How to deal with loss of image details after saving (.NET Bitmap)?

Question

.NET

I save images to disk, the same image can be of different resolutions.
In case of sufficient resolution, the image does not lose details:

At a lower resolution, details are lost after saving:

Are there any algorithms for saving in such a way that at least 1px wide lines remain?

Answer 1

Depends on what format you save the image in. If you need lossless, then I recommend using the PNG format.

Answer 2

Do you resize through System.Drawing.Graphics? Try playing with SmoothingMode, InterpolationMode, PixelOffsetMode:

var newBmp = new Bitmap(newWidth, newHeight);
using (Graphics g = Graphics.FromImage(newBmp)) {
    g.SmoothingMode = SmoothingMode.HighQuality;
    g.InterpolationMode = InterpolationMode.HighQualityBicubic; // или HighQualityBilinear
    g.PixelOffsetMode = PixelOffsetMode.HighQuality;
    g.DrawImage(oldBmp, new Rectangle(0, 0, newWidth, newHeight));
}