swift - 快速将原始图像数据转换为 jpeg

Question

我正在尝试将原始图像数据快速转换为 jpeg。但不幸的是，创建的 jpeg 图像是倾斜的。请在下面找到用于转换的代码。

let rawPtr = (rawImgData as NSData).bytes
let mutableRawPtr = UnsafeMutableRawPointer.init(mutating: rawPtr)
let context = CGContext.init(data: mutableRawPtr,
                             width: 750,
                             height: 1334,
                             bitsPerComponent: 32,
                             bytesPerRow: (8 * 750)/8,
                             space: CGColorSpaceCreateDeviceRGB(),
                             bitmapInfo: CGImageAlphaInfo.premultipliedLast.rawValue())
let imageRef = CGContext.makeImage(context!)
let imageRep = NSBitmapImageRep(cgImage: imageRef()!)
let finalData = imageRep.representation(using: .jpeg,
                                        properties: [NSBitmapImageRep.PropertyKey.compressionFactor : 0.5])

这是转换后的 jpeg 图像

任何帮助或指示将不胜感激。提前致谢!

Answer 1

终于找到答案了

var width:size_t?
var height:size_t?
let bitsPerComponent:size_t = 8
var bytesPerRow:size_t?
var bitmapInfo: UInt32
if #available(OSX 10.12, *) {
    bitmapInfo = UInt32(CGImageAlphaInfo.premultipliedFirst.rawValue) | UInt32(CGImageByteOrderInfo.order32Little.rawValue)
} else {
    bitmapInfo = UInt32(CGImageAlphaInfo.premultipliedFirst.rawValue)
}
let colorSpace = CGColorSpaceCreateDeviceRGB()

do {
    let streamAttributesFuture = self.bitmapStream?.streamAttributes()
    streamAttributesFuture?.onQueue(.main, notifyOfCompletion: { (streamAttributesFut) in

    })
    try streamAttributesFuture?.await()
    let dict = streamAttributesFuture?.result
    width = (dict?.attributes["width"] as! Int)
    height = (dict?.attributes["height"] as! Int)
    bytesPerRow = (dict?.attributes["row_size"] as! Int)

} catch let frameError{
    print("frame error = \(frameError)")
    return
}

let rawPtr = (data as NSData).bytes
let mutableRawPtr = UnsafeMutableRawPointer.init(mutating: rawPtr)
let context = CGContext.init(data: mutableRawPtr, width: width!, height: height!, bitsPerComponent: bitsPerComponent, bytesPerRow: bytesPerRow!, space: colorSpace, bitmapInfo: bitmapInfo)
if context == nil {
    return
}

let imageRef = context?.makeImage()

let scaledWidth = Int(Double(width!) / 1.5)
let scaledHeight = Int(Double(height!) / 1.5)

let resizeCtx = CGContext.init(data: nil, width: scaledWidth, height: scaledHeight, bitsPerComponent: bitsPerComponent, bytesPerRow: bytesPerRow!, space: colorSpace, bitmapInfo: bitmapInfo)
resizeCtx?.draw(imageRef!, in: CGRect(x: 0, y: 0, width: scaledWidth, height: scaledHeight))

resizeCtx?.interpolationQuality = .low

let resizedImgRef = resizeCtx?.makeImage()
let imageRep = NSBitmapImageRep(cgImage: resizedImgRef!)

let finalData = imageRep.representation(using: .jpeg, properties: [NSBitmapImageRep.PropertyKey.compressionFactor : compression])