Speed Up Application when Moving to the Next Page

Question

I’m using WinForms. In my Form I have a picture-box that displays image documents. These image documents have many pages. I have an open, next, and previous button on my form. The next button goes forward one page, and the previous button goes back one page in the document that’s opened in the picture-box. I also have labels on my form to indicate how much pages there are, and what page the user is currently viewing.

The problem with my code is when i open large image files into my picture-box, for example documents that has 1200 pages, and click next. The page loads up slow. I want to improve the performance of the code.

How can i make viewing the image documents faster or my code better?

I provided a tif document to test on: http://www.filedropper.com/sampletifdocument5pages

    private int int_Current_Page = 0;

    private void btnNextImage_Click_1(object sender, EventArgs e)
    {
        Image image2;
        try
        {
            if (int_Current_Page == Convert.ToInt32(lblNumPages.Text)) // if you have reached the last page it ends here
                                                                  // the "-1" should be there for normalizing the number of pages
            { int_Current_Page = Convert.ToInt32(lblNumPages.Text); }
            else
            {                   
                int_Current_Page++; //page increment

                using (FileStream stream = new FileStream(@"C:\my_Image_document", FileMode.Open, FileAccess.Read))
                {
                    image2 = Image.FromStream(stream);
                    Refresh_Image();
                } 
            }
        }
        catch(Exception ex)
        {
            MessageBox.Show(ex.Message);
        }
    }

    private void btnPrevImage_Click_1(object sender, EventArgs e)
    {
        if (int_Current_Page == 0) // it stops here if you reached the bottom, the first page of the tiff
        { int_Current_Page = 0; }
        else
        {
            int_Current_Page--; // if its not the first page, then go to the previous page
            Refresh_Image(); // refresh the image on the selected page
        }
    }

    private void openButton_Click_1(object sender, EventArgs e)
    {
        Refresh_Image(); //Opens the large image document
    }

    private void Refresh_Image()
    {
        Image myImg; // setting the selected tiff
        Image myBmp; // a new occurance of Image for viewing

        using (FileStream stream = new FileStream(@"C:\my_Image_document", FileMode.Open, FileAccess.Read))
        {
            myImg = Image.FromStream(stream);

            int intPages = myImg.GetFrameCount(System.Drawing.Imaging.FrameDimension.Page); // getting the number of pages of this tiff
            intPages--; // the first page is 0 so we must correct the number of pages to -1
            lblNumPages.Text = Convert.ToString(intPages); // showing the number of pages
            lblCurrPage.Text = Convert.ToString(int_Current_Page); // showing the number of page on which we're on

            myImg.SelectActiveFrame(System.Drawing.Imaging.FrameDimension.Page, int_Current_Page); // going to the selected page

            myBmp = new Bitmap(myImg, pictureBox1.Width, pictureBox1.Height);

            pictureBox1.Image = myBmp; // showing the page in the pictureBox1  
        }
    }

Answer 1

This is probably slowing down in one of two places, either loading the enormous file (hopefully) or Selecting the active frame. If it's the first issue, it's probably easy to fix just by lazy-loading the image one time:

private int int_Current_Page = 0;

private void btnNextImage_Click_1(object sender, EventArgs e)
{
    Image image2;
    try
    {
        if (int_Current_Page == Convert.ToInt32(lblNumPages.Text)) // if you have reached the last page it ends here
                                                              // the "-1" should be there for normalizing the number of pages
        { int_Current_Page = Convert.ToInt32(lblNumPages.Text); }
        else
        {                   
            int_Current_Page++; //page increment
            Refresh_Image();
        }
    }
    catch(Exception ex)
    {
        MessageBox.Show(ex.Message);
    }
}

private void btnPrevImage_Click_1(object sender, EventArgs e)
{
    if (int_Current_Page == 0) // it stops here if you reached the bottom, the first page of the tiff
    { int_Current_Page = 0; }
    else
    {
        int_Current_Page--; // if its not the first page, then go to the previous page
        Refresh_Image(); // refresh the image on the selected page
    }
}

private void openButton_Click_1(object sender, EventArgs e)
{
    Refresh_Image(); //Opens the large image document
}
FileStream _stream; 
Image _myImg; // setting the selected tiff
private void Refresh_Image()
{
    // Image myImg; // setting the selected tiff - Now a member variable
    Image myBmp; // a new occurance of Image for viewing

    if (_myImg == null)
    {
        _stream = new FileStream(@"C:\my_Image_document", FileMode.Open, FileAccess.Read)
        _myImg = Image.FromStream(_Stream);
    }
    int intPages = _myImg.GetFrameCount(System.Drawing.Imaging.FrameDimension.Page); // getting the number of pages of this tiff
    intPages--; // the first page is 0 so we must correct the number of pages to -1
    lblNumPages.Text = Convert.ToString(intPages); // showing the number of pages
    lblCurrPage.Text = Convert.ToString(int_Current_Page); // showing the number of page on which we're on

    _myImg.SelectActiveFrame(System.Drawing.Imaging.FrameDimension.Page, int_Current_Page); // going to the selected page

    myBmp = new Bitmap(_myImg, pictureBox1.Width, pictureBox1.Height);

    pictureBox1.Image = myBmp; // showing the page in the pictureBox1  
}

protected override void Dispose(bool disposing)
{
    if (_stream != null) _stream.Dispose();
    base.Dispose(disposing);
}