How to interpolatively resize down using bilinear sampling

[thegreatgramcracker]

Hello. I am trying to resize an image to 1/8 of it's resolution using bilinear resizing, but the code I expect to work doesn't seem to give the correct results.

MagickImage magickImage = new MagickImage(decompressedBytes);
magickImage.Settings.SetDefine(MagickFormat.Dds, "compression", "none");

magickImage.InterpolativeResize(magickImage.Width / 8, magickImage.Height / 8, PixelInterpolateMethod.Bilinear);

The result looks something like this (I upscaled to original size using nearest neighbor):

To me it doesn't appear to be resized using bilinear interpolation. Doing the same thing in Paint.NET looks like this:

I might be mistaken though because I'm not sure if there is more interpolation going on under the hood in Paint.NET, but if so then I am hoping to find out more how I can achieve a result similar to Paint.NET.

Any help or feedback would be greatly appreciated!

[dlemstra]

Can you share your input image? It looks like Paint.NET is just doing a normal resize?

[thegreatgramcracker]

I'm not able to attach a dds it seems but here is a png version of the original image. I actually managed to get a better result by just doing Resize() instead of InterpolativeResize(), and I added magickImage.Settings.SetDefine("filter", "sinc"); before I resized, which I'm not sure if I really set it right and if it made a difference. I'm fairly sure Paint.NET just did a normal bilinear interpolated resize, but my code in magick.NET didn't seem to use bilinear interpolation when I specified. Does InterpolativeResize() only work for upscaling?

[dlemstra]

You should use image.FilterType instead of that define. You can find more information about what InterpolativeResize does here: https://imagemagick.org/Usage/resize/#interpolative-resize.

[thegreatgramcracker]

Thank you, the link you provided gave me some helpful advice.