Morphological Transformations

[thuongmhh]

It seems that Morphological Transformations are missing in the library. It would be great if you could implement them.
https://docs.opencv.org/4.x/d9/d61/tutorial_py_morphological_ops.html

[tocsoft]

@thuongmhh We full accept pull requests so if you would like to implement the feature we would be more than willing to review and merge the implementation into the codebase.

[thuongmhh]

@tocsoft I'm new to this library, I don't know how to implement the feature. However, I can share my code to perform image erosion and dilation. I hope it helps.

internal static class PostProcessor
{
    public static void ApplyOpening(Image<L8> target)
    {
        ApplyErosion3x3(target);
        ApplyDilation3x3(target);
    }

    public static void ApplyErosion3x3(Image<L8> target)
    {
        using var source = target.Clone();
        source.ProcessPixelRows(target, (sourceAccessor, targetAccessor) =>
        {
            for (int y = 0; y < sourceAccessor.Height; y++)
            {
                var rowSource = sourceAccessor.GetRowSpan(y);
                var lastRowSource = y > 0 ? sourceAccessor.GetRowSpan(y - 1) : null;
                var nextRowSource = y + 1 < sourceAccessor.Height ? sourceAccessor.GetRowSpan(y + 1) : null;

                var rowTarget = targetAccessor.GetRowSpan(y);
                for (var x = 0; x < sourceAccessor.Width; x++)
                {
                    var min = rowSource[x].PackedValue;

                    // Min value from last row
                    if (lastRowSource != null)
                    {
                        if (x > 0 && lastRowSource[x - 1].PackedValue < min) min = lastRowSource[x - 1].PackedValue;
                        if (lastRowSource[x].PackedValue < min) min = lastRowSource[x].PackedValue;
                        if (x + 1 < sourceAccessor.Width && lastRowSource[x + 1].PackedValue < min) min = lastRowSource[x + 1].PackedValue;
                    }

                    // Min value from current row
                    if (x > 0 && rowSource[x - 1].PackedValue < min) min = rowSource[x - 1].PackedValue;
                    if (x + 1 < sourceAccessor.Width && rowSource[x + 1].PackedValue < min) min = rowSource[x + 1].PackedValue;

                    // Min value from next row
                    if (nextRowSource != null)
                    {
                        if (x > 0 && nextRowSource[x - 1].PackedValue < min) min = nextRowSource[x - 1].PackedValue;
                        if (nextRowSource[x].PackedValue < min) min = nextRowSource[x].PackedValue;
                        if (x + 1 < sourceAccessor.Width && nextRowSource[x + 1].PackedValue < min) min = nextRowSource[x + 1].PackedValue;
                    }

                    rowTarget[x].PackedValue = min;
                }
            }
        });
    }

    public static void ApplyDilation3x3(Image<L8> target)
    {
        using var source = target.Clone();
        source.ProcessPixelRows(target, (sourceAccessor, targetAccessor) =>
        {
            for (int y = 0; y < sourceAccessor.Height; y++)
            {
                var rowSource = sourceAccessor.GetRowSpan(y);
                var lastRowSource = y > 0 ? sourceAccessor.GetRowSpan(y - 1) : null;
                var nextRowSource = y + 1 < sourceAccessor.Height ? sourceAccessor.GetRowSpan(y + 1) : null;

                var rowTarget = targetAccessor.GetRowSpan(y);
                for (var x = 0; x < sourceAccessor.Width; x++)
                {
                    var max = rowSource[x].PackedValue;

                    // Max value from last row
                    if (lastRowSource != null)
                    {
                        if (x > 0 && lastRowSource[x - 1].PackedValue > max) max = lastRowSource[x - 1].PackedValue;
                        if (lastRowSource[x].PackedValue > max) max = lastRowSource[x].PackedValue;
                        if (x + 1 < sourceAccessor.Width && lastRowSource[x + 1].PackedValue > max) max = lastRowSource[x + 1].PackedValue;
                    }

                    // Max value from current row
                    if (x > 0 && rowSource[x - 1].PackedValue > max) max = rowSource[x - 1].PackedValue;
                    if (x + 1 < sourceAccessor.Width && rowSource[x + 1].PackedValue > max) max = rowSource[x + 1].PackedValue;

                    // Max value from next row
                    if (nextRowSource != null)
                    {
                        if (x > 0 && nextRowSource[x - 1].PackedValue > max) max = nextRowSource[x - 1].PackedValue;
                        if (nextRowSource[x].PackedValue > max) max = nextRowSource[x].PackedValue;
                        if (x + 1 < sourceAccessor.Width && nextRowSource[x + 1].PackedValue > max) max = nextRowSource[x + 1].PackedValue;
                    }

                    rowTarget[x].PackedValue = max;
                }
            }
        });
    }
}