[英]How can I convert an UIImage to grayscale in Swift using CIFilter?
我正在为iOS应用程序构建扫描仪组件到目前为止,我已经裁剪了结果图像,并且正确的视角。 现在我需要将彩色图像变成黑白“扫描”文档。
我尝试使用 - “CIPhotoEffectNoir”,但它更灰度,然后完全黑白。 我希望获得100%黑色和100%白色的完整对比图像。
我怎样才能做到这一点? 谢谢
您可以使用CIColorControls并设置对比度键kCIInputContrastKey
来增加黑/白对比度,如下所示:
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:
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)
}
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