Reverse (remove) smoothing filter

Question

I have a set of smooth black and white PNG images. I need to know how to programmatically return the smoothing effect and get sharp edges again.

I use GDI +, but I'm less interested in the code. I need an algorithm, perhaps a convolution filter, if such a matrix can be built.

Grayscale images (should) contain only 6 colors (or different shades of gray). This means that later I can recolor them using the Color-Lookup filter. However, when saving images, Photoshop automatically applied anti-aliasing, so the edges were blurred (because the bipolar interpolation mode was turned on). I need to return this effect.

Here is an example:

This is a screenshot from Photoshop.

- Sharpen, Photoshop. :

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EDIT:

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:

    private static void Resample(Bitmap bmp)
    {
        // First we look for the most prominent colors
        // i.e. They make up at least 1% of the image
        Hashtable stats = new Hashtable();

        for (int x = 0; x < bmp.Width; x++)
        {
            for (int y = 0; y < bmp.Height; y++)
            {
                Color px = bmp.GetPixel(x, y);
                if (px.A == 0)
                    continue;

                Color pxS = Color.FromArgb(255, px);
                if (stats.ContainsKey(pxS.ToArgb()))
                    stats[pxS.ToArgb()] = (int)stats[pxS.ToArgb()] + 1;
                else
                    stats.Add(pxS.ToArgb(), 1);
            }
        }

        float totalSize = bmp.Width*bmp.Height;
        float minAccepted = 0.01f;
        List<int> selectedColors = new List<int>();

        // Make up a list with the selected colors
        foreach (int key in stats.Keys)
        {
            int total = (int)stats[key];
            if (((float)total / totalSize) > minAccepted)
                selectedColors.Add(key);
        }

        // Keep growing the zones with the selected colors to cover the invalid colors created by the anti-aliasing
        while (GrowSelected(bmp, selectedColors));
    }

    private static bool GrowSelected(Bitmap bmp, List<int> selectedColors)
    {
        bool flag = false;

        for (int x = 0; x < bmp.Width; x++)
        {
            for (int y = 0; y < bmp.Height; y++)
            {
                Color px = bmp.GetPixel(x, y);
                if (px.A == 0)
                    continue;

                Color pxS = Color.FromArgb(255, px);

                if (selectedColors.Contains(pxS.ToArgb()))
                {
                    if (!isBackedByNeighbors(bmp, x, y))
                        continue;

                    List<Point> neighbors = GetNeighbors(bmp, x, y);
                    foreach(Point p in neighbors)
                    {
                        Color n = bmp.GetPixel(p.X, p.Y);
                        if (!isBackedByNeighbors(bmp, p.X, p.Y))
                            bmp.SetPixel(p.X, p.Y, Color.FromArgb(n.A, pxS));
                    }
                }
                else
                {
                    flag = true;
                }
            }
        }

        return flag;
    }

    private static List<Point> GetNeighbors(Bitmap bmp, int x, int y)
    {
        List<Point> neighbors = new List<Point>();

        for (int i = x - 1; i > 0 && i <= x + 1 && i < bmp.Width; i++)
            for (int j = y - 1; j > 0 && j <= y + 1 && j < bmp.Height; j++)
                neighbors.Add(new Point(i, j));
        return neighbors;
    }

    private static bool isBackedByNeighbors(Bitmap bmp, int x, int y)
    {
        List<Point> neighbors = GetNeighbors(bmp, x, y);
        Color px = bmp.GetPixel(x, y);
        int similar = 0;
        foreach (Point p in neighbors)
        {
            Color n = bmp.GetPixel(p.X, p.Y);
            if (Color.FromArgb(255, px).ToArgb() == Color.FromArgb(255, n).ToArgb())
                similar++;
        }

        return (similar > 2);
    }

: : http://i.imgur.com/8foQwFe.png

De-anti-aliased : http://i.imgur.com/w6gELWJ.png

Answer 1

DeconVolution ( ).
:

• Non Blind Deconvolution - (, ).
• Blind Deconvolution. , ( LPF - ..).

( ) , ( "-" ).

, - - LPF, (HPF). "Sharper Image" "Enhanced Edges". Unsharp Mask:

• LPF ( STD). lpfImage.
• : diffImage = originalImage - lpfImage.
• " " : usmImage = originalImage + (alpha * diffImage)
  alpha - "".

Enjoy...

Answer 2

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6 .

PNG PNG.

, GDI + PNG, SDK, .