How do I make a PictureBox use Nearest Neighbor resampling?

Question

I am using StretchImage because the box is resizable with splitters. It looks like the default is some kind of smooth bilinear filtering, causing my image to be blurry and h

Answer 1

When resizing an image in .net, the System.Drawing.Drawing2D.InterpolationMode offers the following resize methods:

• Bicubic
• Bilinear
• High
• HighQualityBicubic
• HighQualityBilinear
• Low
• NearestNeighbor
• Default

Answer 2

I did a MSDN search and turns out there's an article on this, which is not very detailed but outlines that you should use the paint event.

http://msdn.microsoft.com/en-us/library/k0fsyd4e.aspx

I edited a commonly available image zooming example to use this feature, see below

Edited from: http://www.dotnetcurry.com/ShowArticle.aspx?ID=196&AspxAutoDetectCookieSupport=1

Hope this helps

    private void Form1_Load(object sender, EventArgs e)
    {
        // set image location
        imgOriginal = new Bitmap(Image.FromFile(@"C:\images\TestImage.bmp"));
        picBox.Image = imgOriginal;

        // set Picture Box Attributes
        picBox.SizeMode = PictureBoxSizeMode.StretchImage;

        // set Slider Attributes
        zoomSlider.Minimum = 1;
        zoomSlider.Maximum = 5;
        zoomSlider.SmallChange = 1;
        zoomSlider.LargeChange = 1;
        zoomSlider.UseWaitCursor = false;

        SetPictureBoxSize();

        // reduce flickering
        this.DoubleBuffered = true;
    }

    // picturebox size changed triggers paint event
    private void SetPictureBoxSize()
    {
        Size s = new Size(Convert.ToInt32(imgOriginal.Width * zoomSlider.Value), Convert.ToInt32(imgOriginal.Height * zoomSlider.Value));
        picBox.Size = s;
    }


    // looks for user trackbar changes
    private void trackBar1_Scroll(object sender, EventArgs e)
    {
        if (zoomSlider.Value > 0)
        {
            SetPictureBoxSize();
        }
    }

    // redraws image using nearest neighbour resampling
    private void picBox_Paint_1(object sender, PaintEventArgs e)
    {
        e.Graphics.InterpolationMode = InterpolationMode.NearestNeighbor;
        e.Graphics.DrawImage(
           imgOriginal,
            new Rectangle(0, 0, picBox.Width, picBox.Height),
            // destination rectangle 
            0,
            0,           // upper-left corner of source rectangle
            imgOriginal.Width,       // width of source rectangle
            imgOriginal.Height,      // height of source rectangle
            GraphicsUnit.Pixel);
    }

Answer 3

I suspect you're going to have to do the resizing manually thru the Image class and DrawImage function and respond to the resize events on the PictureBox.

Answer 4

I needed this functionality also. I made a class that inherits PictureBox, overrides OnPaint and adds a property to allow the interpolation mode to be set:

using System.Drawing.Drawing2D;
using System.Windows.Forms;

/// <summary>
/// Inherits from PictureBox; adds Interpolation Mode Setting
/// </summary>
public class PictureBoxWithInterpolationMode : PictureBox
{
    public InterpolationMode InterpolationMode { get; set; }

    protected override void OnPaint(PaintEventArgs paintEventArgs)
    {
        paintEventArgs.Graphics.InterpolationMode = InterpolationMode;
        base.OnPaint(paintEventArgs);
    }
}