Exception Handling in PDF Rendering: Transitioning from PNG to JPEG

Aspose.PDF Product Family
1

Hi Team,

I am currently developing an application that renders a PDF to a display using JPEG format. However, we are encountering an exception when running the application.

Previously, the rendering function worked correctly when using a PNG device. To improve performance, we decided to switch to JPEG, but this change has resulted in the application failing.

Below, you will find the code snippet and a screenshot of the exception:
public void Aspose_RenderPagetoHDC(int pageID, IntPtr hdc, int width, int height)
{
Aspose.Pdf.Page page = pageDictionary[pageID].Item2;

Stream stream = pageDictionary[pageID].Item1;

Document pdfDocument = new Document(stream);
Aspose.Pdf.Page pdfPage;
try
{
    pdfPage = pdfDocument.Pages[1];

}
catch (Exception ex)
{
    return;
}

// Create a resolution object
Resolution resolution = new Resolution(72); // 300 DPI is a common resolution

// Create a MemoryStream to hold the rendered page
using (MemoryStream memStream = new MemoryStream())
{

    // Create a PngDevice with the specified width, height, and resolution
    //PngDevice pngDevice = new PngDevice(width, height, resolution);
    JpegDevice jpegDevice = new JpegDevice(resolution);
    try
    {
        // Render the page to the MemoryStream
        //Note: This pngDevice.Process api works only with System.Text.Encoding dll version 5.0.0.0 (depricated)and not latest version
        //pngDevice.Process(page, memStream);
        jpegDevice.Process(pdfPage, memStream);
    }
    catch (Exception ex)
    {
        // Log any exceptions
        return;
    }
    // Create a Bitmap from the MemoryStream
    using (Bitmap gdiBitmap = new Bitmap(memStream))
    {
        Graphics graphics;
        try
        {
            graphics = Graphics.FromHdc(hdc);
        }
        catch (Exception ex)
        {
            return;
        }
        // Create a Graphics object from the HDC handle
        using (graphics)
        {
            // Draw the bitmap onto the HDC
            graphics.DrawImage(gdiBitmap, 0, 0, width, height);
        }
    }
}

}

image.png (7.3 KB)

Any input would be a great help.

Regards,
Ramya.B

2

@Ramya_Bangalore

It seems that you are encountering an exception when trying to render a PDF document to JPEG format using Aspose.PDF, while the same functionality works correctly with PNG format. Here are a few suggestions to help you troubleshoot and resolve the issue:

  1. Check Exception Details: Make sure to log the exception details when the error occurs. This can provide insights into what might be going wrong. You can modify your catch block to log the exception message:

    catch (Exception ex)
{
    Console.WriteLine("Exception: " + ex.Message);
    return;
}

  2. Resolution and Quality Settings: Ensure that the resolution and quality settings for the JPEG device are appropriate. In your code, you are using a resolution of 72 DPI. You might want to try a higher resolution, such as 300 DPI, which is commonly used for better quality:

    Resolution resolution = new Resolution(300); // Set to 300 DPI
JpegDevice jpegDevice = new JpegDevice(resolution, 100); // 100 is maximum quality

  3. MemoryStream Usage: When using a MemoryStream, ensure that you reset the position of the stream before reading from it. After processing the page, you can reset the stream position like this:

    memStream.Position = 0; // Reset the position before creating Bitmap

  4. Example Code: Here is a simplified example of how to convert a PDF page to a JPEG image:

    using (MemoryStream memStream = new MemoryStream())
{
    // Create a JpegDevice with specified resolution and quality
    JpegDevice jpegDevice = new JpegDevice(resolution, 100);
    jpegDevice.Process(pdfPage, memStream);
    memStream.Position = 0; // Reset position

    using (Bitmap gdiBitmap = new Bitmap(memStream))
    {
        // Draw the bitmap onto the HDC
        using (Graphics graphics = Graphics.FromHdc(hdc))
        {
            graphics.DrawImage(gdiBitmap, 0, 0, width, height);
        }
    }
}

  5. Testing with Different PDFs: If possible, test your code with different PDF documents to see if the issue is specific to a particular file. Some PDFs may have content that is not handled well by the JPEG rendering process.

If you continue to face issues, please provide the specific exception message you are encountering, as it will help in diagnosing the problem further.

Feel free to reach out if you need more assistance!

Sources: