High quality image resize (C#)

You can use this class to resize images proportionally (maintaining aspect ratio), or to resize an image to an exact size and crop off excess (useful for making nice thumbnails):

public static class ImageExt {

  public static Image Resize(this Image img, int srcX, int srcY, int srcWidth, int srcHeight, int dstWidth, int dstHeight) {

    var bmp = new Bitmap(dstWidth, dstHeight);

    using(var graphics = Graphics.FromImage(bmp)) {

      graphics.InterpolationMode = InterpolationMode.HighQualityBicubic;

      graphics.CompositingMode = CompositingMode.SourceCopy;

      graphics.PixelOffsetMode = PixelOffsetMode.HighQuality;

      using(var wrapMode = new ImageAttributes()) {

        wrapMode.SetWrapMode(WrapMode.TileFlipXY);

        var destRect = new Rectangle(0, 0, dstWidth, dstHeight);

        graphics.DrawImage(img, destRect, srcX, srcY, srcWidth, srcHeight, GraphicsUnit.Pixel, wrapMode);

      }

    }

    return bmp;

  }



  public static Image ResizeProportional(this Image img, int width, int height, bool enlarge = false) {

    double ratio = Math.Max(img.Width / (double) width, img.Height / (double) height);

    if (ratio < 1 && !enlarge) return img;

    return img.Resize(0, 0, img.Width, img.Height, M2.Round(img.Width / ratio), M2.Round(img.Height / ratio));

  }

  public static Image ResizeCropExcess(this Image img, int dstWidth, int dstHeight) {

    double srcRatio = img.Width / (double) img.Height;

    double dstRatio = dstWidth / (double) dstHeight;

    int srcX,

    srcY,

    cropWidth,

    cropHeight;

    if (srcRatio < dstRatio) // trim top and bottom 

    {

      cropHeight = dstHeight * img.Width / dstWidth;

      srcY = (img.Height - cropHeight) / 2;

      cropWidth = img.Width;

      srcX = 0;

    } else // trim left and right 

    {

      cropWidth = dstWidth * img.Height / dstHeight;

      srcX = (img.Width - cropWidth) / 2;

      cropHeight = img.Height;

      srcY = 0;

    }

    return Resize(img, srcX, srcY, cropWidth, cropHeight, dstWidth, dstHeight);

  }

}