Question

I’m writing a control to show images.
My problem comes out using Image class on multipage TIFFs.
I use this (I post only relevant code) at the beginning:

Image img;
int pages;
img = Bitmap.FromFile(filename);
pages = img.GetFrameCount(FrameDimension.Page);

then, when the user wants to show a different page:

public override Image GetPage(int page)
{
    if (page < 1 || page > pages) return null;
    try
    {
        #if !TEST
            img.SelectActiveFrame(FrameDimension.Page, page - 1);
            return new Bitmap(img);
        #else
            MemoryStream ms = new MemoryStream();
            img.SelectActiveFrame(FrameDimension.Page, page - 1);
            img.Save(ms, ImageFormat.Jpeg);
            Image ret = Image.FromStream(ms);
            ms.Flush();
            ms.Dispose();
            return ret;
        #endif
    }
    catch (Exception ex)
    {
        "Tiff GetPage error: {0}".ToDebug(ex.Message);
        return null;
    }
}

Using img.SelectActiveFrame(FrameDimension.Page, page - 1); (in both versions) about 7MB are allocated in memory and those are never freed (even exiting the method)!!!
If I goes to next page 7MB are allocated and not freed everytime, while going back (on an already visited pages) previously allocated memory is used.
To give you an example: think Task Manager reports my app is using x MB; going one page forward memory increases to x + y (after SelectActiveFrame()) + z (Image ret = ...). Well, I should have x + z (y part should be zero or GC collected exiting the method), but obviously that’s not what happens, even calling GC.Collect manually.
Going back to a previously visited page, memory increases effectively only with z, as expected.
I find it terrible (think about a file with 80 pages…), but how can I force img object to free allocated memory? Am I doing something wrong?
I’ve already thought closing and reopening img, but speed is not good.
Thanks to everybody

Answer 1

If I’m not mistaken you’re not destroying the used controls at every possible point.
I think you might need to test this – but make sure that you’re disposing all the used controls.

ie. ImageControlUsed.Dispose();