C#学习笔记之以指定的大小缩放图片

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using System;using System.Collections.Generic;using System.Linq;using System.Text;using System.Drawing;using System.Drawing.Drawing2D;namespace QingdaoZenius{    class ScalPhoto    {        /// <summary>         /// 按照指定大小缩放图片，但是为了保证图片宽高比自动截取         /// </summary>         /// <param name="srcPath">原图片路径</param>         /// <param name="destWidth">目标图片宽</param>         /// <param name="destHeight">目标图片高</param>         /// <returns></returns>         public static Bitmap SizeImageWithOldPercent(string srcPath, int destWidth, int destHeight)        {            Image srcImage = Image.FromFile(srcPath);            try            {                // 要截取图片的宽度（原始宽度）                 int srcWidth = srcImage.Width;                // 要截取图片的高度（原始高度）                 int srcHeight = srcImage.Height;                // 截取开始横坐标                int newX = 0;                // 截取开始纵坐标                 int newY = 0;                // 截取比例                 double whPercent = ((double)destWidth / (double)destHeight) * ((double)srcImage.Height / (double)srcImage.Width);                if (whPercent > 1)                {                    // 当前图片宽度对于要截取比例过大时                     srcWidth = int.Parse(Math.Round(srcImage.Width / whPercent).ToString());                }                else if (whPercent < 1)                {                    // 当前图片高度对于要截取比例过大时                     srcHeight = int.Parse(Math.Round(srcImage.Height * whPercent).ToString());                }                if (srcWidth != srcImage.Width)                {                    // 宽度有变化时，调整开始截取的横坐标                     newX = Math.Abs(int.Parse(Math.Round(((double)srcImage.Width - srcWidth) / 2).ToString()));                }                else if (srcHeight == srcImage.Height)                {                    // 高度有变化时，调整开始截取的纵坐标                     newY = Math.Abs(int.Parse(Math.Round(((double)srcImage.Height - (double)srcHeight) / 2).ToString()));                }                // 将原始图片画到目标画布上，返回目标图片                Bitmap cutedImage = CutImage(srcImage, newX, newY, srcWidth, srcHeight);                // 在创建一个新的画布                Bitmap bmp = new Bitmap(destWidth, destHeight);                Graphics g = Graphics.FromImage(bmp);                // 插值算法的质量                 g.InterpolationMode = InterpolationMode.Default;                g.DrawImage(cutedImage, new Rectangle(0, 0, destWidth, destHeight), new Rectangle(0, 0, cutedImage.Width, cutedImage.Height), GraphicsUnit.Pixel);                g.Dispose();                return bmp;            }            catch (Exception)            {                return null;            }        }        /// <summary>         /// 剪裁 -- 用GDI+         /// </summary>         /// <param name="image">原始图片</param>         /// <param name="StartX">开始坐标X</param>         /// <param name="StartY">开始坐标Y</param>         /// <param name="destWidth">目标图片宽度</param>         /// <param name="destHeight">目标图片高度高度</param>         /// <returns>剪裁后的Bitmap</returns>         private static Bitmap CutImage(Image image, int StartX, int StartY, int destWidth, int destHeight)        {            int srcWidth = image.Width;            int srcHeight = image.Height;            if (StartX >= srcWidth || StartY >= srcHeight)            {                // 开始截取坐标过大时，结束处理                 return null;            }            if (StartX + destWidth > srcWidth)            {                // 宽度过大时只截取到最大大小                 destWidth = srcWidth - StartX;            }            if (StartY + destHeight > srcHeight)            {                // 高度过大时只截取到最大大小                 destHeight = srcHeight - StartY;            }            try            {                // 根据目标图片的大小，实例化一个画布                Bitmap bmpOut = new Bitmap(destWidth, destHeight);                // 实例化一个画笔                Graphics g = Graphics.FromImage(bmpOut);                // 将原始图片画到目标画布上                g.DrawImage(image, new Rectangle(0, 0, destWidth, destHeight), new Rectangle(StartX, StartY, destWidth, destHeight), GraphicsUnit.Pixel);                g.Dispose();                return bmpOut;            }            catch            {                return null;            }        }    }}
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