如何调整UIImage大小以减少上传图像大小
如何调整UIImage大小以减少上传图像大小
提问于 2015-03-19 05:00:02
我一直在搜索谷歌，只遇到一些库，这些库要么降低了高度/宽度，要么通过CoreImage编辑了CoreImage外观。但我没有看到或找到一个库，这篇文章解释了如何缩小图像大小，所以当它上传时，并不是完整的图像大小。
到目前为止我有这样的想法：
if image != nil {
//let data = NSData(data: UIImagePNGRepresentation(image))
let data = UIImagePNGRepresentation(image)
body.appendString("--\(boundary)\r\n")
body.appendString("Content-Disposition: form-data; name=\"image\"; filename=\"randomName\"\r\n")
body.appendString("Content-Type: image/png\r\n\r\n")
body.appendData(data)
body.appendString("\r\n")
}它正在发送12 it的照片。我怎样才能把这个减少到1mb呢？谢谢!
回答 20
Stack Overflow用户
回答已采纳
发布于 2020-08-29 11:00:15
Swift 5& Xcode 14
我对这里的解决方案不满意，这些解决方案根据给定的KB大小生成图像，因为大多数解决方案都使用.jpegData(compressionQuality: x)。此方法不适用于大型图像，因为即使将压缩质量设置为0.0，大图像仍将保持较大，例如，由较新的iPhone的纵向模式产生的10 MB仍然在1MB以上，而compressionQuality设置为0.0。
因此，我在这里使用了一些答案，并重写了一个Helper Struct，该结构转换背景que中的图像：
import UIKit
struct ImageCompressor {
static func compress(image: UIImage, maxByte: Int,
completion: @escaping (UIImage?) -> ()) {
DispatchQueue.global(qos: .userInitiated).async {
guard let currentImageSize = image.jpegData(compressionQuality: 1.0)?.count else {
return completion(nil)
}
var iterationImage: UIImage? = image
var iterationImageSize = currentImageSize
var iterationCompression: CGFloat = 1.0
while iterationImageSize > maxByte && iterationCompression > 0.01 {
let percantageDecrease = getPercantageToDecreaseTo(forDataCount: iterationImageSize)
let canvasSize = CGSize(width: image.size.width * iterationCompression,
height: image.size.height * iterationCompression)
UIGraphicsBeginImageContextWithOptions(canvasSize, false, image.scale)
defer { UIGraphicsEndImageContext() }
image.draw(in: CGRect(origin: .zero, size: canvasSize))
iterationImage = UIGraphicsGetImageFromCurrentImageContext()
guard let newImageSize = iterationImage?.jpegData(compressionQuality: 1.0)?.count else {
return completion(nil)
}
iterationImageSize = newImageSize
iterationCompression -= percantageDecrease
}
completion(iterationImage)
}
}
private static func getPercantageToDecreaseTo(forDataCount dataCount: Int) -> CGFloat {
switch dataCount {
case 0..<3000000: return 0.05
case 3000000..<10000000: return 0.1
default: return 0.2
}
}
}将图像压缩到最大1MB：
ImageCompressor.compress(image: image, maxByte: 1000000) { image in
guard let compressedImage = image else { return }
// Use compressedImage
}
}Stack Overflow用户
发布于 2015-03-19 06:00:11
Xcode 9·Swift 4或更高版本的
编辑/更新:对于iOS10+，我们可以使用UIGraphicsImageRenderer。对于较旧的Swift语法，请检查编辑历史记录。
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 resized(toWidth width: CGFloat, isOpaque: Bool = true) -> UIImage? {
let canvas = CGSize(width: width, height: CGFloat(ceil(width/size.width * size.height)))
let format = imageRendererFormat
format.opaque = isOpaque
return UIGraphicsImageRenderer(size: canvas, format: format).image {
_ in draw(in: CGRect(origin: .zero, size: canvas))
}
}
}用法：
let image = UIImage(data: try! Data(contentsOf: URL(string:"http://i.stack.imgur.com/Xs4RX.jpg")!))!
let thumb1 = image.resized(withPercentage: 0.1)
let thumb2 = image.resized(toWidth: 72.0)Stack Overflow用户
发布于 2015-03-19 05:22:44
这就是我调整图像大小的方法。
-(UIImage *)resizeImage:(UIImage *)image
{
float actualHeight = image.size.height;
float actualWidth = image.size.width;
float maxHeight = 300.0;
float maxWidth = 400.0;
float imgRatio = actualWidth/actualHeight;
float maxRatio = maxWidth/maxHeight;
float compressionQuality = 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;
}
}
CGRect rect = CGRectMake(0.0, 0.0, actualWidth, actualHeight);
UIGraphicsBeginImageContext(rect.size);
[image drawInRect:rect];
UIImage *img = UIGraphicsGetImageFromCurrentImageContext();
NSData *imageData = UIImageJPEGRepresentation(img, compressionQuality);
UIGraphicsEndImageContext();
return [UIImage imageWithData:imageData];
}使用这种方法，我的图像有6.5MB，减少到104 KB。
Swift 4代码：
func resize(_ image: UIImage) -> UIImage {
var actualHeight = Float(image.size.height)
var actualWidth = 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 = CGRect(x: 0.0, y: 0.0, width: CGFloat(actualWidth), height: CGFloat(actualHeight))
UIGraphicsBeginImageContext(rect.size)
image.draw(in: rect)
let img = UIGraphicsGetImageFromCurrentImageContext()
let imageData = img?.jpegData(compressionQuality: CGFloat(compressionQuality))
UIGraphicsEndImageContext()
return UIImage(data: imageData!) ?? UIImage()
}页面原文内容由Stack Overflow提供。腾讯云小微IT领域专用引擎提供翻译支持
原文链接：
https://stackoverflow.com/questions/29137488
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