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#if os(iOS)
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import UIKit
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#elseif os(macOS)
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import AppKit
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#endif
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private struct ImageHeaderData {
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static let png: UInt8 = 0x89
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static let jpeg: UInt8 = 0xFF
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static let gif: UInt8 = 0x47
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static let tiff_01: UInt8 = 0x49
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static let tiff_02: UInt8 = 0x4D
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}
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enum ImageFormat {
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case png
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case jpeg
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case gif
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case tiff
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}
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extension Data {
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var imageFormat: ImageFormat? {
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let buffer = self.first
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if buffer == ImageHeaderData.png {
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return .png
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} else if buffer == ImageHeaderData.jpeg {
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return .jpeg
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} else if buffer == ImageHeaderData.gif {
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return .gif
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} else if buffer == ImageHeaderData.tiff_01 || buffer == ImageHeaderData.tiff_02 {
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return .tiff
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} else {
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return nil
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}
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}
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}
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public protocol ImageDataConverter {
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/// Converts the image `data` to another format and returns the resulting Data.
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func convert(_ data: Data) -> Data
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}
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public extension ImageDataConverter {
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#if os(macOS)
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func jpegData(from image: NSImage) -> Data? {
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guard let cgImage = image.cgImage(forProposedRect: nil, context: nil, hints: nil) else { return nil }
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let bitmapRep = NSBitmapImageRep(cgImage: cgImage)
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return bitmapRep.representation(using: .jpeg, properties: [:])
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}
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#endif
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}
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extension Collection where Element == ImageDataConverter {
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/// Applies all converters to the provided `data` sequentially and returns the result.
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func convert(_ data: Data) -> Data {
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var result = data
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for converter in self {
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result = converter.convert(result)
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}
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return result
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}
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}
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/// An `ImageDataConverter` that converts image formats which are not supported by devRant to jpeg.
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/// Data of supported formats is just returned without any conversion.
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/// If the conversion fails, the original Data is returned.
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public struct UnsupportedToJpegImageDataConverter: ImageDataConverter {
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public func convert(_ data: Data) -> Data {
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switch data.imageFormat {
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case nil: // Format not recognized so it's probably not supported by devRant.
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#if os(iOS)
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return UIImage(data: data)?.jpegData(compressionQuality: 1) ?? data
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#elseif os(macOS)
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return NSImage(data: data).flatMap(jpegData) ?? data
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#else
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return data // This converter doesn't support platforms other than iOS and macOS. If you need to support other platforms, you can implement and use an own converter.
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#endif
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default: // Supported format recognized. No conversion needed.
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return data
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}
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}
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}
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public extension ImageDataConverter where Self == UnsupportedToJpegImageDataConverter {
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static var unsupportedToJpeg: Self { Self() }
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}
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