如何在上传到Parse之前压缩缩小图像的大小为PFFile？(迅速)
elv*_*lkm 76 uiimage ios parse-platform swift
我正试图在手机上直接拍照后将图像文件上传到Parse.但它引发了一个例外:
由于未捕获的异常'NSInvalidArgumentException'终止应用程序,原因:'PFFile不能大于10485760字节'
这是我的代码:
在第一个视图控制器:
override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?) {
if (segue.identifier == "getImage")
{
var svc = segue.destinationViewController as! ClothesDetail
svc.imagePassed = imageView.image
}
}
在上传图像的视图控制器中:
let imageData = UIImagePNGRepresentation(imagePassed)
let imageFile = PFFile(name: "\(picName).png", data: imageData)
var userpic = PFObject(className:"UserPic")
userpic["picImage"] = imageFile`
但我仍然需要将该照片上传到Parse.有没有办法减小图像的大小或分辨率？
Leo*_*bus 168
是的,您可以使用UIImageJPEGRepresentation而不是UIImagePNGRepresentation减少图像文件大小.您可以按如下方式创建扩展UIImage:
Xcode 8.2•Swift 3.0.2
extension UIImage {
enum JPEGQuality: CGFloat {
case lowest = 0
case low = 0.25
case medium = 0.5
case high = 0.75
case highest = 1
}
/// Returns the data for the specified image in JPEG format.
/// If the image object’s underlying image data has been purged, calling this function forces that data to be reloaded into memory.
/// - returns: A data object containing the JPEG data, or nil if there was a problem generating the data. This function may return nil if the image has no data or if the underlying CGImageRef contains data in an unsupported bitmap format.
func jpeg(_ quality: JPEGQuality) -> Data? {
return UIImageJPEGRepresentation(self, quality.rawValue)
}
}
编辑/更新:
Xcode 10 Swift 4.2
extension UIImage {
enum JPEGQuality: CGFloat {
case lowest = 0
case low = 0.25
case medium = 0.5
case high = 0.75
case highest = 1
}
/// Returns the data for the specified image in JPEG format.
/// If the image object’s underlying image data has been purged, calling this function forces that data to be reloaded into memory.
/// - returns: A data object containing the JPEG data, or nil if there was a problem generating the data. This function may return nil if the image has no data or if the underlying CGImageRef contains data in an unsupported bitmap format.
func jpeg(_ jpegQuality: JPEGQuality) -> Data? {
return jpegData(compressionQuality: jpegQuality.rawValue)
}
}
用法:
if let imageData = image.jpeg(.lowest) {
print(imageData.count)
}
- 除语法之外没有区别.当然你可以手动编写代码`UIImageJPEGRepresentation(yourImage,1.0)`而不只是输入`.jp`并让xcode为你自动完成方法.压缩枚举`.whatever`是一样的. (2认同)
gbk*_*gbk 44
如果你想将图像的大小限制为一些具体的值,你可以这样做:
import UIKit
extension UIImage {
// MARK: - UIImage+Resize
func compressTo(_ expectedSizeInMb:Int) -> UIImage? {
let sizeInBytes = expectedSizeInMb * 1024 * 1024
var needCompress:Bool = true
var imgData:Data?
var compressingValue:CGFloat = 1.0
while (needCompress && compressingValue > 0.0) {
if let data:Data = UIImageJPEGRepresentation(self, compressingValue) {
if data.count < sizeInBytes {
needCompress = false
imgData = data
} else {
compressingValue -= 0.1
}
}
}
if let data = imgData {
if (data.count < sizeInBytes) {
return UIImage(data: data)
}
}
return nil
}
}
- 这是非常昂贵的你在while循环和每次做这么重的任务!无限制条件.. (9认同)
- 这是一个非常糟糕的主意，它充满了可怕的边缘情况。1) 它从 compressingValue 1.0 开始，这意味着几乎没有任何压缩。如果图像尺寸很小，那么图像最终的 KB 大小将远远超过其所需的大小。2）如果图像很大，它会很慢，因为它可能会重新压缩多次以达到目标大小。3）如果图像非常大，那么它可能会压缩到图像看起来很垃圾的程度。在这些情况下，最好只是不保存图像并告诉用户图像太大。 (3认同)
Jus Fixing for Xcode 7,于2015年9月21日测试并正常工作:
只需创建一个扩展UIImage如下:
extension UIImage
{
var highestQualityJPEGNSData: NSData { return UIImageJPEGRepresentation(self, 1.0)! }
var highQualityJPEGNSData: NSData { return UIImageJPEGRepresentation(self, 0.75)!}
var mediumQualityJPEGNSData: NSData { return UIImageJPEGRepresentation(self, 0.5)! }
var lowQualityJPEGNSData: NSData { return UIImageJPEGRepresentation(self, 0.25)!}
var lowestQualityJPEGNSData: NSData { return UIImageJPEGRepresentation(self, 0.0)! }
}
然后你可以像这样使用它:
let imageData = imagePassed.lowestQualityJPEGNSData
//image compression
func resizeImage(image: UIImage) -> UIImage {
var actualHeight: Float = Float(image.size.height)
var actualWidth: Float = Float(image.size.width)
let maxHeight: Float = 300.0
let maxWidth: Float = 400.0
var imgRatio: Float = actualWidth / actualHeight
let maxRatio: Float = maxWidth / maxHeight
let compressionQuality: Float = 0.5
//50 percent compression
if actualHeight > maxHeight || actualWidth > maxWidth {
if imgRatio < maxRatio {
//adjust width according to maxHeight
imgRatio = maxHeight / actualHeight
actualWidth = imgRatio * actualWidth
actualHeight = maxHeight
}
else if imgRatio > maxRatio {
//adjust height according to maxWidth
imgRatio = maxWidth / actualWidth
actualHeight = imgRatio * actualHeight
actualWidth = maxWidth
}
else {
actualHeight = maxHeight
actualWidth = maxWidth
}
}
let rect = CGRectMake(0.0, 0.0, CGFloat(actualWidth), CGFloat(actualHeight))
UIGraphicsBeginImageContext(rect.size)
image.drawInRect(rect)
let img = UIGraphicsGetImageFromCurrentImageContext()
let imageData = UIImageJPEGRepresentation(img!,CGFloat(compressionQuality))
UIGraphicsEndImageContext()
return UIImage(data: imageData!)!
}
func jpegData(compressionQuality: CGFloat) -> Data?如果您不需要压缩到特定大小，则使用效果很好。但是，对于某些图像，我发现能够压缩到特定文件大小以下很有用。在这种情况下，jpegData是不可靠的，并且图像的迭代压缩会导致文件大小趋于平稳（并且可能非常昂贵）。相反，我更喜欢减小 UIImage 本身的大小，然后转换为 jpegData 并检查减小的大小是否低于我选择的值（在我设置的误差范围内）。我根据当前文件大小与所需文件大小的比率调整压缩步长乘数，以加速最昂贵的第一次迭代。
斯威夫特 5
extension UIImage {
func resized(withPercentage percentage: CGFloat, isOpaque: Bool = true) -> UIImage? {
let canvas = CGSize(width: size.width * percentage, height: size.height * percentage)
let format = imageRendererFormat
format.opaque = isOpaque
return UIGraphicsImageRenderer(size: canvas, format: format).image {
_ in draw(in: CGRect(origin: .zero, size: canvas))
}
}
func compress(to kb: Int, allowedMargin: CGFloat = 0.2) -> Data {
let bytes = kb * 1024
var compression: CGFloat = 1.0
let step: CGFloat = 0.05
var holderImage = self
var complete = false
while(!complete) {
if let data = holderImage.jpegData(compressionQuality: 1.0) {
let ratio = data.count / bytes
if data.count < Int(CGFloat(bytes) * (1 + allowedMargin)) {
complete = true
return data
} else {
let multiplier:CGFloat = CGFloat((ratio / 5) + 1)
compression -= (step * multiplier)
}
}
guard let newImage = holderImage.resized(withPercentage: compression) else { break }
holderImage = newImage
}
return Data()
}
}
和用法：
let data = image.compress(to: 300)
UIImageresized扩展来自：
How do I resize the UIImage to reduce upload image size
Swift 4 二进制压缩图像的方法
我相信现在回答这个问题已经很晚了，但这是我对优化问题的解决方案我正在使用二进制搜索来找到最佳值。因此，例如，假设通过正常减法方法达到 62% 需要 38 次压缩尝试，*二元搜索**方法将在 max log(100) = 大约 7 次尝试中达到所需的解决方案。
但是，还要通知您，该UIImageJPEGRepresentation函数的行为不是线性的，尤其是当数字接近 1 时。这是屏幕截图，我们可以看到图像在浮点值 > 0.995 后停止压缩。这种行为是非常不可预测的，所以最好有一个可以处理这种情况的增量缓冲区。
这是它的代码
extension UIImage {
func resizeToApprox(sizeInMB: Double, deltaInMB: Double = 0.2) -> Data {
let allowedSizeInBytes = Int(sizeInMB * 1024 * 1024)
let deltaInBytes = Int(deltaInMB * 1024 * 1024)
let fullResImage = UIImageJPEGRepresentation(self, 1.0)
if (fullResImage?.count)! < Int(deltaInBytes + allowedSizeInBytes) {
return fullResImage!
}
var i = 0
var left:CGFloat = 0.0, right: CGFloat = 1.0
var mid = (left + right) / 2.0
var newResImage = UIImageJPEGRepresentation(self, mid)
while (true) {
i += 1
if (i > 13) {
print("Compression ran too many times ") // ideally max should be 7 times as log(base 2) 100 = 6.6
break
}
print("mid = \(mid)")
if ((newResImage?.count)! < (allowedSizeInBytes - deltaInBytes)) {
left = mid
} else if ((newResImage?.count)! > (allowedSizeInBytes + deltaInBytes)) {
right = mid
} else {
print("loop ran \(i) times")
return newResImage!
}
mid = (left + right) / 2.0
newResImage = UIImageJPEGRepresentation(self, mid)
}
return UIImageJPEGRepresentation(self, 0.5)!
}
}
新的更好的方式
import UIKit
extension UIImage {
func compress(maxKb: Double) -> Data? {
let quality: CGFloat = maxKb / self.sizeAsKb()
let compressedData: Data? = self.jpegData(compressionQuality: quality)
return compressedData
}
func sizeAsKb() -> Double {
Double(self.pngData()?.count ?? 0 / 1024)
}
}
// To use
let compressedImage = image.compress(maxKb: 100)
老坏方法
UIImage扩展起来非常简单
extension UIImage {
func resizeByByte(maxByte: Int, completion: @escaping (Data) -> Void) {
var compressQuality: CGFloat = 1
var imageData = Data()
var imageByte = UIImageJPEGRepresentation(self, 1)?.count
while imageByte! > maxByte {
imageData = UIImageJPEGRepresentation(self, compressQuality)!
imageByte = UIImageJPEGRepresentation(self, compressQuality)?.count
compressQuality -= 0.1
}
if maxByte > imageByte! {
completion(imageData)
} else {
completion(UIImageJPEGRepresentation(self, 1)!)
}
}
环球银行金融电信协会5
extension UIImage {
func resizeByByte(maxByte: Int, completion: @escaping (Data) -> Void) {
var compressQuality: CGFloat = 1
var imageData = Data()
var imageByte = self.jpegData(compressionQuality: 1)?.count
while imageByte! > maxByte {
imageData = self.jpegData(compressionQuality: compressQuality)!
imageByte = self.jpegData(compressionQuality: compressQuality)?.count
compressQuality -= 0.1
}
if maxByte > imageByte! {
completion(imageData)
} else {
completion(self.jpegData(compressionQuality: 1)!)
}
}
}
使用
// max 300kb
image.resizeByByte(maxByte: 300000) { (resizedData) in
print("image size: \(resizedData.count)")
}
- 非常慢且同步 (4认同)
斯威夫特 4.2 更新。我创建这个扩展是为了减小 UIImage 的大小。
这里有两种方法，第一种取百分比，第二种将图像缩小到 1MB。
当然你可以将第二种方法更改为1KB或任何你想要的大小。
import UIKit
extension UIImage {
func resized(withPercentage percentage: CGFloat) -> UIImage? {
let canvasSize = CGSize(width: size.width * percentage, height: size.height * percentage)
UIGraphicsBeginImageContextWithOptions(canvasSize, false, scale)
defer { UIGraphicsEndImageContext() }
draw(in: CGRect(origin: .zero, size: canvasSize))
return UIGraphicsGetImageFromCurrentImageContext()
}
func resizedTo1MB() -> UIImage? {
guard let imageData = self.pngData() else { return nil }
let megaByte = 1000.0
var resizingImage = self
var imageSizeKB = Double(imageData.count) / megaByte // ! Or devide for 1024 if you need KB but not kB
while imageSizeKB > megaByte { // ! Or use 1024 if you need KB but not kB
guard let resizedImage = resizingImage.resized(withPercentage: 0.5),
let imageData = resizedImage.pngData() else { return nil }
resizingImage = resizedImage
imageSizeKB = Double(imageData.count) / megaByte // ! Or devide for 1024 if you need KB but not kB
}
return resizingImage
}
}
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