当我尝试混合两个图像时，表达式类型不明确，没有更多上下文错误消息

Question

我正在尝试使用下面的代码混合两个相同大小的图像，但是 "filteredImage.image?.draw(in: areaSize, blendMode: .normal, alpha: opa)" 此代码将显示错误消息 "Type of expression is ambiguous without more context".. 有什么问题吗？

        let originalWidth:CGFloat  = originalImageView.frame.size.width
        let originalHeight:CGFloat = originalImageView.frame.size.height
        var opa = intensity * 0.01

        let size = CGSize(width: originalWidth, height: originalHeight)

        UIGraphicsBeginImageContext(size)

        let areaSize = CGRect(x: 0, y: 0, width: size.width, height: size.height)
        let blendImageSize = areaSize

        originalImageView.image?.draw(in: areaSize, blendMode: .normal, alpha: 1.0)

        filteredImageView.image?.draw(in: areaSize, blendMode: .normal, alpha: opa)

        originalImageView.image = UIGraphicsGetImageFromCurrentImageContext()

        UIGraphicsEndImageContext()

Answer 1

改变

alpha: opa

至

alpha: CGFloat(opa)

当我尝试混合两个图像时，表达式类型不明确，没有更多上下文错误消息

Type of expression is ambiguous without more context error message when I try to blend two images

swift

swift4

cgrect

blend-mode