iOS CGContext渲染颜色

1、从上下文获取CIImage

        guard let originCGImage = UIGraphicsGetImageFromCurrentImageContext()?.cgImage else { return }
        UIGraphicsEndImageContext()
        let originCIImage = CIImage(cgImage: originCGImage)

2、给CIImage增加滤镜

        guard let pinkMonochromeFilter = CIFilter(name: "CIColorMonochrome") else { return }
        pinkMonochromeFilter.setDefaults()
        pinkMonochromeFilter.setValue(originCIImage, forKey: kCIInputImageKey)
        let pinkColor = CIColor(color: kltuiColor(withHex: 0xFF7538))
        pinkMonochromeFilter.setValue(pinkColor, forKey: "inputColor")
        pinkMonochromeFilter.setValue(1.0, forKey: "inputIntensity")

3、把加滤镜后的CIImage转成CGImage

        let pinkCIImage = pinkMonochromeFilter.outputImage
        let pinkCGImage = ciContext.createCGImage(pinkCIImage, from: pinkrect)

4、变换坐标轴，把CGImage绘制在CGContext上

            context.textMatrix = .identity
            context.translateBy(x: 0, y: totalHeight)
            context.scaleBy(x: 1.0, y: -1.0)

            context.draw(pinkCGImage!, in: pinkrect)

            context.translateBy(x: 0, y: totalHeight)
            context.scaleBy(x: 1.0, y: -1.0)