feat : rework with the logic again, use skiasharp instead

Services/Utilities/CoordinateHelper.cs

@@ -0,0 +1,60 @@
+using System.Text.RegularExpressions;
+
+namespace StitcherApi.Services.Utilities;
+
+public static class CoordinateHelper
+{
+    private static readonly Regex CoordRegex = new(@"([A-Z]+)(\d+)", RegexOptions.Compiled);
+
+    public static (int startRow, int endRow, int startCol, int endCol) ParseCanvasRect(
+        string rectStr
+    )
+    {
+        var parts = rectStr.Split(':');
+        if (parts.Length != 2)
+        {
+            throw new ArgumentException("Invalid canvas_rect format. Expected format 'A1:H12'.");
+        }
+
+        var (r1, c1) = ParseSingleCoordinate(parts[0]);
+        var (r2, c2) = ParseSingleCoordinate(parts[1]);
+
+        return (Math.Min(r1, r2), Math.Max(r1, r2), Math.Min(c1, c2), Math.Max(c1, c2));
+    }
+
+    public static string IndexToRow(int index)
+    {
+        index++;
+        var result = "";
+        while (index > 0)
+        {
+            int remainder = (index - 1) % 26;
+            result = (char)('A' + remainder) + result;
+            index = (index - 1) / 26;
+        }
+        return result;
+    }
+
+    private static (int row, int col) ParseSingleCoordinate(string coord)
+    {
+        var match = CoordRegex.Match(coord);
+        if (!match.Success)
+        {
+            throw new ArgumentException($"Invalid coordinate format: '{coord}'.");
+        }
+
+        string rowStr = match.Groups[1].Value;
+        int col = int.Parse(match.Groups[2].Value) - 1;
+        return (RowToIndex(rowStr), col);
+    }
+
+    private static int RowToIndex(string rowStr)
+    {
+        int index = 0;
+        foreach (char c in rowStr)
+        {
+            index = index * 26 + (c - 'A' + 1);
+        }
+        return index - 1;
+    }
+}