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Add MJPEG streaming support #185

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Add MJPEG streaming support #185

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118 changes: 118 additions & 0 deletions Source/Request+AlamofireImage.swift
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Original file line number Diff line number Diff line change
Expand Up @@ -35,6 +35,7 @@ import Cocoa
#endif

extension DataRequest {
static let JFIFMagicNumberStartOfImage = Data(bytes: [255, 216]) // 0xffd8
static var acceptableImageContentTypes: Set<String> = [
"image/tiff",
"image/jpeg",
Expand Down Expand Up @@ -97,6 +98,39 @@ extension DataRequest {
}
}

/// Creates an image initialized from the data using the specified mage options.
///
/// - parameter imageScale: The scale factor used when interpreting the image data to construct
/// `responseImage`. Specifying a scale factor of 1.0 results in an image whose
/// size matches the pixel-based dimensions of the image. Applying a different
/// scale factor changes the size of the image as reported by the size property.
/// `Screen.scale` by default.
/// - parameter inflateResponseImage: Whether to automatically inflate response image data for compressed formats
/// (such as PNG or JPEG). Enabling this can significantly improve drawing
/// performance as it allows a bitmap representation to be constructed in the
/// background rather than on the main thread. `true` by default.
///
/// - returns: An image.
public class func imageSerializer(
data: Data,
imageScale: CGFloat = DataRequest.imageScale,
inflateResponseImage: Bool = true)
-> UIImage?
{
guard data.count > 0 else {
return nil
}

do {
let image = try DataRequest.image(from: data, withImageScale: imageScale)
if inflateResponseImage { image.af_inflate() }

return image
} catch {
return nil
}
}

/// Adds a handler to be called once the request has finished.
///
/// - parameter imageScale: The scale factor used when interpreting the image data to construct
Expand Down Expand Up @@ -132,6 +166,46 @@ extension DataRequest {
)
}

/// Adds a handler to be called when the request has new image.
///
/// - parameter imageScale: The scale factor used when interpreting the image data to construct
/// `responseImage`. Specifying a scale factor of 1.0 results in an image whose
/// size matches the pixel-based dimensions of the image. Applying a different
/// scale factor changes the size of the image as reported by the size property.
/// This is set to the value of scale of the main screen by default, which
/// automatically scales images for retina displays, for instance.
/// `Screen.scale` by default.
/// - parameter inflateResponseImage: Whether to automatically inflate response image data for compressed formats
/// (such as PNG or JPEG). Enabling this can significantly improve drawing
/// performance as it allows a bitmap representation to be constructed in the
/// background rather than on the main thread. `true` by default.
/// - parameter completionHandler: A closure to be executed when the request has new image. The closure takes 1
/// argument: the image, if one could be created from the URL response and data.
///
/// - returns: The request.
@discardableResult
public func streamImage(
imageScale: CGFloat = DataRequest.imageScale,
inflateResponseImage: Bool = true,
completionHandler: @escaping (Image) -> Void)
-> Self
{
var imageData = Data()

return stream(closure: { (chunkData) in
if chunkData.starts(with: DataRequest.JFIFMagicNumberStartOfImage) {
if let image = DataRequest.imageSerializer(data: imageData,
imageScale: imageScale,
inflateResponseImage: inflateResponseImage) {
completionHandler(image)
}
imageData = Data()
}

imageData.append(chunkData)
})
}

private class func image(from data: Data, withImageScale imageScale: CGFloat) throws -> UIImage {
if let image = UIImage.af_threadSafeImage(with: data, scale: imageScale) {
return image
Expand Down Expand Up @@ -178,6 +252,28 @@ extension DataRequest {
}
}

/// Creates an image initialized from the data.
///
/// - returns: An image response serializer.
public class func imageSerializer(data: Data) -> NSImage? {
guard let validData = data, validData.count > 0 else {
return nil
}

guard Request.validateContentType(for: request, response: response) else {
return .failure(Request.contentTypeValidationError())
}

guard let bitmapImage = NSBitmapImageRep(data: validData) else {
return .failure(Request.imageDataError())
}

let image = NSImage(size: NSSize(width: bitmapImage.pixelsWide, height: bitmapImage.pixelsHigh))
image.addRepresentation(bitmapImage)

return image
}

/// Adds a handler to be called once the request has finished.
///
/// - parameter completionHandler: A closure to be executed once the request has finished. The closure takes 4
Expand All @@ -194,6 +290,28 @@ extension DataRequest {
)
}

/// Adds a handler to be called when the request has new image.
///
/// - parameter completionHandler: A closure to be executed when the request has new image. The closure takes 1
/// argument: the image, if one could be created from the URL response and data.
///
/// - returns: The request.
@discardableResult
public func streamImage(completionHandler: @escaping (Image) -> Void) -> Self {
var imageData = Data()

return stream(closure: { (chunkData) in
if chunkData.starts(with: Request.JFIFMagicNumberStartOfImage) {
if let image = Request.imageSerializer(data: imageData) {
completionHandler(image)
}
imageData = Data()
}

imageData.append(chunkData)
})
}

#endif

// MARK: - Private - Shared Helper Methods
Expand Down