CODEWITHSUNDEEP
c#winformsbitmapbackgroundworkerpicturebox
dll
dll

Reputation: 161

How load image with backgroundworker and display to picturebox?

I have to display images in a picturebox. The images are high resolution scans of archives. Because of this high resolution my panning en zoom features are very slow. To solve this problem I reduced the bitmap width and length while maintaining the images readable. In my code in drawOriginalImage(); the variable "quality" is thus the factor which I reduce the size of the bitmap. This is how I did it:

private void drawOriginalImage(int quality) {
    try {
        int x = originalImage.Width / quality, 
            y = originalImage.Height / quality;
        pictureBox.Image = (Image)new Bitmap(originalImage, x, y);
        pictureBox.SizeMode = PictureBoxSizeMode.Zoom;
    }
    catch (Exception ex) {
        throw ex;
    }
}

But this solution brings another problem. This step can be very long:

pictureBox.Image = (Image)new Bitmap(originalImage, x, y);

Because of this slowness, I wanted to process this step with the Backgroundworker feature. Now my code looks like this:

private void drawOriginalImage(int quality) {
    Cursor = Cursors.AppStarting;
    backgroundWorker.RunWorkerAsync(new Point(
        originalImage.Width / quality,
        originalImage.Height / quality
    ));
}
private void backgroundWorker_DoWork(object sender, DoWorkEventArgs e) {
    Point p = (Point)e.Argument;
    e.Result = new Bitmap(originalImage, p.X, p.Y);
}
private void backgroundWorker_RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e) {
    if (e.Error != null) {
        MessageBox.Show("Image too big.\nOriginal error:\n" + e.Error);
    }
    else {
        pictureBox.Image = (Image)e.Result;
        pictureBox.SizeMode = PictureBoxSizeMode.Zoom;
        Cursor = Cursors.Default;
    }
}

But it doesn't work. I see the cursor changing from "Cursors.AppStarting" to "Cursors.Default" and thus the task is probably completed. But there is no image in my picturebox? How can that be? What am I doing wrong?

When I debug it, the program never goes in "backgroundWorker_RunWorkerCompleted". How can it be?

Upvotes: 0

Views: 1492

Answers (1)

dll
dll

Reputation: 161

I have found it. I had hook up all my events correctly by adding this:

backgroundWorker.DoWork += new DoWorkEventHandler(backgroundWorker_DoWork);
backgroundWorker.RunWorkerCompleted += new RunWorkerCompletedEventHandler(backgroundWorker_RunWorkerCompleted);

Upvotes: 1

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