Question

I have a databound object within a WPF control that is ‘previewing’ a mutlipage tiff.

The object has a public PreviewImage, and CurrentPreviewPage.

It has a private PreviewPages which is a collection of MemoryStreams (each representing a page of the Tiff).

Upon the get of the PreviewImage (the first time) this code runs:

if (PreviewPages.Count == 0)
{
    Image myImg = System.Drawing.Image.FromFile(_LocalFile);

    for (int i = 0; i < (NumberOfPages); i++)
    {
        myImg.SelectActiveFrame(System.Drawing.Imaging.FrameDimension.Page, i);
        System.IO.MemoryStream ms = new System.IO.MemoryStream();
        myImg.Save(ms, System.Drawing.Imaging.ImageFormat.Tiff);
        PreviewPages.Add(ms);
    }
}

The previous code takes about 10 seconds to run for a 1100KB 17 page TIFF. There must be a better way of handling this.
Afterwards, this is called:

BitmapImage bi = new BitmapImage();
bi.BeginInit();
bi.DecodePixelWidth = 1000;
//bi.UriSource = new Uri(fiTemp.FullName);
bi.StreamSource = new System.IO.MemoryStream(PreviewPages[CurrentPreviewPage - 1].ToArray());
bi.EndInit();
_PreviewImage = bi;

Now, after the initialization this code works fantastically (it can change pages as fast as you can drag a bound slider). Any help would be much appreciated.

Answer 1

Load your first page on the primary thread and then additional pages in the background – see BackGroundWorker. Only primary thread can access the UI. On the BackGroundWorker you need to decide if you are going to get the pages 2-x one at a time or all at once. The user cannot get to page 2 until you bring page 2 to the UI thread. I would implement cancel. If the user gives up you don’t want to tie up CPU.