我正试图将UIImage保存到NSData，然后在swift中将NSData读回新的UIImage。要将UIImage转换为NSData，我使用以下代码：
let imageData: NSData = UIImagePNGRepresentation(myImage)
如何将imageData（即NSData）转换回新的UIImage？
UIImage(data:imageData,scale:1.0)假设图像的比例为1。
谢谢。帮助了我很多。转换为Swift 3并且工作
保存：let data = UIImagePNGRepresentation(image)
要加载：let image = UIImage(data: data)
使用imageWithData:方法，它被转换为Swift为UIImage(data:)
let image : UIImage = UIImage(data: imageData)
现在在Swift 4.2中你可以使用pngData() UIImage的新实例方法从图像中获取数据
let profileImage = UIImage(named:"profile")!
let imageData = profileImage.pngData()
要另存为数据：
从StoryBoard，如果要在MainStoryBoard的imageView上保存“图像”数据，以下代码将起作用。
let image = UIImagePNGRepresentation(imageView.image!) as NSData?
将“image”加载到imageView：查看感叹号“！”，“？”密切关注这是否与此相同。
imageView.image = UIImage(data: image as! Data)
在此过程中，“NSData”类型会自动转换为“数据”类型。
为了安全执行代码，使用带有if-let的Data块来防止应用程序崩溃，并且函数UIImagePNGRepresentation返回一个可选值。
if let img = UIImage(named: "TestImage.png") {
if let data:Data = UIImagePNGRepresentation(img) {
// Handle operations with data here...
}
}
注意：数据是Swift 3+类。使用数据代替NSData和Swift 3+
通用图像操作（如png和jpg）：
if let img = UIImage(named: "TestImage.png") { //UIImage(named: "TestImage.jpg")
if let data:Data = UIImagePNGRepresentation(img) {
handleOperationWithData(data: data)
} else if let data:Data = UIImageJPEGRepresentation(img, 1.0) {
handleOperationWithData(data: data)
}
}
*******
func handleOperationWithData(data: Data) {
// Handle operations with data here...
if let image = UIImage(data: data) {
// Use image...
}
}
通过使用扩展名：
extension UIImage {
var pngRepresentationData: Data? {
return UIImagePNGRepresentation(self)
}
var jpegRepresentationData: Data? {
return UIImageJPEGRepresentation(self, 1.0)
}
}
*******
if let img = UIImage(named: "TestImage.png") { //UIImage(named: "TestImage.jpg")
if let data = img.pngRepresentationData {
handleOperationWithData(data: data)
} else if let data = img.jpegRepresentationData {
handleOperationWithData(data: data)
}
}
*******
func handleOperationWithData(data: Data) {
// Handle operations with data here...
if let image = UIImage(data: data) {
// Use image...
}
}
图像到数据： -
if let img = UIImage(named: "xxx.png") {
let pngdata = img.pngData()
}
if let img = UIImage(named: "xxx.jpeg") {
let jpegdata = img.jpegData(compressionQuality: 1)
}
数据到图像： -
let image = UIImage(data: pngData)
guard let image = UIImage(named: "img") else { return }
let jpegData = image.jpegData(compressionQuality: 1.0)
let pngData = image.pngData()
extension UIImage {
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
}
}
}
// about properties: https://developer.apple.com/documentation/imageio/1464962-cgimagedestinationaddimage
let options: NSDictionary = [
kCGImagePropertyOrientation: 6,
kCGImagePropertyHasAlpha: true,
kCGImageDestinationLossyCompressionQuality: 0.5
]
// https://developer.apple.com/documentation/mobilecoreservices/uttype/uti_image_content_types
guard let data = image.toData(options: options, type: kUTTypeJPEG) else { return }
let size = CGFloat(data.count)/1000.0/1024.0
print("\(size) mb")
extension UIImage {
func toJpegData (compressionQuality: CGFloat, hasAlpha: Bool = true, orientation: Int = 6) -> Data? {
guard cgImage != nil else { return nil }
let options: NSDictionary = [
kCGImagePropertyOrientation: orientation,
kCGImagePropertyHasAlpha: hasAlpha,
kCGImageDestinationLossyCompressionQuality: compressionQuality
]
return toData(options: options, type: .jpeg)
}
func toData (options: NSDictionary, type: ImageType) -> Data? {
guard cgImage != nil else { return nil }
return toData(options: options, type: type.value)
}
// about properties: https://developer.apple.com/documentation/imageio/1464962-cgimagedestinationaddimage
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
}
}
// https://developer.apple.com/documentation/mobilecoreservices/uttype/uti_image_content_types
enum ImageType {
case image // abstract image data
case jpeg // JPEG image
case jpeg2000 // JPEG-2000 image
case tiff // TIFF image
case pict // Quickdraw PICT format
case gif // GIF image
case png // PNG image
case quickTimeImage // QuickTime image format (OSType 'qtif')
case appleICNS // Apple icon data
case bmp // Windows bitmap
case ico // Windows icon data
case rawImage // base type for raw image data (.raw)
case scalableVectorGraphics // SVG image
case livePhoto // Live Photo
var value: CFString {
switch self {
case .image: return kUTTypeImage
case .jpeg: return kUTTypeJPEG
case .jpeg2000: return kUTTypeJPEG2000
case .tiff: return kUTTypeTIFF
case .pict: return kUTTypePICT
case .gif: return kUTTypeGIF
case .png: return kUTTypePNG
case .quickTimeImage: return kUTTypeQuickTimeImage
case .appleICNS: return kUTTypeAppleICNS
case .bmp: return kUTTypeBMP
case .ico: return kUTTypeICO
case .rawImage: return kUTTypeRawImage
case .scalableVectorGraphics: return kUTTypeScalableVectorGraphics
case .livePhoto: return kUTTypeLivePhoto
}
}
}
}
let compressionQuality: CGFloat = 0.4
guard let data = image.toJpegData(compressionQuality: compressionQuality) else { return }
printSize(of: data)
let options: NSDictionary = [
kCGImagePropertyHasAlpha: true,
kCGImageDestinationLossyCompressionQuality: compressionQuality
]
guard let data2 = image.toData(options: options, type: .png) else { return }
printSize(of: data2)
问题
图像表示将占用大量的CPU和内存资源。因此，在这种情况下，最好遵循以下几条规则：
- 不要在主队列上运行jpegData（compressionQuality :)
- 同时运行一个jpegData（compressionQuality :)
错误：
for i in 0...50 {
DispatchQueue.global(qos: .utility).async {
let quality = 0.02 * CGFloat(i)
//let data = image.toJpegData(compressionQuality: quality)
let data = image.jpegData(compressionQuality: quality)
let size = CGFloat(data!.count)/1000.0/1024.0
print("\(i), quality: \(quality), \(size.rounded()) mb")
}
}
对：
let serialQueue = DispatchQueue(label: "queue", qos: .utility, attributes: [], autoreleaseFrequency: .workItem, target: nil)
for i in 0...50 {
serialQueue.async {
let quality = 0.02 * CGFloat(i)
//let data = image.toJpegData(compressionQuality: quality)
let data = image.jpegData(compressionQuality: quality)
let size = CGFloat(data!.count)/1000.0/1024.0
print("\(i), quality: \(quality), \(size.rounded()) mb")
}
}