圖片縮放的相關處理
最近自己做的點東西上用到了圖片的處理，不過沒有找到合適的圖片處理相關算法，倒是找到了幾個獲取縮略圖的算法。代碼不長，簡單看了看原理也比較簡單（其實不是簡單是C#的封裝的太多了，所以顯得比較簡單）。既然沒有相關的統一調用的代碼，索性，我來整理一套相關的處理代碼然後公開出來吧。
圖片處理的相關分析
其實我要用的圖片處理非常簡單，就是簡單的壓縮一下圖片。然後把圖片設置到對應大小而已。但是對於設置的方式，C#基礎的函數中使用的Rect范圍設置。這個范圍設置計算起來可能相對頭疼一些。所以我在考慮要不要讓調用者在忽略Rect這個參數的情況愉快的調用接口呢？於是乎，我定義了幾個圖片縮放類型（Full、Zoom、Overflow、Original）。然後默認的讓原始圖片的中心點與輸出圖片的中心點對齊。然後根據縮放類型來對圖片進行不同的縮放模式。
縮放模式
調用的范例
ImageHelper.GetInstance().ImageCompress(InputFile, Path.Combine(OutPutPath, item_file), new System.Drawing.Size(500, 300), ImageZoomType.Full, 50);
樣品展示
原始圖片
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
後續的內容
圖片處理不光是縮放，還有其他的很多東西比較實用（截圖、壓縮、按高縮放、按寬縮放、添加水印、添加隱藏水印），我准備把圖片常用的相關處理。整理成一個幫助類，方便遷入到各個項目中去。
所以我建立了一個專門的圖片處理的開源項目方便後續功能加入，地址如下：http://git.oschina.net/anxin1225/ImageCompress
壓縮相關的代碼
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();
//填滿
_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));
};
//縮放
_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>
/// 壓縮圖片
/// </summary>
/// <param name="source_path">源數據位置</param>
/// <param name="save_path">保存數據位置</param>
/// <param name="save_size">保存圖片大小</param>
/// <param name="ztype">縮放模式</param>
/// <param name="flag">圖片保存品質</param>
/// <returns>是否完成壓縮</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>
/// 將BitMap保存到磁盤上
/// </summary>
/// <param name="image">需要保存的圖片</param>
/// <param name="save_path">保存的路徑</param>
/// <param name="format">保存格式</param>
/// <param name="flag">保存質量</param>
/// <returns></returns>
public bool SaveImage(Bitmap image, string save_path, ImageFormat format, int flag)
{
//以下代碼為保存圖片時，設置壓縮質量
EncoderParameters ep = new EncoderParameters();
long[] qy = new long[1];
qy[0] = flag;//設置壓縮的比例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是壓縮後的新路徑
}
else
{
image.Save(save_path, format);
}
return true;
}
catch
{
return false;
}
finally
{
image.Dispose();
}
}
/// <summary>
/// 畫圖
/// </summary>
/// <param name="source">原始圖像</param>
/// <param name="output">輸出圖像</param>
/// <param name="souce_scale">原始圖像的縮放值</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>
/// 畫圖
/// </summary>
/// <param name="source">原始圖像</param>
/// <param name="output">輸出凸顯</param>
/// <param name="source_scale">圖像的所放值</param>
/// <param name="source_anchor">源圖像錨點</param>
/// <param name="souce_point">圖像位置</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>
/// 畫圖
/// </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：為了美觀本文中的原始圖片並不是原始圖片，因為原始圖片太大了。會造成頁面滑動，所以我上傳了一張較小的圖片。Git的圖片則是原始的圖片
