Question

有没有办法可以改变NSimage或NSBitmapImageRep / CGimage等的颜色空间。我对任何方式持开放态度。最好是photoshop的方式。

Answer 1

CGImageRef CGImageCreateCopyWithColorSpace (
   CGImageRef image,
   CGColorSpaceRef colorspace
);

要获得CGColorSpaceRef，您可以执行

之类的操作

CGColorSpaceRef CGColorSpaceCreateDeviceRGB();

或参见this page了解如何创建其他颜色空间。

Answer 2

您在下面看到的代码存在问题

CGImageRef CGImageCreateCopyWithColorSpace (
CGImageRef image,
CGColorSpaceRef colorspace
);

不起作用，因为Quartz2D不支持CMYK图像或灰度图像的alpha，只有RGB图像支持它。您应该做的是创建2个图像然后组合，然后在CMYK颜色空间和图像与alpha。我已经搜索了很多关于这个主题的内容并最终找到了。可能是这个问题的作者不再需要它，但其他人可能需要它。

制作新的NSBitmapImageRep

let imageRep = NSBitmapImageRep(bitmapDataPlanes: nil,
                                      pixelsWide: Int(round(imageSize.width)),
                                      pixelsHigh: Int(round(imageSize.height)),
                                   bitsPerSample: 8,
                                 samplesPerPixel: 4,
                                        hasAlpha: false,
                                        isPlanar: false,
                                  colorSpaceName: NSDeviceCMYKColorSpace,
                                    bitmapFormat: NSBitmapFormat(rawValue: 0),
                                     bytesPerRow: Int(round(imageSize.width) * CGFloat(4)),
                                    bitsPerPixel: 0)

您需要将图像绘制到新的位图中假设你有colorSpace: NSColorSpace

let context = NSGraphicsContext(bitmapImageRep: imageRep)
NSGraphicsContext.saveGraphicsState()
NSGraphicsContext.setCurrentContext(context)
imageRep.setProperty(NSImageColorSyncProfileData, withValue: colorSpace.ICCProfileData)
// Do your drawing here
NSGraphicsContext.restoreGraphicsState()

在此之后，您将拥有一个imageRep，它是具有正确色彩空间但没有alpha（透明度）的图像。

您需要一个遮罩位图。获得面具很棘手。

let imageRep = NSBitmapImageRep(bitmapDataPlanes: nil,
                                      pixelsWide: Int(round(imageSize.width)),
                                      pixelsHigh: Int(round(imageSize.height)),
                                   bitsPerSample: 8,
                                 samplesPerPixel: 1,
                                        hasAlpha: false,
                                        isPlanar: false,
                                  colorSpaceName: NSDeviceWhiteColorSpace,
                                    bitmapFormat: NSBitmapFormat(rawValue: 0),
                                     bytesPerRow: Int(round(imageSize.width)),
                                    bitsPerPixel: 0)

将白色图像剪切为具有透明度的图像

if let graphicsPort = NSGraphicsContext.currentContext()?.graphicsPort {
    let context = unsafeBitCast(graphicsPort, CGContextRef.self)
    let imgRect = NSRect(origin: NSPoint.zero, size: image.extent.size)
    let ciContext = CIContext()
    let cgImage = ciContext.createCGImage(image, fromRect: image.extent)
    CGContextClipToMask(context, imgRect, cgImage)
}

将所有像素着色为白色，这将被裁剪为图像。

let context = NSGraphicsContext(bitmapImageRep: imageRep)
NSGraphicsContext.saveGraphicsState()
NSGraphicsContext.setCurrentContext(context)
imageRep.setProperty(NSImageColorSyncProfileData, withValue: colorSpace.ICCProfileData)
NSColor.whiteColor().setFill()
NSBezierPath.fillRect(NSRect(origin: NSPoint.zero, size: imageSize))
NSGraphicsContext.restoreGraphicsState()

在此步骤中，您有一个图像和一个遮罩。接下来我们需要结合它们。我正在使用这个小算法（您需要验证掩码和源图像具有相同的大小和相同的colorSpaceModel）：

func createCMYKAImageRepByApplingAlphaMask(srcImageRep: NSBitmapImageRep, alphaMaskImageRep alphaMask: NSBitmapImageRep) -> NSBitmapImageRep? {
    if canApplyMaskRepOnImageRep(srcImageRep, maskRep: alphaMask) == false {
        return nil
    }
    let alphaData = alphaMask.bitmapData
    let srcData = srcImageRep.bitmapData
    if let imageWithAlphaMaskRep = createEmptyCMYKABitmapImageRep(alphaMask.size) {
        if let colorSpaceData = imageColorSpace?.ICCProfileData {
             imageWithAlphaMaskRep.setProperty(NSImageColorSyncProfileData, withValue: colorSpaceData)
        }
        fillPixelsWithComponentsData(imageWithAlphaMaskRep, components: { (pixelIdx: Int) -> (UInt8, UInt8, UInt8, UInt8, UInt8) in
            let cyan = srcData[pixelIdx * 4 + 0]
            let magenta = srcData[pixelIdx * 4 + 1]
            let yellow = srcData[pixelIdx * 4 + 2]
            let black = srcData[pixelIdx * 4 + 3]
            let alpha = alphaData[pixelIdx]
            return (cyan, magenta, yellow, black, alpha)
        })
        return imageWithAlphaMaskRep
    }
    return nil
}

func createEmptyBitmapImageRep() -> NSBitmapImageRep? {
    let imageRep = NSBitmapImageRep(bitmapDataPlanes: nil,
                                          pixelsWide: Int(round(imageSize.width)),
                                          pixelsHigh: Int(round(imageSize.height)),
                                       bitsPerSample: 8,
                                     samplesPerPixel: 5,
                                            hasAlpha: true,
                                            isPlanar: false,
                                      colorSpaceName: NSDeviceCMYKColorSpace,
                                        bitmapFormat: NSBitmapFormat(rawValue: 0),
                                         bytesPerRow: Int(round(imageSize.width) * CGFloat(5)),
                                        bitsPerPixel: 0)
    return imageRep
}

private func fillPixelsWithComponentsData(imgRep: NSBitmapImageRep,
components: (Int) -> (cyan:UInt8, magenta:UInt8, yellow:UInt8, black:UInt8, alpha:UInt8)) {
    let imageRawData = imgRep.bitmapData
    let imageWidth = Int(imgRep.size.width)
    let imageHeight = Int(imgRep.size.height)
    for pixelIdx in 0 ..< (imageWidth * imageHeight) {
        let (cyan, magenta, yellow, black, alpha) = components(pixelIdx)
        let fAlpha = Float(alpha) / 255
        imageRawData[pixelIdx * 5 + 0] = UInt8(Float(cyan) * fAlpha)
        imageRawData[pixelIdx * 5 + 1] = UInt8(Float(magenta) * fAlpha)
        imageRawData[pixelIdx * 5 + 2] = UInt8(Float(yellow) * fAlpha)
        imageRawData[pixelIdx * 5 + 3] = UInt8(Float(black) * fAlpha)
        imageRawData[pixelIdx * 5 + 4] = alpha
    }
}

改变NSImage的色彩空间

2 个答案: