Gifu/Source/UIImageExtension.swift

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Swift
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/// A `UIImage` extension that makes it easier to resize the image and inspect its size.
extension UIImage {
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/// Resizes an image instance.
///
/// :param: size The new size of the image.
/// :returns: A new resized image instance.
func resize(size: CGSize) -> UIImage {
UIGraphicsBeginImageContextWithOptions(size, false, 0.0)
self.drawInRect(CGRect(origin: CGPointZero, size: size))
let newImage = UIGraphicsGetImageFromCurrentImageContext()
UIGraphicsEndImageContext()
return newImage
}
/// Resizes an image instance to fit inside a constraining size while keeping the aspect ratio.
///
/// :param: size The constraining size of the image.
/// :returns: A new resized image instance.
func resizeAspectFit(size: CGSize) -> UIImage {
let newSize = self.size.sizeConstrainedBySize(size)
return resize(newSize)
}
/// Resizes an image instance to fill a constraining size while keeping the aspect ratio.
///
/// :param: size The constraining size of the image.
/// :returns: A new resized image instance.
func resizeAspectFill(size: CGSize) -> UIImage {
let newSize = self.size.sizeFillingSize(size)
return resize(newSize)
}
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/// Returns a new `UIImage` instance using raw image data and a size.
///
/// :param: data Raw image data.
/// :param: size The size to be used to resize the new image instance.
/// :returns: A new image instance from the passed in data.
class func imageWithData(data: NSData, size: CGSize) -> UIImage? {
return UIImage(data: data)?.resize(size)
}
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/// Returns an image size from raw image data.
///
/// :param: data Raw image data.
/// :returns: The size of the image contained in the data.
class func sizeForImageData(data: NSData) -> CGSize? {
return UIImage(data: data)?.size
}
}
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private extension CGSize {
/// Calculates the aspect ratio of the size.
///
/// :returns: aspectRatio The aspect ratio of the size.
var aspectRatio: CGFloat {
if height == 0 { return 1 }
return width / height
}
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/// Finds a new size constrained by a size keeping the aspect ratio.
///
/// :param: size The contraining size.
/// :returns: size A new size that fits inside the contraining size with the same aspect ratio.
func sizeConstrainedBySize(size: CGSize) -> CGSize {
let aspectWidth = round(aspectRatio * size.height)
let aspectHeight = round(size.width / aspectRatio)
if aspectWidth > size.width {
return CGSize(width: size.width, height: aspectHeight)
} else {
return CGSize(width: aspectWidth, height: size.height)
}
}
/// Finds a new size filling the given size while keeping the aspect ratio.
///
/// :param: size The contraining size.
/// :returns: size A new size that fills the contraining size keeping the same aspect ratio.
func sizeFillingSize(size: CGSize) -> CGSize {
let aspectWidth = round(aspectRatio * size.height)
let aspectHeight = round(size.width / aspectRatio)
if aspectWidth > size.width {
return CGSize(width: aspectWidth, height: size.height)
} else {
return CGSize(width: size.width, height: aspectHeight)
}
}
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}