UndertaleModLib overlay hitboxes on sprites

SpriteOverlayer.cs

using System;
using System.Collections.Generic;
using System.Diagnostics;
using System.Drawing;
using System.Drawing.Drawing2D;
using System.Drawing.Imaging;
using System.IO;
using System.Linq;
using System.Runtime.InteropServices;
using System.Text;
using System.Threading.Tasks;
using UndertaleModLib;
using UndertaleModLib.Models;

namespace SpriteOverlayer
{
    class Program
    {
        static void Main(string[] args)
        {
            UndertaleData data = UndertaleIO.Read(new FileStream(@"C:\Users\krzys\Documents\Visual Studio 2017\Projects\UndertaleModTool\Test\bin\Debug\deltarune\triple.win", FileMode.Open));
            Dictionary<UndertaleEmbeddedTexture, Image> modifiedTextures = new Dictionary<UndertaleEmbeddedTexture, Image>();
            Dictionary<UndertaleEmbeddedTexture, Image> originalTextures = new Dictionary<UndertaleEmbeddedTexture, Image>();
            foreach (var sprite in data.Sprites)
            {
                if (sprite.BBoxMode != 2)
                    continue;

                Bitmap hitbox = new Bitmap((int)sprite.Width, (int)sprite.Height, PixelFormat.Format32bppArgb);
                for (int y = 0; y < sprite.Height; ++y)
                {
                    int row_start = (int)((sprite.Width + 7) / 8) * y;
                    for (int x = 0; x < sprite.Width; ++x)
                    {
                        int bytenum = row_start + x / 8;
                        int bitnum = x % 8;
                        hitbox.SetPixel(x, y, (sprite.CollisionMasks[0].Data[bytenum] & (1 << (7-bitnum))) != 0 ? Color.GreenYellow : Color.Transparent);
                    }
                }

                foreach(var frame in sprite.Textures)
                {
                    if (frame.Texture.SourceWidth != frame.Texture.TargetWidth || frame.Texture.TargetWidth != frame.Texture.BoundingWidth || frame.Texture.SourceWidth != frame.Texture.BoundingWidth ||
                        frame.Texture.SourceHeight != frame.Texture.TargetHeight || frame.Texture.TargetHeight != frame.Texture.BoundingHeight || frame.Texture.SourceHeight != frame.Texture.BoundingHeight)
                        continue;

                    Debug.WriteLine(sprite.Name.Content + " " + sprite.Textures.IndexOf(frame));

                    if (!modifiedTextures.ContainsKey(frame.Texture.TexturePage))
                    {
                        using (var stream = new MemoryStream(frame.Texture.TexturePage.TextureData.TextureBlob))
                        {
                            originalTextures.Add(frame.Texture.TexturePage, Image.FromStream(stream));
                            modifiedTextures.Add(frame.Texture.TexturePage, Image.FromStream(stream));
                        }
                    }

                    Graphics g = Graphics.FromImage(modifiedTextures[frame.Texture.TexturePage]);
                    g.CompositingMode = CompositingMode.SourceCopy;
                    ImageAttributes transparent = new ImageAttributes();
                    ColorMatrix mat = new ColorMatrix();
                    mat.Matrix33 = 0.25f;
                    transparent.SetColorMatrix(mat, ColorMatrixFlag.Default, ColorAdjustType.Bitmap);
                    g.DrawImage(originalTextures[frame.Texture.TexturePage], new Rectangle(frame.Texture.SourceX, frame.Texture.SourceY, frame.Texture.SourceWidth, frame.Texture.SourceHeight), frame.Texture.SourceX, frame.Texture.SourceY, frame.Texture.SourceWidth, frame.Texture.SourceHeight, GraphicsUnit.Pixel, transparent);
                    g.CompositingMode = CompositingMode.SourceOver;
                    g.DrawImage(hitbox, frame.Texture.SourceX, frame.Texture.SourceY);
                    g.Dispose();
                }

                hitbox.Dispose();
            }

            foreach(var tex in modifiedTextures)
            {
                //tex.Value.Save("R:\\" + data.EmbeddedTextures.IndexOf(tex.Key) + ".png");
                using (MemoryStream ms = new MemoryStream())
                {
                    tex.Value.Save(ms, ImageFormat.Png);
                    tex.Key.TextureData.TextureBlob = ms.ToArray();
                }
            }

            UndertaleIO.Write(new FileStream(@"C:\Users\krzys\Documents\Visual Studio 2017\Projects\UndertaleModTool\Test\bin\Debug\deltarune\triple_masked.win", FileMode.Create), data);
        }
    }
}