到目前为止,我正在为iOS应用程序构建扫描仪组件,并且将结果图像裁剪为正确的角度。现在,我需要将彩色图像转换为黑白“扫描”文档。
我尝试使用-“ CIPhotoEffectNoir”,但它的灰度更高,然后完全是黑白。我希望获得100%黑色和100%白色的全对比度图像。
我该如何实现?谢谢
您可以使用CIColorControls并设置Contrast Key kCIInputContrastKey来增加黑白对比度,如下所示:
kCIInputContrastKey
Xcode 9•Swift 4
extension String { static let colorControls = "CIColorControls" }
extension UIImage { var coreImage: CIImage? { return CIImage(image: self) } }
extension CIImage { var uiImage: UIImage? { return UIImage(ciImage: self) } func applying(contrast value: NSNumber) -> CIImage? { return applyingFilter(.colorControls, parameters: [kCIInputContrastKey: value]) } func renderedImage() -> UIImage? { guard let image = uiImage else { return nil } return UIGraphicsImageRenderer(size: image.size, format: image.imageRendererFormat).image { _ in image.draw(in: CGRect(origin: .zero, size: image.size)) } } }
let url = URL(string: "https://i.stack.imgur.com/Xs4RX.jpg")! do { if let coreImage = UIImage(data: try Data(contentsOf: url))?.coreImage, let increasedContrast = coreImage.applying(contrast: 1.5) { imageView.image = increasedContrast.uiImage // if you need to convert your image to data (JPEG/PNG) you would need to render the ciimage using renderedImage method on CIImage } } catch { print(error) }
要将颜色转换为灰度,可以将饱和度键kCIInputSaturationKey设置为零:
kCIInputSaturationKey
extension CIImage { func applying(saturation value: NSNumber) -> CIImage? { return applyingFilter(.colorControls, parameters: [kCIInputSaturationKey: value]) } var grayscale: CIImage? { return applying(saturation: 0) } }
let url = URL(string: "https://i.stack.imgur.com/Xs4RX.jpg")! do { if let coreImage = UIImage(data: try Data(contentsOf: url))?.coreImage, let grayscale = coreImage.grayscale { // use grayscale image here imageView.image = grayscale.uiImage } } catch { print(error) }