MacOS SwiftUI中创建NSImage并显示的两类技术问题求助

环境信息 #

• Xcode 15.2
• Mac mini M1 64位
• macOS Sonoma 14.6.1

此前已实现通过C++视频回调函数向macOS的SwiftUI视图传递帧计数并显示，现尝试传递RGB原始数据及数据大小以显示图像，但遇到以下问题：

相关代码 #

1. MyCLibrary.h #

typedef void callback_t1(uint8_t* rgbBufferPtr, uint32_t rgbBufferBytes);
callback_t1* callback1 = NULL;

2. CWrapperBridging.h #

void setCallBack1(callback_t1 _callback1);

3. CWrapper.cpp #

std::vector<uint8_t> vctFrameData;

extern "C" void setCallBack1(callback_t1 _callback1)
{
    callback1 = _callback1;
}

extern "C" void videoCallbackFunction(void* RGBbufferPtr, uint32_t RGBbufferBytes)
{
    int sz = (int)vctFrameData.size();

    if(sz != (int)RGBbufferBytes)
    {
        vctFrameData.resize(RGBbufferBytes);
        std::cout << "*** vctFrameData is resized @ videoCallbackFunction()" << std::endl;
    }

    std::memcpy(&vctFrameData[0], RGBbufferPtr, RGBbufferBytes);

    uint8_t* buffer_ptr = &vctFrameData[0]; 

    if(callback1)
        callback1(buffer_ptr, RGBbufferBytes);
}

4. MyCLibraryInterface.swift #

import Foundation
import AppKit

class MyCLibraryInterface: ObservableObject {
    @Published var nsimage: NSImage
    
    static let shared = MyCLibraryInterface()
    
    init() {
        setCallBack1 { 
            let newNsImage = ??? // 不知道怎么创建NSImage
            
            DispatchQueue.main.async {
                MyCLibraryInterface.shared.nsimage = newNsImage as NSImage
            }
        }
    }
}

5. ContentView.swift #

import SwiftUI

struct ContentView: View {
    @ObservedObject var myCLibInterface: MyCLibraryInterface = MyCLibraryInterface.shared
        
    var body: some View {
        
        VStack {
            Image(myCLibInterface.nsimage) // 报错：<Missing argument label 'nsImage:' in call>，怎么解决？
                .frame(width: 640.0, height: 480.0)
        }
        .padding()
    }
 }

#Preview {
    ContentView()
}

具体问题 #

1. 在MyCLibraryInterface类的init方法中调用setCallBack1时，如何创建NSImage？
2. 使用Image(myCLibInterface.nsimage)时出现<Missing argument label 'nsImage:' in call>错误，该如何解决？

问题1：从RGB原始数据创建NSImage #

要从RGB缓冲区生成NSImage，需要先将原始数据封装为CGImage，再转换为NSImage。注意必须明确图像的宽、高、像素格式（比如是24位RGB还是32位RGBA），以下以常见的640×480分辨率、24位RGB格式为例（可根据实际视频参数调整）：

修改MyCLibraryInterface的回调代码：

init() {
    // 初始化默认占位图，避免nil报错
    self.nsimage = NSImage(size: CGSize(width: 640, height: 480))
    
    setCallBack1 { rgbBufferPtr, rgbBufferBytes in
        // 替换为实际视频帧的宽高和像素参数
        let width = 640
        let height = 480
        let bytesPerPixel = 3 // 24位RGB每个像素占3字节
        let bytesPerRow = width * bytesPerPixel
        
        // 校验缓冲区大小是否匹配
        guard rgbBufferBytes == width * height * bytesPerPixel else {
            print("RGB缓冲区大小与图像参数不匹配")
            return
        }
        
        // 将C指针数据转为Swift Data
        let data = Data(bytes: rgbBufferPtr, count: Int(rgbBufferBytes))
        guard let dataProvider = CGDataProvider(data: data as CFData) else {
            print("创建CGDataProvider失败")
            return
        }
        
        // 创建CGImage
        guard let cgImage = CGImage(
            width: width,
            height: height,
            bitsPerComponent: 8, // 每个颜色分量8位
            bitsPerPixel: bytesPerPixel * 8,
            bytesPerRow: bytesPerRow,
            space: CGColorSpaceCreateDeviceRGB(),
            bitmapInfo: CGBitmapInfo(rawValue: CGImageAlphaInfo.none.rawValue), // 无alpha通道
            provider: dataProvider,
            decode: nil,
            shouldInterpolate: true,
            intent: .defaultIntent
        ) else {
            print("创建CGImage失败")
            return
        }
        
        // 转换为NSImage
        let newNsImage = NSImage(cgImage: cgImage, size: CGSize(width: width, height: height))
        
        // 切换到主线程更新UI
        DispatchQueue.main.async {
            MyCLibraryInterface.shared.nsimage = newNsImage
        }
    }
}

补充：如果是32位RGBA格式，需将bytesPerPixel改为4，bitsPerPixel改为32，bitmapInfo改为CGImageAlphaInfo.premultipliedLast.rawValue。建议从C++端同时传递宽高参数，避免硬编码。

问题2：修复Image初始化的参数标签错误 #

SwiftUI的Image初始化器接收NSImage时，必须显式指定参数标签nsImage:，修改代码如下：

Image(nsImage: myCLibInterface.nsimage)
    .frame(width: 640.0, height: 480.0)

内容的提问来源于stack exchange，提问作者Wunian