UIIMAGEJPGRESTENTATION加倍图像分辨率

Question

我正在尝试将来自iPhone摄像机的图像保存到文件。我使用以下代码：

try UIImageJPEGRepresentation(toWrite, 0.8)?.write(to: tempURL, options: NSData.WritingOptions.atomicWrite)

这导致文件将towrite uiimage的分辨率加倍。我在手表的表达中确认，从uiimagejpegresentation创建新的UIImage使其分辨率翻了一番

-> toWrite.size CGSize  (width = 3264, height = 2448)   
-> UIImage(data: UIImageJPEGRepresentation(toWrite, 0.8)).size  CGSize? (width = 6528, height = 4896)

知道为什么会发生这种情况以及如何避免这种情况？

谢谢

Answer 1

您的初始图像具有比例因子= 2，但是当您从数据启动图像时，您将获得比例因子= 1的图像具有比例属性的图像：

@available(iOS 6.0, *)
public init?(data: Data, scale: CGFloat)

代表您可以设置比例尺

的游乐场代码

extension UIImage {
    class func with(color: UIColor, size: CGSize) -> UIImage? {
        let rect = CGRect(origin: .zero, size: size)
        UIGraphicsBeginImageContextWithOptions(size, true, 2.0)
        guard let context = UIGraphicsGetCurrentContext() else { return nil }
        context.setFillColor(color.cgColor)
        context.fill(rect)
        let image = UIGraphicsGetImageFromCurrentImageContext()
        UIGraphicsEndImageContext()
        return image
    }
}
let image = UIImage.with(color: UIColor.orange, size: CGSize(width: 100, height: 100))
if let image = image {
    let scale = image.scale
    if let data = UIImageJPEGRepresentation(image, 0.8) {
        if let newImage = UIImage(data: data, scale: scale) {
            debugPrint(newImage?.size)
        }
    }
}