Best options for image resizing

Question

Hi, I have resize images exceeding a max size. Methods I tried so far are not good enough :-(

1. System.Drawing.Image.GetThumbnailImage generates very poor quality images in general.
2. Playing with options like this one I can generate better images in quality but heavier than the original one.

Probably the second option (or something similar) is the best option and I would need to resize using the proper options.

Any advice?

EDIT
My option 2 was generating heavier images for some specific pictures. In general is working as expected so I'd say this is solved.

Answer 1

Create a new Bitmap object, then using the Graphics object, re-draw the old image into the new image's buffer at the increased/decreased size based on the resize engine you want.

// inImage is your original
Bitmap outImage = new Bitmap(newWid, newHei);

Graphics gfx = Graphics.FromImage(outImage);
gfx.InterpolationMode = InterpolationMode.HighQualityBicubic;

gfx.DrawImage(inImage,
   new Rectangle(0, 0, newWid, new Hei),
   new Rectangle(0, 0, inImage.Width, inImage.Height),
   GraphicsUnit.Pixel);

Answer 2

Try something like this:

public Bitmap Resize(Bitmap originalImage, int newWidth)
{
    int newHeight = (int)Math.Round(originalImage.Height * (decimal)newWidth / originalImage.Width, 0);
    var destination = new Bitmap(newWidth, newHeight);
    using (Graphics g = Graphics.FromImage(destination))
    {
        g.SmoothingMode = SmoothingMode.AntiAlias;
        g.InterpolationMode = InterpolationMode.HighQualityBicubic;
        g.PixelOffsetMode = PixelOffsetMode.HighQuality;
        g.DrawImage(originalImage, 0, 0, newWidth, newHeight);
    }
    return destination;
}

Answer 3

I would go with using the WPF libs instead of the GDI+ libs. The WPF libs perform faster and I think they yield better results compared to the GDI+ libs.

Check out these excellent posts from Bertrand Le Roy.

• Resizing images from the server using WPF/WIC instead of GDI+
• Server-side resizing with WPF: now with JPG
• The fastest way to resize images from ASP.NET. And it’s (more) supported-ish