图像