如何调整图像大小而不会降低质量

Question

I have a big image in good quality (for my needs), i need resize to small size (30 x 30px), I resize it with graphic.DrawImage. But when i resize it become blurred and little lighter. also I have try CompositingQuality and InterpolationMode, but it all was bad.

Example, that quality i'm trying get.

My result

Edited Image of icon i draw myself, maybe it will be better draw it small without resizing?

Edit2

Resizeing code:

                Bitmap tbmp;
                //drawing all my features in tbmp with graphics
                bmp = new Bitmap(width + 5, height + 5);
                bmp.MakeTransparent(Color.Black);
                using (var gg = Graphics.FromImage(bmp))
                {
                    gg.CompositingQuality = CompositingQuality.HighQuality;
                  //  gg.SmoothingMode = SmoothingMode.HighQuality;
                    gg.InterpolationMode = InterpolationMode.HighQualityBicubic;

                    gg.DrawImage(tbmp, new Rectangle(0, 0, width, height), new Rectangle(GXMin, GYMin, GXMax + 20, GYMax + 20), GraphicsUnit.Pixel);
                    gg.Dispose();
                }

Answer 1

I use this method as a way to get a thumbnail image (of any size) from an original (of any size). Note that there are inherent issues when you ask for a size ratio that varies greatly from that of the original. Best to ask for sizes that are in scale to one another:

public static Image GetThumbnailImage(Image OriginalImage, Size ThumbSize)
{
    Int32 thWidth = ThumbSize.Width;
    Int32 thHeight = ThumbSize.Height;
    Image i = OriginalImage;
    Int32 w = i.Width;
    Int32 h = i.Height;
    Int32 th = thWidth;
    Int32 tw = thWidth;
    if (h > w)
    {
        Double ratio = (Double)w / (Double)h;
        th = thHeight < h ? thHeight : h;
        tw = thWidth < w ? (Int32)(ratio * thWidth) : w;
    }
    else
    {
        Double ratio = (Double)h / (Double)w;
        th = thHeight < h ? (Int32)(ratio * thHeight) : h;
        tw = thWidth < w ? thWidth : w;
    }
    Bitmap target = new Bitmap(tw, th);
    Graphics g = Graphics.FromImage(target);
    g.SmoothingMode = SmoothingMode.HighQuality;
    g.CompositingQuality = CompositingQuality.HighQuality;
    g.InterpolationMode = InterpolationMode.High;
    Rectangle rect = new Rectangle(0, 0, tw, th);
    g.DrawImage(i, rect, 0, 0, w, h, GraphicsUnit.Pixel);
    return (Image)target;
}