改變NSImage的色彩空間

Question

有沒有辦法改變NSimage或NSBitmapImageRep/CGimage之類的色彩空間。我對任何方式都是開放的。最好的方式photoshop做到這一點。

Answer 1

CGImageRef CGImageCreateCopyWithColorSpace (
    CGImageRef image, 
    CGColorSpaceRef colorspace 
); 

爲了得到一個CGColorSpaceRef，你可以做這樣的事情

CGColorSpaceRef CGColorSpaceCreateDeviceRGB(); 

或參閱this page對於如何創建其他顏色空間。

Answer 2

與你看到下面

CGImageRef CGImageCreateCopyWithColorSpace (
CGImageRef image, 
CGColorSpaceRef colorspace 
); 

的代碼的問題是行不通的，因爲Quartz2D不支持CMYK圖像或灰度圖像α，它僅由RGB圖像的支持。 你應該做的是創建2個圖像，然後結合CMYK色彩空間和圖像與阿爾法。我已經搜索了很多關於這個話題，並最終找到。可能是這個問題的作者不再需要它，但其他人可能需要它。

1. 創造新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) 
   

2. 您需要繪製圖像插入新的位圖 可以說你有colorSpace: NSColorSpace

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

3. 此之後，你將有一個imageRep那是具有正確色彩空間但沒有alpha（透明度）的圖像。

4. 您需要一個掩碼位圖。獲得面具是棘手的。

   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) 
   

5. 夾白圖像圖像與透明

   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) 
   } 
   

6. 彩色化以白色爲主色調的所有像素，這將是裁剪圖像。

   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() 
   

7. 在這一步你有一個圖像和一個面具。接下來我們需要將它們合併。我使用這個小算法（你需要驗證面具和源圖像具有相同的尺寸和相同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 
       } 
   }