inabox/InABox.Avalonia.Platform.iOS/PDFRenderer.iOS.cs

using InABox.Core; 

namespace InABox.Avalonia.Platform.iOS;

public class iOS_PdfRenderer : IPdfRenderer
{

    public Logger? Logger { get; set; }

    public byte[]? PdfToImage(byte[]? pdf, int pageIndex, int dpi)
    {

        float scale = 2F;

        // Step 1: Load the PDF document from byte array
        using var data = NSData.FromArray(pdf);
        using var provider = new CGDataProvider(data);
        using var pdfDoc = new CGPDFDocument(provider);

        // Validate page index
        int pageCount = (int)pdfDoc.Pages;
        if (pageIndex < 0 || pageIndex >= pageCount)
            throw new ArgumentOutOfRangeException(nameof(pageIndex), "Invalid PDF page index.");

        using var page = pdfDoc.GetPage(pageIndex + 1); // Pages are 1-indexed
        var pageRect = page.GetBoxRect(CGPDFBox.Media);
        var scaledSize = new CGSize(pageRect.Width * scale, pageRect.Height * scale);

        // Step 2: Render the page to an image
        UIGraphics.BeginImageContextWithOptions(scaledSize, false, 1.0f);
        using (var context = UIGraphics.GetCurrentContext())
        {
            context.SaveState();
            context.TranslateCTM(0, scaledSize.Height);
            context.ScaleCTM(scale, -scale); // Flip and scale
            context.DrawPDFPage(page);
            context.RestoreState();
        }

        using var image = UIGraphics.GetImageFromCurrentImageContext();
        UIGraphics.EndImageContext();

        // Step 3: Convert UIImage to PNG byte array
        using var pngData = image.AsPNG();
        return pngData.ToArray();

    }

    public Task<byte[]?> PdfToImageAsync(byte[]? pdf, int page, int dpi)
    {

        var tcs = new TaskCompletionSource<byte[]>();

        UIApplication.SharedApplication.BeginInvokeOnMainThread(() =>
        {
            try
            {
                var result = PdfToImage(pdf, page, dpi);
                tcs.SetResult(result);
            }
            catch (Exception ex)
            {
                tcs.SetException(ex);
            }
        });

        return tcs.Task;


    }

    public byte[]? ImageToPdf(byte[]? image)
    {
        return null;
    }

    public Task<byte[]?> ImageToPdfAsync(byte[]? image)
    {
        var tcs = new TaskCompletionSource<byte[]>();

        UIApplication.SharedApplication.BeginInvokeOnMainThread(() =>
        {
            try
            {
                var result = ImageToPdf(image);
                tcs.SetResult(result);
            }
            catch (Exception ex)
            {
                tcs.SetException(ex);
            }
        });

        return tcs.Task;
    }


}