Ios 使用swift将图像转换为A4大小的pdf

我想将UIImage数组转换为pdf文件.PDF文件页面大小应为A4.我try 了PDFKIT，但结果不合适.

What I want:

1. A4页大小
2. 图像应居中并在页面上zoom (数组图像尺寸不相同)

What I tried:

    func makePDF(images: [UIImage])-> PDFDocument? {
    let pdfDoc = PDFDocument()
    
    for (index,image) in images.enumerated() {
        let resizedImage = resizeImage(image: image, targetSize: PDFPageSize.A4)
        guard let cgImage = resizedImage?.cgImage else { return pdfDoc }
        let uiimage = UIImage(cgImage: cgImage, scale: image.scale, orientation: .up)
        if let pdfPage = PDFPage(image: uiimage) {
            let page = CGRect(x: 0, y: 0, width: 595.2, height: 841.8) // A4, 72 dpi
            pdfPage.setBounds(page, for: PDFDisplayBox.mediaBox)
            pdfDoc.insert(pdfPage, at: index)
        }
        
    }
    return pdfDoc
}

func resizeImage(image: UIImage, targetSize: CGSize) -> UIImage? {
    let size = image.size
    let widthRatio  = targetSize.width  / size.width
    let heightRatio = targetSize.height / size.height
    var newSize: CGSize
    if(widthRatio > heightRatio) {
        newSize = CGSize(width: size.width * heightRatio, height: size.height * heightRatio)
    } else {
        newSize = CGSize(width: size.width * widthRatio, height: size.height * widthRatio)
    }
    let rect = CGRect(x: 0, y: 0, width: newSize.width, height: newSize.height)
    UIGraphicsBeginImageContextWithOptions(newSize, false, 1.0)
    image.draw(in: rect)
    let newImage = UIGraphicsGetImageFromCurrentImageContext()
    UIGraphicsEndImageContext()
    return newImage
}

My Output is:

1. 图像丢失
2. 图像裁剪
3. 不在中间位置

My Output

My Desire Output is:

My Desire Output

我该怎么做？