puppeteerSharp failed to display image in pdf

[kirticism]

Hi, I am encountering an issue while converting HTML to PDF using PuppeteerSharp. Specifically, the images are not displaying in the generated PDF. Despite following various solutions suggested on StackOverflow, the problem persists. Below is the method I am using to perform the HTML to PDF conversion. I would appreciate any guidance or solutions you could provide.

public async Task HtmlToPdf(string htmlContent, string fileName) { var startTime = DateTimeOffset.UtcNow; _logger.LogInformation("Executing GeneratePdf: {fileName}...", fileName);

var launchOptions = new LaunchOptions { Headless = true };
await new BrowserFetcher().DownloadAsync(BrowserFetcher.DefaultChromiumRevision);
using (var browser = await Puppeteer.LaunchAsync(launchOptions))
using (var page = await browser.NewPageAsync())
{
    await page.SetContentAsync(htmlContent);

    await page.AddStyleTagAsync(new AddTagOptions { Content = "body { font-size: 20px; margin: 50px; }" });
    await page.WaitForSelectorAsync("img");
    var pdfBytes = await page.PdfDataAsync(new PdfOptions { Format = PaperFormat.A4 });

    var filePath = Path.Combine(Path.GetTempPath(), fileName);
    File.WriteAllBytes(filePath, pdfBytes);

    var formFile = await CreateFormFile(filePath, fileName);

    File.Delete(filePath);

    var endTime = DateTimeOffset.UtcNow;
    var executionTime = endTime - startTime;
    _logger.LogInformation("Time taken to execute GeneratePdf: {fileName}. Time: {ExecutionTime} ms",
                           fileName, executionTime.TotalMilliseconds);

    return formFile;
}

}

[mstijak]

await page.WaitForSelectorAsync("img");

This is not enough. You should wait until the image loads too.

Perhaps this will do the trick.

await page.WaitForNetworkIdleAsync();

[skalahonza]

I am facing the same issue

        var pdfOptions = new PdfOptions
        {
            PrintBackground = true, // otherwise background of tables won't be printed
            Format = request.Options.Format.ToPuppeteerPaperFormat(),
            Landscape = request.Options.PrintOrientation == PrintOrientation.Landscape,
            MarginOptions =
            {
                Bottom = $"{request.Options.MarginOptions.Bottom}mm",
                Left = $"{request.Options.MarginOptions.Left}mm",
                Right = $"{request.Options.MarginOptions.Right}mm",
                Top = $"{request.Options.MarginOptions.Top + (request.Options.HeaderHeight != 0 ? HeaderContentGap + request.Options.HeaderHeight : 0)}mm"
            },
            Scale = new decimal(request.PrintScale),
            HeaderTemplate = headerTemplate,
            FooterTemplate = "<div></div>", // we want empty footer
            DisplayHeaderFooter = !string.IsNullOrEmpty(headerTemplate)
        };        
        await using var stream = await contentPage.PdfStreamAsync(pdfOptions);

to my surprise the images are seen in the html right before the PDF generation

but this happens when the PDF is generated

I tried many methods for waiting

    private async Task WaitForPageToBeLoaded(IPage page, CancellationToken ct)
    {
        _logger.LogDebug("Waiting for all fonts to be loaded");
        ct.ThrowIfCancellationRequested();
        await page.EvaluateExpressionHandleAsync("document.fonts.ready");
        _logger.LogDebug("Page fonts loaded");

        _logger.LogDebug("Emulating Screen media type");
        ct.ThrowIfCancellationRequested();
        await page.EmulateMediaTypeAsync(MediaType.Screen);
        _logger.LogDebug("Screen media type emulated");

        await page.SetJavaScriptEnabledAsync(true);

        _logger.LogDebug("Waiting for images to be loaded");
        ct.ThrowIfCancellationRequested();
        await page.WaitForSelectorAsync("img");
        _logger.LogDebug("Images loaded");

        await page.WaitForNetworkIdleAsync();
    }

[kblok]

@skalahonza what happens when you print to PDF in chrome?

[skalahonza]

@kblok that works well

[mstijak]

This can happen if you're loading images over HTTPS while the page is served over HTTP.

[skalahonza]

As others suggested in other issues. I enabled ignoring of https errors for local development.

[skalahonza]

For those encountering similar issues, the problem was lazy loading. Images not initially visible on the page with lazy loading activated failed to render.

<img loading="lazy" src="data:image/png;base64,iVBORw0KGgoAA...">

Removing the lazy loading attribute from the image element resolved the issue, and PDF generation functioned properly once more.