• C# 图片超过指定大小将压缩到指定大小不失真


    using System;
    using System.Collections.Generic;
    using System.Drawing;
    using System.Drawing.Drawing2D;
    using System.Linq;
    using System.Web;

    namespace Book_Painting.Common
    {
    /// <summary>
    /// 图片压缩
    /// </summary>
    public class ThumbnailImage
    {
    /// <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="srcImage"></param>
    /// <param name="iWidth"></param>
    /// <param name="iHeight"></param>
    /// <returns></returns>
    public Bitmap SizeImageWithOldPercent(Image srcImage, int iWidth, int iHeight)
    {
    try
    {
    // 要截取图片的宽度(临时图片)
    int newW = srcImage.Width;
    // 要截取图片的高度(临时图片)
    int newH = srcImage.Height;
    // 截取开始横坐标(临时图片)
    int newX = 0;
    // 截取开始纵坐标(临时图片)
    int newY = 0;
    // 截取比例(临时图片)
    double whPercent = 1;
    whPercent = ((double)iWidth / (double)iHeight) * ((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
    newW = 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
    newH = int.Parse(Math.Round(srcImage.Height * whPercent).ToString());
    }
    if (newW != 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 - newW) / 2).ToString()));
    }
    else if (newH == 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)newH) / 2).ToString()));
    }
    // 取得符合比例的临时文件
    Bitmap cutedImage = CutImage(srcImage, newX, newY, newW, newH);
    // 保存到的文件
    Bitmap b = new Bitmap(iWidth, iHeight);
    Graphics g = Graphics.FromImage(b);
    // 插值算法的质量
    g.InterpolationMode = InterpolationMode.Default;
    g.DrawImage(cutedImage, new Rectangle(0, 0, iWidth, iHeight), new Rectangle(0, 0, cutedImage.Width, cutedImage.Height), GraphicsUnit.Pixel);
    g.Dispose();
    return b;
    }
    catch (Exception)
    {
    return null;
    }
    }

    /// <summary>
    /// 剪裁 -- 用GDI+
    /// </summary>
    /// <param name="b">原始Bitmap</param>
    /// <param name="StartX">开始坐标X</param>
    /// <param name="StartY">开始坐标Y</param>
    /// <param name="iWidth">宽度</param>
    /// <param name="iHeight">高度</param>
    /// <returns>剪裁后的Bitmap</returns>
    public Bitmap CutImage(Image b, int StartX, int StartY, int iWidth, int iHeight)
    {
    if (b == null)
    {
    return null;
    }
    int w = b.Width;
    int h = b.Height;
    if (StartX >= w || StartY >= h)
    {
    // 开始截取坐标过大时,结束处理
    return null;
    }
    if (StartX + iWidth > w)
    {
    // 宽度过大时只截取到最大大小
    iWidth = w - StartX;
    }
    if (StartY + iHeight > h)
    {
    // 高度过大时只截取到最大大小
    iHeight = h - StartY;
    }
    try
    {
    Bitmap bmpOut = new Bitmap(iWidth, iHeight);
    Graphics g = Graphics.FromImage(bmpOut);
    g.DrawImage(b, new Rectangle(0, 0, iWidth, iHeight), new Rectangle(StartX, StartY, iWidth, iHeight), GraphicsUnit.Pixel);
    g.Dispose();
    return bmpOut;
    }
    catch
    {
    return null;
    }
    }

    }
    }

    调用截图

     

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  • 原文地址:https://www.cnblogs.com/louby/p/4794330.html
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