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[ASP.net教程]图片缩放的相关处理


图片缩放的相关处理

最近自己做的点东西上用到了图片的处理,不过没有找到合适的图片处理相关算法,倒是找到了几个获取缩略图的算法。代码不长,简单看了看原理也比较简单(其实不是简单是C#的封装的太多了,所以显得比较简单)。既然没有相关的统一调用的代码,索性,我来整理一套相关的处理代码然后公开出来吧。

图片处理的相关分析

其实我要用的图片处理非常简单,就是简单的压缩一下图片。然后把图片设置到对应大小而已。但是对于设置的方式,C#基础的函数中使用的Rect范围设置。这个范围设置计算起来可能相对头疼一些。所以我在考虑要不要让调用者在忽略Rect这个参数的情况愉快的调用接口呢?于是乎,我定义了几个图片缩放类型(Full、Zoom、Overflow、Original)。然后默认的让原始图片的中心点与输出图片的中心点对齐。然后根据缩放类型来对图片进行不同的缩放模式。

缩放模式

  1. Full:让图片放弃原来的比例,直接按照目标数据进行拉伸
  2. Zoom:让图片保持原有比例,并且保证原始图片在目标图片的正中央,没有图片的位置保留米白色
  3. Original:让图片保持原来的大小,输出图片类似于裁剪中间位置某个范围的图片
  4. Overflow:让图片保持原来的比例,并且保证输目标是被图片填满的不留空白

调用的范例

ImageHelper.GetInstance().ImageCompress(InputFile, Path.Combine(OutPutPath, item_file), new System.Drawing.Size(500, 300), ImageZoomType.Full, 50);

样品展示

原始图片

Full 300*500 

 

Full 500 * 300

 

Original 300 * 500

 

Original 500 * 300

 

Overflow 300 * 500

 

Overflow 500 * 300

 

Zoom 300 * 500

 

Zoom 500 * 300

存在的不足

  1. 压缩没有独到的技术
  2. 目前只支持JPEG格式的图片
  3. 部分图片进行缩放之后会留下一个1像素浅浅的边

后续的内容

图片处理不光是缩放,还有其他的很多东西比较实用(截图、压缩、按高缩放、按宽缩放、添加水印、添加隐藏水印),我准备把图片常用的相关处理。整理成一个帮助类,方便迁入到各个项目中去。

所以我建立了一个专门的图片处理的开源项目方便后续功能加入,地址如下:http://git.oschina.net/anxin1225/ImageCompress

 

压缩相关的代码

using System;using System.Collections.Generic;using System.Drawing;using System.Drawing.Drawing2D;using System.Drawing.Imaging;using System.IO;using System.Linq;using System.Text;using System.Threading.Tasks;namespace ImageCompress{  public struct AnchorPoint  {    //public AnchorPoint() : this(0, 0) { }    public AnchorPoint(double x, double y)    {      X = x;      Y = y;    }    public double X, Y;  }  public enum ImageZoomType  {    Full,    Zoom,    Overflow,    Original,  }  public delegate void ImageHandle(Image image, Bitmap bitmap);  public class ImageHelper  {    private ImageHelper() { }    private static ImageHelper _image_helper = null;    private Dictionary<ImageZoomType, ImageHandle> _name_to_handle = new Dictionary<ImageZoomType, ImageHandle>();    public static ImageHelper GetInstance()    {      if (_image_helper == null)      {        _image_helper = new ImageHelper();        //填满        _image_helper._name_to_handle[ImageZoomType.Full] = (image, bitmap) =>        {          _image_helper.DrawImage(image, bitmap, new Rectangle(new Point(0, 0), bitmap.Size));        };        //原始        _image_helper._name_to_handle[ImageZoomType.Original] = (image, bitmap) =>        {          _image_helper.DrawImage(image, bitmap, 1, new AnchorPoint(0.5, 0.5), new AnchorPoint(0.5, 0.5));        };        //溢出        _image_helper._name_to_handle[ImageZoomType.Overflow] = (image, bitmap) =>        {          float proportion_x = (float)bitmap.Width / image.Width;          float proportion_y = (float)bitmap.Height / image.Height;          _image_helper.DrawImage(image, bitmap, proportion_x > proportion_y ? proportion_x : proportion_y, new AnchorPoint(0.5, 0.5), new AnchorPoint(0.5, 0.5));        };        //缩放        _image_helper._name_to_handle[ImageZoomType.Zoom] = (image, bitmap) =>        {          float proportion_x = (float)bitmap.Width / image.Width;          float proportion_y = (float)bitmap.Height / image.Height;          _image_helper.DrawImage(image, bitmap, proportion_x < proportion_y ? proportion_x : proportion_y, new AnchorPoint(0.5, 0.5), new AnchorPoint(0.5, 0.5));        };      }      return _image_helper;    }    /// <summary>    /// 压缩图片    /// </summary>    /// <param name="source_path">源数据位置</param>    /// <param name="save_path">保存数据位置</param>    /// <param name="save_size">保存图片大小</param>    /// <param name="ztype">缩放模式</param>    /// <param name="flag">图片保存品质</param>    /// <returns>是否完成压缩</returns>    public bool ImageCompress(string source_path, string save_path, Size save_size, ImageZoomType ztype, int flag)    {      bool success = false;      Image source = null;      while (true)      {        source = LoadImage(source_path);        if (source == null)          break;        Bitmap bitmap = new Bitmap(save_size.Width, save_size.Height);        if (_name_to_handle.ContainsKey(ztype))        {          _name_to_handle[ztype](source, bitmap);        }        else        {          break;        }        success = SaveImage(bitmap, save_path, source.RawFormat, flag);        break;      }      if (source != null)        source.Dispose();      return success;    }    public Image LoadImage(string source_path)    {      Image image = null;      while (true)      {        if (!File.Exists(source_path))          break;        try        {          image = Image.FromFile(source_path);        }        catch        {          break;        }        break;      }      return image;    }    /// <summary>    /// 将BitMap保存到磁盘上    /// </summary>    /// <param name="image">需要保存的图片</param>    /// <param name="save_path">保存的路径</param>    /// <param name="format">保存格式</param>    /// <param name="flag">保存质量</param>    /// <returns></returns>    public bool SaveImage(Bitmap image, string save_path, ImageFormat format, int flag)    {      //以下代码为保存图片时,设置压缩质量       EncoderParameters ep = new EncoderParameters();      long[] qy = new long[1];      qy[0] = flag;//设置压缩的比例1-100       EncoderParameter eParam = new EncoderParameter(System.Drawing.Imaging.Encoder.Quality, qy);      ep.Param[0] = eParam;      try      {        ImageCodecInfo[] arrayICI = ImageCodecInfo.GetImageEncoders();        ImageCodecInfo jpegICIinfo = null;        for (int x = 0; x < arrayICI.Length; x++)        {          if (arrayICI[x].FormatDescription.Equals("JPEG"))          {            jpegICIinfo = arrayICI[x];            break;          }        }        if (jpegICIinfo != null)        {          image.Save(save_path, jpegICIinfo, ep);//dFile是压缩后的新路径         }        else        {          image.Save(save_path, format);        }        return true;      }      catch      {        return false;      }      finally      {        image.Dispose();      }    }    /// <summary>    /// 画图    /// </summary>    /// <param name="source">原始图像</param>    /// <param name="output">输出图像</param>    /// <param name="souce_scale">原始图像的缩放值</param>    /// <param name="souce_anchor"></param>    /// <param name="graphics_anchor"></param>    public void DrawImage(Image source, Bitmap output, float souce_scale, AnchorPoint souce_anchor, AnchorPoint graphics_anchor)    {      DrawImage(source, output, souce_scale, souce_anchor, new Point((int)(output.Width * graphics_anchor.X), (int)(output.Height * graphics_anchor.Y)));    }    /// <summary>    /// 画图    /// </summary>    /// <param name="source">原始图像</param>    /// <param name="output">输出凸显</param>    /// <param name="source_scale">图像的所放值</param>    /// <param name="source_anchor">源图像锚点</param>    /// <param name="souce_point">图像位置</param>    public void DrawImage(Image source, Bitmap output, float source_scale, AnchorPoint source_anchor, Point souce_point)    {      var pic_po = new Point((int)(souce_point.X - source.Size.Width * source_scale * source_anchor.X), (int)(souce_point.Y - source.Size.Height * source_scale * source_anchor.Y));      DrawImage(source, output, new Rectangle(pic_po, new Size((int)(source.Width * source_scale), (int)(source.Height * source_scale))));    }    /// <summary>    /// 画图    /// </summary>    /// <param name="source"></param>    /// <param name="output"></param>    /// <param name="rect"></param>    public void DrawImage(Image source, Bitmap output, Rectangle rect)    {      Graphics g = Graphics.FromImage(output);      g.Clear(Color.WhiteSmoke);      g.CompositingQuality = CompositingQuality.HighQuality;      g.SmoothingMode = SmoothingMode.HighQuality;      g.InterpolationMode = InterpolationMode.HighQualityBicubic;      g.DrawImage(source, rect, 0, 0, source.Width, source.Height, GraphicsUnit.Pixel);      g.Dispose();    }  }}

  

 

PS:为了美观本文中的原始图片并不是原始图片,因为原始图片太大了。会造成页面滑动,所以我上传了一张较小的图片。Git的图片则是原始的图片