using System;
using System.Collections.Generic;
using System.Drawing;
using System.Drawing.Imaging;

public static class SplitSprites
{
    // Split a transparent PNG holding several objects side by side into one trimmed PNG per object
    // (columns separated by at least `gap` fully transparent columns), each scaled to fit maxH.
    public static void Run(string src, string dstPrefix, int gap, int maxH)
    {
        using (var b = new Bitmap(src))
        {
            int w = b.Width, h = b.Height;
            var col = new bool[w];
            var rect = new Rectangle(0, 0, w, h);
            var data = b.LockBits(rect, ImageLockMode.ReadOnly, PixelFormat.Format32bppArgb);
            var px = new byte[w * h * 4];
            System.Runtime.InteropServices.Marshal.Copy(data.Scan0, px, 0, px.Length);
            b.UnlockBits(data);
            for (int x = 0; x < w; x++) for (int y = 0; y < h; y++) if (px[(y * w + x) * 4 + 3] > 16) { col[x] = true; break; }
            var runs = new List<int[]>();
            int s = -1, lastOn = -1000;
            for (int x = 0; x < w; x++)
            {
                if (!col[x]) continue;
                if (s < 0) s = x;
                else if (x - lastOn > gap) { runs.Add(new[] { s, lastOn }); s = x; }
                lastOn = x;
            }
            if (s >= 0) runs.Add(new[] { s, lastOn });
            int n = 0;
            foreach (var r in runs)
            {
                int top = h, bot = 0;
                for (int x = r[0]; x <= r[1]; x++) for (int y = 0; y < h; y++) if (px[(y * w + x) * 4 + 3] > 16) { if (y < top) top = y; if (y > bot) bot = y; }
                int cw = r[1] - r[0] + 1, ch = bot - top + 1;
                double k = Math.Min(1.0, maxH / (double)ch);
                int ow = (int)Math.Round(cw * k), oh = (int)Math.Round(ch * k);
                n++;
                using (var o = new Bitmap(ow, oh, PixelFormat.Format32bppArgb))
                using (var g = Graphics.FromImage(o))
                {
                    g.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.HighQualityBicubic;
                    g.PixelOffsetMode = System.Drawing.Drawing2D.PixelOffsetMode.HighQuality;
                    g.Clear(Color.Transparent);
                    g.DrawImage(b, new Rectangle(0, 0, ow, oh), new Rectangle(r[0], top, cw, ch), GraphicsUnit.Pixel);
                    o.Save(dstPrefix + n + ".png", ImageFormat.Png);
                }
                Console.WriteLine(n + ": x " + r[0] + "-" + r[1] + " y " + top + "-" + bot + " -> " + ow + "x" + oh);
            }
        }
    }
}