まえがき

【自分用】Microsoft Teamsのチャットログを無理やり保存する（自動スクロールしながら画面キャプチャするツールつくってみた） - Qiita
の補助用ツール
超てきとうコーディングなのであしからず。
スクリーンショット

Trim!ボタンでトリミング結果を保存します。
ソースコード

ImagesTrimmer.cs

using System;
using System.Collections;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Diagnostics;
using System.Drawing;
using System.Drawing.Drawing2D;
using System.Drawing.Imaging;
using System.IO;
using System.Reflection;
using System.Runtime.InteropServices;
using System.Text;
using System.Text.RegularExpressions;
using System.Threading;
using System.Threading.Tasks;
using System.Windows.Forms;

class MainForm : Form
{
    class NativeMethods
    {
        [DllImport("user32.dll")]
        [return: MarshalAs(UnmanagedType.Bool)]
        public static extern bool SetProcessDPIAware();
    }
    PictureBox pct;
    ListView lsvFiles;
    NumericUpDown nudScale;
    NumericUpDown nudBoundLeft;
    NumericUpDown nudBoundTop;
    NumericUpDown nudBoundRight;
    NumericUpDown nudBoundBottom;

    Image _imgPreviewCache;
    Rectangle _imgPreviewRect;
    bool _disableNudEvent;

    MainForm()
    {
        NativeMethods.SetProcessDPIAware();

        //Text = ;
        ClientSize = new Size(1100, 700);

        nudScale = new NumericUpDown(){
            Location = new Point(0, 0),
            Width = 100,
            Maximum = 100,
            Value = 50,
            Minimum = 10
        };
        nudScale.ValueChanged += (s,e)=>{ShowScaledPreviewImage();};
        Controls.Add(nudScale);


        Button btn = new Button(){
            Location = new Point(170, 0),
            Size = new Size(100, 30),
            Text = "Trim!",
        };
        btn.Click += (s,e)=>{TrimAndSaveImages();};
        Controls.Add(btn);


        Controls.Add(nudBoundLeft = new NumericUpDown(){
            Location = new Point(0, 25), Width = 60,
            Maximum = 50000,   Value = 0,   Minimum = 0
        });
        Controls.Add(nudBoundTop = new NumericUpDown(){
            Location = new Point(70, 25), Width = 60,
            Maximum = 50000,   Value = 0,   Minimum = 0
        });
        Controls.Add(nudBoundRight = new NumericUpDown(){
            Location = new Point(140, 25), Width = 60,
            Maximum = 50000,   Value = 1000,   Minimum = 0
        });
        Controls.Add(nudBoundBottom = new NumericUpDown(){
            Location = new Point(210, 25), Width = 60,
            Maximum = 50000,   Value = 700,   Minimum = 0
        });
        nudBoundLeft.ValueChanged   += (s,e)=>{if(!_disableNudEvent){RedrawBound();}};
        nudBoundTop.ValueChanged    += (s,e)=>{if(!_disableNudEvent){RedrawBound();}};
        nudBoundRight.ValueChanged  += (s,e)=>{if(!_disableNudEvent){RedrawBound();}};
        nudBoundBottom.ValueChanged += (s,e)=>{if(!_disableNudEvent){RedrawBound();}};


        lsvFiles = new ListView(){
            Location = new Point(0, 50),
            Size = new Size(300, 650),
            View = View.Details,
            FullRowSelect = true,
            GridLines = true,
            HideSelection = false,
        };
        lsvFiles.Columns.Add("Name", 250);
        //lsvFiles.Columns.Add("W x H", 100);
        lsvFiles.SelectedIndexChanged += (s,e)=>{LsvFiles_SelectedIndexChanged();};
        Controls.Add(lsvFiles);


        pct = new PictureBox(){
            Location = new Point(300, 0),
            Size = new Size(800, 700),
            Image = new Bitmap(800, 700),
        };
        pct.MouseDown += Pct_MouseDown;
        Controls.Add(pct);

        Load += (s,e)=>{LoadImageList();};
    }

    void LoadImageList()
    {
        lsvFiles.Items.Clear();

        string[] filenames = Directory.GetFiles(@"img/", "TeamsCapture*.png", SearchOption.TopDirectoryOnly);
        
        Array.Sort<string>(filenames, delegate(string a, string b)
        {
            return String.Compare(a, b, true); // ignore case
        });

        lsvFiles.BeginUpdate();
        try {
            foreach ( string filename in filenames ) {
                lsvFiles.Items.Add(new ListViewItem(new string[]{filename}));
            }
        }
        finally {
            lsvFiles.EndUpdate();
        }
    }
    
    void LsvFiles_SelectedIndexChanged()
    {
        var tmp = lsvFiles.SelectedIndices;
        if (tmp.Count != 1) {
            return;
        }
        
        if(_imgPreviewCache!=null){
            _imgPreviewCache.Dispose();
        }
        _imgPreviewCache = Image.FromFile(lsvFiles.Items[tmp[0]].Text);
        
        ShowScaledPreviewImage();
    }


    void ShowScaledPreviewImage()
    {
        float zoomRatio = ((float)nudScale.Value)/100;

        Graphics g = Graphics.FromImage(pct.Image);
        g.FillRectangle(Brushes.White,0,0,pct.Image.Width,pct.Image.Height);

        if ( _imgPreviewCache != null ) {
            
            _imgPreviewRect.Width  = (int)Math.Round(_imgPreviewCache.Width * zoomRatio);
            _imgPreviewRect.Height = (int)Math.Round(_imgPreviewCache.Height * zoomRatio);
            g.DrawImage(_imgPreviewCache, _imgPreviewRect);
        }
        int left   = (int)nudBoundLeft.Value;
        int top    = (int)nudBoundTop.Value;
        int right  = (int)nudBoundRight.Value;
        int bottom = (int)nudBoundBottom.Value;
        if(left>right){int tmp=left;left=right;right=tmp;}
        if(top>bottom){int tmp=top;top=bottom;bottom=tmp;}
        Pen pen = new Pen(Color.Blue, 3.0f);
        g.DrawRectangle(pen, left*zoomRatio, top*zoomRatio, (right-left)*zoomRatio, (bottom-top)*zoomRatio);
        g.Dispose();

        pct.Refresh();
    }

    void RedrawBound()
    {
        ShowScaledPreviewImage();
    }

    void Pct_MouseDown(object sender, MouseEventArgs e)
    {
        float zoomRatioInverse = 100/((float)nudScale.Value);

        if(e.Button == MouseButtons.Left) {
            _disableNudEvent = true;
            nudBoundLeft.Value = (int)(e.X*zoomRatioInverse);
            _disableNudEvent = false;
            nudBoundTop.Value  = (int)(e.Y*zoomRatioInverse);
        }
        else {
            _disableNudEvent = true;
            nudBoundRight.Value = (int)(e.X*zoomRatioInverse);
            _disableNudEvent = false;
            nudBoundBottom.Value  = (int)(e.Y*zoomRatioInverse);
        }
    }

    void TrimAndSaveImages()
    {
        Rectangle rect;
        {
            int left = (int)nudBoundLeft.Value;
            int top  = (int)nudBoundTop.Value;
            int right = (int)nudBoundRight.Value;
            int bottom = (int)nudBoundBottom.Value;
            if(left>right){int tmp=left;left=right;right=tmp;}
            if(top>bottom){int tmp=top;top=bottom;bottom=tmp;}
            rect = new Rectangle(left,top,right-left,bottom-top);
        }
        
        int cnt = 0;
        foreach(ListViewItem item in lsvFiles.Items) {
            string filename = item.Text;
            string destFileName = @"trimmed/"+cnt.ToString().PadLeft(6,'0')+".png";
            var img = Image.FromFile(filename);
            Bitmap bmp = new Bitmap(rect.Width, rect.Height);
            var g = Graphics.FromImage(bmp);
            //public void DrawImage (System.Drawing.Image image, int x, int y, System.Drawing.Rectangle srcRect, System.Drawing.GraphicsUnit srcUnit);
            g.DrawImage(img, 0, 0, rect, GraphicsUnit.Pixel);
            bmp.Save(destFileName, ImageFormat.Png);
            g.Dispose();
            img.Dispose();
            bmp.Dispose();
            cnt++;
        }
    }

    [STAThread]
    static void Main(string[] args)
    {
        Application.Run(new MainForm());
    }
}