c# 制作正方形圖檔

using System;
using System.Collections.Generic;
using System.Drawing;
using System.Drawing.Drawing2D;
using System.Drawing.Imaging;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace treads
{
    /// <summary>
    /// 制作小正方形
    /// </summary>
    class Class3
    {
        private string srcFileName = @"x";//擷取圖檔的路徑
        private string srcFileName1 = @"x";//要保持圖檔的新路徑

      

        /// <summary>
        /// 儲存圖檔
        /// </summary>
        /// <param name="image">Image 對象</param>
        /// <param name="savePath">儲存路徑</param>
        /// <param name="ici">指定格式的編解碼參數</param>
        private static void SaveImage(Image image, string savePath, ImageCodecInfo ici)
        {
            //設定 原圖檔 對象的 EncoderParameters 對象
            EncoderParameters parameters = new EncoderParameters(1);
            parameters.Param[0] = new EncoderParameter(System.Drawing.Imaging.Encoder.Quality, ((long)100));
            image.Save(savePath, ici, parameters);
            parameters.Dispose();
        }

        /// <summary>
        /// 擷取圖像編碼解碼器的所有相關資訊
        /// </summary>
        /// <param name="mimeType">包含編碼解碼器的多用途網際郵件擴充協定 (MIME) 類型的字元串</param>
        /// <returns>傳回圖像編碼解碼器的所有相關資訊</returns>
        private static ImageCodecInfo GetCodecInfo(string mimeType)
        {
            ImageCodecInfo[] CodecInfo = ImageCodecInfo.GetImageEncoders();
            foreach (ImageCodecInfo ici in CodecInfo)
            {
                if (ici.MimeType == mimeType)
                    return ici;
            }
            return null;
        }

        /// <summary>
        /// 計算新尺寸
        /// </summary>
        /// <param name="width">原始寬度</param>
        /// <param name="height">原始高度</param>
        /// <param name="maxWidth">最大新寬度</param>
        /// <param name="maxHeight">最大新高度</param>
        /// <returns></returns>
        private static Size ResizeImage(int width, int height, int maxWidth, int maxHeight)
        {
            //此次修改過=================
            if (maxWidth <= 0)
                maxWidth = width;
            if (maxHeight <= 0)
                maxHeight = height;
            //以上修改過=================
            decimal MAX_WIDTH = (decimal)maxWidth;
            decimal MAX_HEIGHT = (decimal)maxHeight;
            decimal ASPECT_RATIO = MAX_WIDTH / MAX_HEIGHT;

            int newWidth, newHeight;
            decimal originalWidth = (decimal)width;
            decimal originalHeight = (decimal)height;

            if (originalWidth > MAX_WIDTH || originalHeight > MAX_HEIGHT)
            {
                decimal factor;
                // determine the largest factor 
                if (originalWidth / originalHeight > ASPECT_RATIO)
                {
                    factor = originalWidth / MAX_WIDTH;
                    newWidth = Convert.ToInt32(originalWidth / factor);
                    newHeight = Convert.ToInt32(originalHeight / factor);
                }
                else
                {
                    factor = originalHeight / MAX_HEIGHT;
                    newWidth = Convert.ToInt32(originalWidth / factor);
                    newHeight = Convert.ToInt32(originalHeight / factor);
                }
            }
            else
            {
                newWidth = width;
                newHeight = height;
            }
            return new Size(newWidth, newHeight);
        }

        /// <summary>
        /// 得到圖檔格式
        /// </summary>
        /// <param name="name">檔案名稱</param>
        /// <returns></returns>
        public static ImageFormat GetFormat(string name)
        {
            string ext = name.Substring(name.LastIndexOf(".") + 1);
            switch (ext.ToLower())
            {
                case "jpg":
                case "jpeg":
                    return ImageFormat.Jpeg;
                case "bmp":
                    return ImageFormat.Bmp;
                case "png":
                    return ImageFormat.Png;
                case "gif":
                    return ImageFormat.Gif;
                default:
                    return ImageFormat.Jpeg;
            }
        }
     

        /// <summary>
        /// 制作小正方形
        /// </summary>
        /// <param name="image">圖檔對象</param>
        /// <param name="newFileName">新位址</param>
        /// <param name="newSize">長度或寬度</param>
        public static void MakeSquareImage(Image image, string newFileName, int newSize)
        {
            int i = 0;
            int width = image.Width;
            int height = image.Height;
            if (width > height)
                i = height;
            else
                i = width;

            Bitmap b = new Bitmap(newSize, newSize);

            try
            {
                Graphics g = Graphics.FromImage(b);
                //設定高品質插值法
                g.InterpolationMode = InterpolationMode.HighQualityBicubic;
                //設定高品質,低速度呈現平滑程度
                g.SmoothingMode = SmoothingMode.AntiAlias;
                g.PixelOffsetMode = PixelOffsetMode.HighQuality;
                //清除整個繪圖面并以透明背景色填充
                g.Clear(Color.Transparent);
                if (width < height)
                    g.DrawImage(image, new Rectangle(0, 0, newSize, newSize), new Rectangle(0, (height - width) / 2, width, width), GraphicsUnit.Pixel);
                else
                    g.DrawImage(image, new Rectangle(0, 0, newSize, newSize), new Rectangle((width - height) / 2, 0, height, height), GraphicsUnit.Pixel);

                SaveImage(b, newFileName, GetCodecInfo("image/" + GetFormat(newFileName).ToString().ToLower()));
            }
            finally
            {
                image.Dispose();
                b.Dispose();
            }
        }

        /// <summary>
        /// 制作小正方形
        /// </summary>
        /// <param name="fileName">圖檔檔案名</param>
        /// <param name="newFileName">新位址</param>
        /// <param name="newSize">長度或寬度</param>
        public static void MakeSquareImage(string fileName,string newFileName, int newSize)
        {
            MakeSquareImage(Image.FromFile(fileName), newFileName, newSize);
        }
    }
}      

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