Question

我正在构建一个图像管理器类来处理UIImages的大小调整，裁剪等问题。我正在使用CGContext，因为它的速度可与UIGraphicsContext相媲美，其中JPEG来自http://nshipster.com/image-resizing/所见的基准。

这是我的经理班：

func resizeImage(exportedWidth width: Int, exportedHeight height: Int, originalImage image: UIImage) -> UIImage? {
    let cgImage = image.CGImage

    let width = width
    let height = height
    let bitsPerComponent = CGImageGetBitsPerComponent(cgImage)
    let bytesPerRow = CGImageGetBytesPerRow(cgImage)
    let colorSpace = CGImageGetColorSpace(cgImage)
    let bitmapInfo = CGImageGetBitmapInfo(cgImage)

    let context = CGBitmapContextCreate(nil, width, height, bitsPerComponent, bytesPerRow, colorSpace, bitmapInfo.rawValue)

    CGContextSetInterpolationQuality(context, .High)

    CGContextDrawImage(context, CGRect(origin: CGPointZero, size: CGSize(width: CGFloat(width), height: CGFloat(height))), cgImage)

    let scaledImage = CGBitmapContextCreateImage(context).flatMap { UIImage(CGImage: $0) }

    return scaledImage
}

没有什么真的太疯狂，但是当我将它添加到子类UITextView时我遇到了麻烦。我已经尝试将图像大小加倍然后用UIImageView压缩它无济于事。此代码正确显示正确的大小，但看起来像我的iPhone SE上的图像像素与屏幕像素比为1：1而不是理想的2：1视网膜屏幕。

func imagePickerController(picker: UIImagePickerController, didFinishPickingMediaWithInfo info: [String : AnyObject]) {
    if let pickedImage = info[UIImagePickerControllerOriginalImage] as? UIImage {
        let textViewWidth: CGFloat = self.view.frame.size.width - 130
        let percentResize = textViewWidth / pickedImage.size.width
        let toBeExportedHeight = pickedImage.size.height * percentResize
        let resizedImage = ImageManipulationManager.sharedInstance.resizeImage(exportedWidth: Int(textViewWidth),exportedHeight: Int(toBeExportedHeight), originalImage: pickedImage)

        let attachment = NSTextAttachment()
        attachment.image = resizedImage
        let attString = NSAttributedString(attachment: attachment)
        textView.textStorage.insertAttributedString(attString, atIndex: textView.selectedRange.location)
        textInputbar.layoutIfNeeded()
        textView.becomeFirstResponder()
        print(textView.text.characters.count)
    }
    dismissViewControllerAnimated(true, completion: nil)
}

Answer 1

双分辨率屏幕的图像需要是双分辨率的。这意味着它应该是您想要的实际大小的两倍宽和两倍高，当您从CGImage派生它时，UIImage附加scale 2。

使用CGContext调整UIImage的大小使我的图像变得柔和，像素密度错误

1 个答案: