做项目时发现客户有时传的好多海报大图，前台展示轮播几十张会加载很慢，以前只用过php的timthumb，这就自己写了一个asp.net版的使用
调用方式和他类似，
Original：1 or 0是否为返回原图Url
Compress压缩比0-100 100最好
例如：http://yourServer/handlers/thumb.ashx?ImgUrl=/Upload/Poster/20171205/17120511041625.jpg&Width=185&Height=300&Compress=70&Original=
会直接返回图片数据写入到页面内，而且简单做了下缓存处理，就是如果同一个地址同一个宽高的图片，每次处理前会先判断是否已经处理过，如果已经处理过直接找到那个图片返回去就行，省的每次都处理，文件越来越多。
namespace WebApplication.Handlers
{
/// <summary>
/// 裁剪压缩图片
/// </summary>
public class Thumb : IHttpHandler
{
public string SavePath = "/Upload";
public string ThumbImageDir = "Thumb";
public void ProcessRequest(HttpContext context)
{
string err = string.Empty;
string original = GetRequestValue("Original"); //返回原图URL 1 0
string imgUrl = GetRequestValue("ImgUrl");
string width = GetRequestValue("Width");
string height = GetRequestValue("Height");
string compress = GetRequestValue("Compress");//压缩比、1-100
if (StrEmpty(imgUrl))
err += " Image url error";
if (StrEmpty(width))
err += " Please enter image width";
if (StrEmpty(height))
err += " Please enter image height";
if (!StrEmpty(err))
{
context.Response.Write(err);
context.Response.End();
}
//视情况而定，如果是图片完整路径就直接imgUrl就好 此项目中都是相对路径
imgUrl = "http://" + context.Request.Url.Authority + imgUrl;
string imgMd5 = GetFileSaveName(imgUrl + "_" + width + "x" + height); //保存的文件名Url的MD5加上宽x高
string fileExt = Path.GetExtension(imgUrl);
//返回原图地址
if (string.Compare(original, "1") == 0)
{
context.Response.Write(imgUrl);
context.Response.End();
}
context.Response.ContentType = "image/png";
string thumbImgPath = SavePath + "/" + ThumbImageDir + "/" + imgMd5 + "_thumb" + fileExt; //压缩后的图片路径
string strResizeImgPath = HttpContext.Current.Server.MapPath(thumbImgPath);
string serverThumbImgDir = HttpContext.Current.Server.MapPath(SavePath + "/" + ThumbImageDir);
if (!Directory.Exists(serverThumbImgDir))
Directory.CreateDirectory(serverThumbImgDir);
//如果缩略图已经存在 l
if (File.Exists(HttpContext.Current.Server.MapPath(thumbImgPath)))
{
WriteImg(strResizeImgPath);
}
Stream imgSavePath = HttpDownloadFile(imgUrl);
if (imgSavePath == null)
{
err += " Image url error";
context.Response.Write(err);
context.Response.End();
}
bool flag = false;
Image thumbImg = Image.FromStream(imgSavePath);
int imgWidth = thumbImg.Width;
int imgHeight = thumbImg.Height;
int maxWidth = Convert.ToInt32(width);
int maxHeight = Convert.ToInt32(height);
if (imgWidth > imgHeight) //如果宽度超过高度以宽度为准来调整
{
if (imgWidth > maxWidth) //如果图片宽度超过限制
{
int toImgWidth = maxWidth; //图片调整后的宽度
int toImgHeight = imgHeight / (int)(imgWidth / toImgWidth); //图片调整后的高度
Bitmap img = new Bitmap(thumbImg, int.Parse(toImgWidth.ToString()), int.Parse(toImgHeight.ToString()));
if (StrEmpty(compress)) img.Save(strResizeImgPath); //保存调整大小后的图片
else
Compress(img, strResizeImgPath, Convert.ToInt32(compress)); //压缩
flag = true;
}
}
else
{
if (imgHeight > maxHeight)
{
int toImgHeight = maxHeight;
int toImgWidth = imgWidth / (int)(imgHeight / toImgHeight);
Bitmap img = new Bitmap(thumbImg, int.Parse(toImgWidth.ToString()), int.Parse(toImgHeight.ToString()));
if (StrEmpty(compress)) img.Save(strResizeImgPath); //保存调整大小后的图片
else
Compress(img, strResizeImgPath, Convert.ToInt32(compress)); //压缩
flag = true;
}
}
if (flag)
{
WriteImg(strResizeImgPath);
}
else
context.Response.Write("Resize Faild");
}
public void WriteImg(string imgPath)
{
var imgStream = new FileStream(imgPath, FileMode.Open);
byte[] byteImg = new byte[imgStream.Length];
imgStream.Read(byteImg, 0, byteImg.Length);
imgStream.Close();
HttpContext.Current.Response.OutputStream.Write(byteImg, 0, byteImg.Length);
HttpContext.Current.Response.End();
}
/// <summary>
/// 获取缩略图文件保存的文件名
/// </summary>
/// <param name="url">图片URL</param>
/// <returns></returns>
public string GetFileSaveName(string url)
{
return System.Web.Security.FormsAuthentication.HashPasswordForStoringInConfigFile(url, "MD5");
}
/// <summary>
/// 获取文件MD5值
/// </summary>
/// <param name="fileStream"></param>
/// <returns></returns>
public string GetFileMd5(Stream fileStream)
{
MD5 md5 = new MD5CryptoServiceProvider();
byte[] retVal = md5.ComputeHash(fileStream);
StringBuilder sb = new StringBuilder();
for (int i = 0; i < retVal.Length; i++)
{
sb.Append(retVal[i].ToString("x2"));
}
return sb.ToString();
}
/// <summary>
/// 下载URL文件 返回Stream
/// </summary>
/// <param name="url">文件URL</param>
/// <returns></returns>
public Stream HttpDownloadFile(string url)
{
if (!url.Contains("http://") && !url.Contains("https://"))
{
url = "http://" + url;
}
try
{
HttpWebRequest myRequest = (HttpWebRequest)WebRequest.Create(url);
myRequest.Timeout = 10000; //超时时间10秒
HttpWebResponse res = (HttpWebResponse)myRequest.GetResponse();
if (res.StatusCode == HttpStatusCode.OK)
{
Stream responseStream = res.GetResponseStream();
MemoryStream ms = new MemoryStream();
byte[] bArr = new byte[1024];
int size = responseStream.Read(bArr, 0, (int)bArr.Length);
while (size > 0)
{
ms.Write(bArr, 0, size);
size = responseStream.Read(bArr, 0, (int)bArr.Length);
}
return ms;
}
else
return null;
}
catch
{
return null;
}
}
private ImageCodecInfo GetEncoderInfo(String mimeType)
{
int j;
ImageCodecInfo[] encoders;
encoders = ImageCodecInfo.GetImageEncoders();
for (j = 0; j < encoders.Length; ++j)
{
if (encoders[j].MimeType == mimeType)
return encoders[j];
}
return null;
}
/// <summary>
/// 图片压缩(降低质量以减小文件的大小)
/// </summary>
/// <param name="srcBitmap">传入的Bitmap对象</param>
/// <param name="destStream">压缩后的Stream对象</param>
/// <param name="level">压缩等级，0到100，0 最差质量，100 最佳</param>
public void Compress(Bitmap srcBitmap, Stream destStream, long level)
{
System.Drawing.Imaging.ImageCodecInfo myImageCodecInfo;
System.Drawing.Imaging.Encoder myEncoder;
EncoderParameter myEncoderParameter;
EncoderParameters myEncoderParameters;
// Get an ImageCodecInfo object that represents the JPEG codec.
myImageCodecInfo = GetEncoderInfo("image/jpeg");
// Create an Encoder object based on the GUID
// for the Quality parameter category.
myEncoder = System.Drawing.Imaging.Encoder.Quality;
// Create an EncoderParameters object.
// An EncoderParameters object has an array of EncoderParameter
// objects. In this case, there is only one
// EncoderParameter object in the array.
myEncoderParameters = new EncoderParameters(1);
// Save the bitmap as a JPEG file with 给定的 quality level
myEncoderParameter = new EncoderParameter(myEncoder, level);
myEncoderParameters.Param[0] = myEncoderParameter;
srcBitmap.Save(destStream, myImageCodecInfo, myEncoderParameters);
}
/// <summary>
/// 图片压缩(降低质量以减小文件的大小)
/// </summary>
/// <param name="srcBitMap">传入的Bitmap对象</param>
/// <param name="destFile">压缩后的图片保存路径</param>
/// <param name="level">压缩等级，0到100，0 最差质量，100 最佳</param>
public void Compress(Bitmap srcBitMap, string destFile, long level)
{
Stream s = new FileStream(destFile, FileMode.Create);
Compress(srcBitMap, s, level);
s.Close();
}
public string GetRequestValue(string key)
{
try
{
return HttpContext.Current.Request[key].ToString();
}
catch (global::System.Exception)
{
return string.Empty;
}
}
#region 字母随机数
/// <summary>
/// 字母随机数
/// </summary>
/// <param name="n">生成长度</param>
/// <returns></returns>
public static string RandLetter(int n)
{
char[] arrChar = new char[]{
'a','b','d','c','e','f','g','h','i','j','k','l','m','n','p','r','q','s','t','u','v','w','z','y','x',
'_',
'A','B','C','D','E','F','G','H','I','J','K','L','M','N','Q','P','R','T','S','V','U','W','X','Y','Z'
};
StringBuilder num = new StringBuilder();
Random rnd = new Random(DateTime.Now.Millisecond);
for (int i = 0; i < n; i++)
{
num.Append(arrChar[rnd.Next(0, arrChar.Length)].ToString());
}
return num.ToString();
}
#endregion
/// <summary>
/// 字符串是否为空
/// </summary>
/// <param name="str"></param>
/// <returns></returns>
public bool StrEmpty(string str)
{
return string.IsNullOrEmpty(str);
}
public bool IsReusable
{
get
{
return false;
}
}
}
}
