1. 概述
有时候我们需要在web页面上显示一张图，比如说一张地图，而这张地图会比较大。这时候如果我们把一张大图分隔成一组小图，那么客户端的显示速度会明显地感觉块。希望阅读本文对你有所帮助。
2. 实现思路
.NET Framework GDI+ 为我们提供了一组丰富地类来编辑图形图像。有关.NET Framework GDI+的详细资料请查阅msdn相关文档。这里只简要叙述本程序要用的的几个类。
System.Drawing.Image.LoadFile方法可以从指定的文件创建 Image 对象。System.Drawing.Image.Save方法可以将此 Image 对象保存到指定文件。System.Drawing.Image.Width和System.Drawing.Image.Height属性可以得到图片的宽度和高度。
System.Drawing.Graphics类可以编辑图像。System.Drawing.Graphics.DrawImage方法在指定位置并且按指定大小绘制指定的 Image 对象的指定部分。
图片分隔说明：就是把一张大图，按指定的宽度和高度分隔成一组小图
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| 图1 |
对初学者的提示：在我们读书时学过的数学坐标如图2所示，在GDI＋里的坐标如图3所示
 |  |
| 图2 | 图3 |
3. 实现代码
1
public class CropImageManipulator
2
{
3
public CropImageManipulator()
4
{
5
6
}
7
8 // 不含扩展名的文件名
9 private string _fileNameWithoutExtension;
10 // 文件扩展名
11 private string _fileExtension;
12 // 文件所属的文件夹
13 private string _fileDirectory;
14 public string Cropping(string inputImgPath, int cropWidth, int cropHeight)
15 {
16 this._fileNameWithoutExtension = System.IO.Path.GetFileNameWithoutExtension(inputImgPath);
17 this._fileExtension = System.IO.Path.GetExtension(inputImgPath);
18 this._fileDirectory = System.IO.Path.GetDirectoryName(inputImgPath);
19
20 // 装载要分隔的图片
21 Image inputImg = Image.FromFile(inputImgPath);
22 int imgWidth = inputImg.Width;
23 int imgHeight = inputImg.Height;
24
25 // 计算要分几格
26 int widthCount = (int)Math.Ceiling((imgWidth * 1.00) / (cropWidth * 1.00));
27 int heightCount = (int)Math.Ceiling((imgHeight * 1.00) / (cropHeight * 1.00));
28 //----------------------------------------------------------------------
29 ArrayList areaList = new ArrayList();
30
31 System.Text.StringBuilder sb = new System.Text.StringBuilder();
32 sb.Append("<table cellpadding='0' cellspacing='0' border='[$border]'>");
33 sb.Append(System.Environment.NewLine);
34
35 int i = 0;
36 for (int iHeight = 0; iHeight < heightCount ; iHeight ++)
37 {
38 sb.Append("<tr>");
39 sb.Append(System.Environment.NewLine);
40 for (int iWidth = 0; iWidth < widthCount ; iWidth ++)
41 {
42 //string fileName = "<img src='http://localhost/SRcommBeijingFile/" + this._fileNameWithoutExtension + " _" + i.ToString() + this._fileExtension + "'>";
43 string fileName = string.Format("<img src='http://localhost/SRcommBeijingFile/{0}_{1}{2}' />",this._fileNameWithoutExtension,i,this._fileExtension);
44 sb.Append("<td>" + fileName + "</td>");
45 sb.Append(System.Environment.NewLine);
46
47
48 int pointX = iWidth * cropWidth;
49 int pointY = iHeight * cropHeight;
50 int areaWidth = ((pointX + cropWidth) > imgWidth) ? (imgWidth - pointX) : cropWidth;
51 int areaHeight = ((pointY + cropHeight) > imgHeight) ? (imgHeight - pointY) : cropHeight;
52 string s = string.Format("{0};{1};{2};{3}",pointX,pointY,areaWidth,areaHeight);
53
54 Rectangle rect = new Rectangle(pointX,pointY,areaWidth,areaHeight);
55 areaList.Add(rect);
56 i ++;
57 }
58 sb.Append("</tr>");
59 sb.Append(System.Environment.NewLine);
60 }
61
62 sb.Append("</table>");
63
64
65 //----------------------------------------------------------------------
66
67 for (int iLoop = 0 ; iLoop < areaList.Count ; iLoop ++)
68 {
69 Rectangle rect = (Rectangle)areaList[iLoop];
70 string fileName = this._fileDirectory + "//" + this._fileNameWithoutExtension + "_" + iLoop.ToString() + this._fileExtension;
71 Bitmap newBmp = new Bitmap(rect.Width,rect.Height,PixelFormat.Format24bppRgb);
72 Graphics newBmpGraphics = Graphics.FromImage(newBmp);
73 newBmpGraphics.DrawImage(inputImg,new Rectangle(0,0,rect.Width,rect.Height),rect,GraphicsUnit.Pixel);
74 newBmpGraphics.Save();
75 switch (this._fileExtension.ToLower())
76 {
77 case ".jpg":
78 case ".jpeg":
79 newBmp.Save(fileName,ImageFormat.Jpeg);
80 break;
81 case "gif":
82 newBmp.Save(fileName,ImageFormat.Gif);
83 break;
84 }
85
86 }
87 inputImg.Dispose();
88 string html = sb.ToString();
89 return html;
90 }
91
92
}
public class CropImageManipulator2
{3
public CropImageManipulator()4
{5
6
}7
8
// 不含扩展名的文件名9
private string _fileNameWithoutExtension;10
// 文件扩展名11
private string _fileExtension;12
// 文件所属的文件夹13
private string _fileDirectory;14
public string Cropping(string inputImgPath, int cropWidth, int cropHeight)15
{16
this._fileNameWithoutExtension = System.IO.Path.GetFileNameWithoutExtension(inputImgPath);17
this._fileExtension = System.IO.Path.GetExtension(inputImgPath);18
this._fileDirectory = System.IO.Path.GetDirectoryName(inputImgPath);19
20
// 装载要分隔的图片21
Image inputImg = Image.FromFile(inputImgPath);22
int imgWidth = inputImg.Width;23
int imgHeight = inputImg.Height;24
25
// 计算要分几格26
int widthCount = (int)Math.Ceiling((imgWidth * 1.00) / (cropWidth * 1.00));27
int heightCount = (int)Math.Ceiling((imgHeight * 1.00) / (cropHeight * 1.00));28
//----------------------------------------------------------------------29
ArrayList areaList = new ArrayList();30
31
System.Text.StringBuilder sb = new System.Text.StringBuilder();32
sb.Append("<table cellpadding='0' cellspacing='0' border='[$border]'>");33
sb.Append(System.Environment.NewLine);34
35
int i = 0;36
for (int iHeight = 0; iHeight < heightCount ; iHeight ++)37
{38
sb.Append("<tr>");39
sb.Append(System.Environment.NewLine);40
for (int iWidth = 0; iWidth < widthCount ; iWidth ++)41
{42
//string fileName = "<img src='http://localhost/SRcommBeijingFile/" + this._fileNameWithoutExtension + " _" + i.ToString() + this._fileExtension + "'>";43
string fileName = string.Format("<img src='http://localhost/SRcommBeijingFile/{0}_{1}{2}' />",this._fileNameWithoutExtension,i,this._fileExtension);44
sb.Append("<td>" + fileName + "</td>");45
sb.Append(System.Environment.NewLine);46
47
48
int pointX = iWidth * cropWidth;49
int pointY = iHeight * cropHeight;50
int areaWidth = ((pointX + cropWidth) > imgWidth) ? (imgWidth - pointX) : cropWidth;51
int areaHeight = ((pointY + cropHeight) > imgHeight) ? (imgHeight - pointY) : cropHeight;52
string s = string.Format("{0};{1};{2};{3}",pointX,pointY,areaWidth,areaHeight);53
54
Rectangle rect = new Rectangle(pointX,pointY,areaWidth,areaHeight);55
areaList.Add(rect);56
i ++;57
}58
sb.Append("</tr>");59
sb.Append(System.Environment.NewLine);60
}61
62
sb.Append("</table>");63
64
65
//---------------------------------------------------------------------- 66
67
for (int iLoop = 0 ; iLoop < areaList.Count ; iLoop ++)68
{69
Rectangle rect = (Rectangle)areaList[iLoop];70
string fileName = this._fileDirectory + "//" + this._fileNameWithoutExtension + "_" + iLoop.ToString() + this._fileExtension;71
Bitmap newBmp = new Bitmap(rect.Width,rect.Height,PixelFormat.Format24bppRgb);72
Graphics newBmpGraphics = Graphics.FromImage(newBmp);73
newBmpGraphics.DrawImage(inputImg,new Rectangle(0,0,rect.Width,rect.Height),rect,GraphicsUnit.Pixel);74
newBmpGraphics.Save();75
switch (this._fileExtension.ToLower())76
{77
case ".jpg":78
case ".jpeg":79
newBmp.Save(fileName,ImageFormat.Jpeg);80
break;81
case "gif":82
newBmp.Save(fileName,ImageFormat.Gif);83
break;84
}85
86
}87
inputImg.Dispose();88
string html = sb.ToString();89
return html;90
}91
92
}
)
 ---C++17 并发编程)
