将pdf页面转换为1000张以上的图像

Question

I could convert the pdf pages into images. if it is less than 50 pages its working fast... if any pdf large than 1000 pages... it acquires lot of time to complete. any one can review this code and make it work for large file size... i have used PdfLibNet dll(will not work in 4.0) in .NET3.5 here is my sample code:

public void ConverIMG(string filename)
    {          
        PDFWrapper wrapper = new PDFWrapper();
        wrapper.RenderDPI = Dpi;
        wrapper.LoadPDF(filename);
        int count = wrapper.PageCount;
        for (int i = 1; i <= wrapper.PageCount; i++)
        {
            string fileName = AppDomain.CurrentDomain.BaseDirectory + @"IMG\" + i.ToString() + ".png";
            wrapper.ExportJpg(fileName, i, i, (double)100, 100);
            while (wrapper.IsJpgBusy)
            {
                Thread.Sleep(50);
            }
        }
        wrapper.Dispose();            
    }

PS: we need to split pages and convert to images parallely and we need to get completed status.

Answer 1

If PDFWrapper performance degrades for documents bigger then 50 pages it suggests it is not very well written. To overcome this you could do conversion in 50 page batches and recreate PDFWrapper after each batch. There is an assumption that ExportJpg() gets slower with number of calls and its initial speed does not depend on the size of PDF.

This is only a workaround for apparent problems in PDFWrapper and a proper solution would be to use a fixed library. Also I would suggest Thread.Sleep(1) if you really need to wait with yielding.

public void ConverIMG(string filename)
{
    PDFWrapper wrapper = new PDFWrapper();
    wrapper.RenderDPI = Dpi;
    wrapper.LoadPDF(filename);
    int count = wrapper.PageCount;
    for (int i = 1; i <= count; i++)
    {
        string fileName = AppDomain.CurrentDomain.BaseDirectory + @"IMG\" + i.ToString() + ".png";
        wrapper.ExportJpg(fileName, i, i, (double) 100, 100);
        while (wrapper.IsJpgBusy)
        {
            Thread.Sleep(1);
        }

        if (i % 50 == 0)
        {
            wrapper.Dispose();
            wrapper = new PDFWrapper();
            wrapper.RenderDPI = Dpi;
            wrapper.LoadPDF(filename);
        }
    }
    wrapper.Dispose();
}