image getting blurred when enlarging picture box

Question

I am developing an application for image processing. To zoom the image, I enlarge PictureBox. But after enlarging I get below image as result.

But I want result like below image

Here is my Code :

      picturebox1.Size = new Size((int)(height * zoomfactor), (int) 
      (width* zoomfactor));
      this.picturebox1.Refresh();

PictureBox uses InterpolationMode.Bilinear, you want NearestNeighbor. So you'll have to do this yourself. Google "c# resize bitmap" for basic hits. — Hans Passant, Mar 29 '18 at 12:14
It could be the image type that is the issue. If you expand the image then you are reducing the compression quality. Maybe this link might help https://stackoverflow.com/questions/12646287/image-scaling-of-picture-box — Jack Henry, Mar 29 '18 at 11:34

score 11 · Accepted Answer · edited Mar 29 '21 at 00:11

11

The PictureBox by itself will always create a nice and smooth version.

To create the effect you want you need to draw zoomed versions yourself. In doing this you need to set the

 Graphics.InterpolationMode = InterpolationMode.NearestNeighbor;

Then no blurring will happen..

Example:

private void trackBar1_Scroll(object sender, EventArgs e)
{
    Bitmap bmp = (Bitmap)pictureBox1.Image;
    Size sz = bmp.Size;
    Bitmap zoomed = (Bitmap)pictureBox2.Image;
    if (zoomed != null) zoomed.Dispose();

    float zoom = (float)(trackBar1.Value / 4f + 1);
    zoomed = new Bitmap((int)(sz.Width * zoom), (int)(sz.Height * zoom));

    using (Graphics g = Graphics.FromImage(zoomed))
    {
      if (cbx_interpol.Checked) g.InterpolationMode = InterpolationMode.NearestNeighbor;
      g.PixelOffsetMode = PixelOffsetMode.Half;

      g.DrawImage(bmp, new Rectangle( Point.Empty, zoomed.Size) );
    }
    pictureBox2.Image = zoomed;
}

Of course you need to avoid setting the PBox to Sizemode Zoom or Stretch!

edited Mar 29 '21 at 00:11

Danvil

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answered Mar 29 '18 at 12:33

TaW

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Thank alot for your answer. But it throws exception "parameter is not valid" on graphics.DrawImage(). – Siddhi Dave Mar 29 '18 at 12:50
Hm, strange. Is there a valid image in the 1st pixturebox? I.e. is `bmp` a valid image? – TaW Mar 29 '18 at 12:54
Yes bmp is valid image. – Siddhi Dave Mar 29 '18 at 12:57
Sorry its throw exception due to my code not from above mention code.Thanks for your help. It save lot of time. – Siddhi Dave Mar 29 '18 at 12:59
1

Ok sure. But my issue is resolved and i get my output. – Siddhi Dave Mar 29 '18 at 13:27
1

This has got to be one of the best SO answers out there! Example code and demo animation of it in action. Superb! – sonyisda1 Feb 14 '19 at 16:14
3

Note that for NearestNeighbor you need to set PixelOffsetMode to Half, otherwise the top and left edge eat half a pixel of your image. This is actually visible on the blue border above. – Nyerguds Jul 26 '19 at 07:32
@Nyerguds Modified the code to set PixelOffsetMode correctly. – Danvil Mar 29 '21 at 00:12

image getting blurred when enlarging picture box

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