iOS中如何将CVPixelBuffer格式的灰度深度图转换为JPEG/PNG并保存？

我之前也碰到过一模一样的问题！能把深度图渲染到屏幕却存不了本地文件，核心原因是得把CVPixelBuffer里的灰度深度数据转换成可编码的图像格式，下面给你两种亲测有效的解决方法：

方法一：转成UIImage再保存（简单易上手） #

先把CVPixelBuffer转换成UIImage，再利用UIImage自带的方法保存成JPEG/PNG，代码逻辑很直观：

import UIKit
import CoreImage

// 将CVPixelBuffer转为UIImage
func pixelBufferToUIImage(_ pixelBuffer: CVPixelBuffer) -> UIImage? {
    let ciImage = CIImage(cvPixelBuffer: pixelBuffer)
    // 用硬件加速的CIContext提升转换效率
    let context = CIContext(options: [.useSoftwareRenderer: false])
    guard let cgImage = context.createCGImage(ciImage, from: ciImage.extent) else {
        return nil
    }
    return UIImage(cgImage: cgImage)
}

// 保存UIImage到本地
if let depthImage = pixelBufferToUIImage(yourDepthPixelBuffer) {
    // 保存为JPEG（压缩质量0.8，可调整）
    if let jpegData = depthImage.jpegData(compressionQuality: 0.8) {
        let saveURL = FileManager.default.urls(for: .documentDirectory, in: .userDomainMask)[0]
            .appendingPathComponent("depth_map.jpg")
        try? jpegData.write(to: saveURL)
    }
    
    // 保存为PNG（无损，适合保留精确深度值）
    if let pngData = depthImage.pngData() {
        let saveURL = FileManager.default.urls(for: .documentDirectory, in: .userDomainMask)[0]
            .appendingPathComponent("depth_map.png")
        try? pngData.write(to: saveURL)
    }
}

如果你的CVPixelBuffer是16位灰度格式（比如kCVPixelFormatType_OneComponent16），记得在转换时指定对应的颜色空间和位图信息，避免出现颜色失真。

方法二：用ImageIO直接编码（高效适合大尺寸） #

如果深度图尺寸较大，直接用ImageIO编码CVPixelBuffer会更高效，跳过UIImage的中间转换步骤：

import UIKit
import ImageIO
import MobileCoreServices

// 直接将CVPixelBuffer保存为图像文件
func saveDepthPixelBuffer(_ pixelBuffer: CVPixelBuffer, to url: URL, isPNG: Bool) throws {
    // 锁定像素缓冲区的内存地址
    CVPixelBufferLockBaseAddress(pixelBuffer, .readOnly)
    defer { CVPixelBufferUnlockBaseAddress(pixelBuffer, .readOnly) }
    
    let width = CVPixelBufferGetWidth(pixelBuffer)
    let height = CVPixelBufferGetHeight(pixelBuffer)
    let bytesPerRow = CVPixelBufferGetBytesPerRow(pixelBuffer)
    let baseAddress = CVPixelBufferGetBaseAddress(pixelBuffer)
    
    // 创建灰度颜色空间
    let colorSpace = CGColorSpaceCreateDeviceGray()
    // 根据像素格式设置位图信息（这里以8位灰度为例）
    let bitmapInfo = CGBitmapInfo(rawValue: CGImageAlphaInfo.none.rawValue)
    
    // 创建CGContext
    guard let context = CGContext(data: baseAddress,
                                  width: width,
                                  height: height,
                                  bitsPerComponent: 8,
                                  bytesPerRow: bytesPerRow,
                                  space: colorSpace,
                                  bitmapInfo: bitmapInfo.rawValue) else {
        throw NSError(domain: "DepthSaveError", code: 0, userInfo: [NSLocalizedDescriptionKey: "无法创建CGContext"])
    }
    
    // 生成CGImage
    guard let cgImage = context.makeImage() else {
        throw NSError(domain: "DepthSaveError", code: 1, userInfo: [NSLocalizedDescriptionKey: "无法生成CGImage"])
    }
    
    // 创建图像编码目标
    let imageType = isPNG ? kUTTypePNG : kUTTypeJPEG
    guard let destination = CGImageDestinationCreateWithURL(url as CFURL, imageType, 1, nil) else {
        throw NSError(domain: "DepthSaveError", code: 2, userInfo: [NSLocalizedDescriptionKey: "无法创建编码目标"])
    }
    
    // 如果是JPEG，可以添加压缩质量参数
    let properties = isPNG ? nil : [kCGImageDestinationLossyCompressionQuality as String: 0.8] as CFDictionary
    CGImageDestinationAddImage(destination, cgImage, properties)
    
    // 完成编码
    guard CGImageDestinationFinalize(destination) else {
        throw NSError(domain: "DepthSaveError", code: 3, userInfo: [NSLocalizedDescriptionKey: "编码图像失败"])
    }
}

// 调用示例
let saveURL = FileManager.default.urls(for: .documentDirectory, in: .userDomainMask)[0]
    .appendingPathComponent("depth_map.png")
try? saveDepthPixelBuffer(yourDepthPixelBuffer, to: saveURL, isPNG: true)

额外注意事项 #

• 确保你的CVPixelBuffer格式是标准灰度格式（比如kCVPixelFormatType_OneComponent8或kCVPixelFormatType_OneComponent16），否则需要先做格式转换。
• 若要保留精确的深度数据，优先选择PNG格式保存；如果追求文件体积小，再选JPEG。

内容的提问来源于stack exchange，提问作者NoOneHere