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我做了图像重新大小处理程序。我得到这个例外。我得到这个异常“参数无效.at System.Drawing.Bitmap..ctor（Int32宽度，Int32高度，PixelFormat格式）”
“HttpApplication.ExecuteStep => CallHandlerExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute => ImageHandler.ProcessRequest | System.ArgumentException：在System.Drawing.Bitmap..ctor参数无效。 （Int32宽度，Int32 高度，PixelFormat格式）在 Holmgrens.ImageResize.IMGHandller.ImageHandler.ProcessRequest（HttpContext 上下文）“。
这是我的代码。
using System;
using System.Collections.Generic;
using System.Text;
using System.Web;
using System.Drawing;
using System.IO;
namespace Xyz.ImageResize.IMGHandller
{
public class ImageHandler : IHttpHandler
{
// incoming query string variables
private string imagePath = string.Empty; // path= virtual path required
private string imageWidth = "0"; // w= 0 means use original
private string imageHeight = "0"; // h=
private string imageQuality = "0"; // q=
private string constrainProportions = "true"; // cp= true or false
private string rotation = "0"; // r= rotation in degrees, optional, 0 is default.
private const Int32 maxQuality = 100;
private const Int32 minQuality = 30;
private const string imageNotFound = "~/SlideData/TempImg/Desert.jpg";
private string mimeType = "image/jpeg";
//get imag config item
//ImageConfiguration imgconsetting = new ImageConfiguration();
public void ProcessRequest(HttpContext context)
{
try
{
// get query string parameters
imagePath = context.Request.QueryString["path"];
imageWidth = context.Request.QueryString["w"];
imageHeight = context.Request.QueryString["h"];
imageQuality = context.Request.QueryString["q"];
constrainProportions = context.Request.QueryString["cp"];
rotation = context.Request.QueryString["r"];
if (System.IO.File.Exists(HttpContext.Current.Server.MapPath(imagePath)))
{
imagePath = HttpContext.Current.Server.MapPath(imagePath);
}
else
{
// displays an empty image holder or make sure you have a not found image
imageQuality = "100";
imagePath = HttpContext.Current.Server.MapPath(imageNotFound);
}
//get file info
FileInfo fi = new FileInfo(imagePath);
if (fi.Extension.ToLower() == ".gif")
mimeType = "image/gif";
else if (fi.Extension.ToLower() == ".png")
mimeType = "image/png";
else
mimeType = "image/jpeg";
// sets the HTTP MIME type of the output stream.
// jpeg is default
context.Response.ContentType = mimeType;
// clear all content output from the buffer stream
context.Response.Clear();
// response is cacheable by clients and shared (proxy) caches
context.Response.Expires = 24 * 60; //one day;
string ETag = Hash.GetHash(string.Format("{0}{1}", imagePath, fi.LastWriteTimeUtc.ToString()), Hash.HashType.MD5);
context.Response.Cache.SetCacheability(HttpCacheability.Public);
context.Response.Cache.SetLastModified(fi.LastWriteTimeUtc);
context.Response.Cache.SetETag(string.Format("\"{0}\"", ETag));
// Buffer response so that page is sent
// after processing is complete.
context.Response.BufferOutput = true;
//if image height is zero,calculate the image height with aspect ration of image
if (imageHeight == "0")
{
imageHeight = ImageHeightWithAspect(imagePath, Convert.ToInt16(imageWidth)).ToString();
}
Int32 originalWidth = 0;
Int32 originalHeight = 0;
Int32 newWidth = 0;
Int32 newHeight = 0;
Int64 quality = 0;
// set the quality of the jpeg image returned.. 30 (low) - 100 (high)
if (Int64.TryParse(imageQuality, out quality))
{
if (quality > maxQuality) { quality = maxQuality; }
if (quality < minQuality) { quality = minQuality; }
}
else
{ quality = maxQuality; }
// ENCODING
System.Drawing.Imaging.Encoder encoder =
System.Drawing.Imaging.Encoder.Quality;
System.Drawing.Imaging.EncoderParameter encoderParameter =
new System.Drawing.Imaging.EncoderParameter(encoder, quality);
// create an array with one parameter; quality
System.Drawing.Imaging.EncoderParameters codecParams =
new System.Drawing.Imaging.EncoderParameters(1);
codecParams.Param[0] = encoderParameter;
// Gets the codecs for this image type (jpeg)
System.Drawing.Imaging.ImageCodecInfo codecInfo = getEncoderInfo();
// Create a bitmap to hold new image, uses Bitmap.GetThumbnailImage
using (System.Drawing.Bitmap bitmapOriginal = new System.Drawing.Bitmap(imagePath))
{
originalWidth = bitmapOriginal.Width;
originalHeight = bitmapOriginal.Height;
Int32.TryParse(imageWidth, out newWidth);
Int32.TryParse(imageHeight, out newHeight);
if (newWidth > originalWidth) { newWidth = originalWidth; }
if (newHeight > originalHeight) { newHeight = originalHeight; }
// Constrain Proportions provides scaling by width
// False by default which forces width and height - when exact size required
if (!string.IsNullOrEmpty(constrainProportions)
&& constrainProportions.Equals("true", StringComparison.OrdinalIgnoreCase))
{
newWidth = Convert.ToInt32(imageWidth);
Double scaleFactor = 0.0;
// scale the image based on the width
if (originalWidth > originalHeight)
{
// landscape
Int32 largestDimension = (Math.Max(originalWidth, originalHeight));
scaleFactor = ((Double)newWidth/(Double)largestDimension);
}
else
{
// portrait
Int32 smallestDimension = (Math.Min(originalWidth, originalHeight));
scaleFactor = ((Double)newWidth/(Double)smallestDimension);
}
newHeight = Convert.ToInt32((originalHeight * scaleFactor));
}
// Create the new bitmap image
using (System.Drawing.Bitmap bitmapNew = new System.Drawing.Bitmap(newWidth, newHeight, System.Drawing.Imaging.PixelFormat.Format24bppRgb))
{
// use the same resolution
bitmapNew.SetResolution(bitmapOriginal.HorizontalResolution, bitmapOriginal.VerticalResolution);
// Create the graphics object to draw the old bitmap on the new sized bitmap.
using (System.Drawing.Graphics graphic = System.Drawing.Graphics.FromImage(bitmapNew))
{
// resize using the highest possible quality for best results
graphic.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.HighQualityBicubic;
graphic.DrawImage(bitmapOriginal,
new System.Drawing.Rectangle(-1, -1, newWidth + 1, newHeight + 1), // destination
new System.Drawing.Rectangle(0, 0, originalWidth, originalHeight), //source
System.Drawing.GraphicsUnit.Pixel); //using pixels
graphic.Dispose();
}
// Rotate the bitmap
switch (Convert.ToInt32(rotation))
{
case 90:
bitmapNew.RotateFlip(System.Drawing.RotateFlipType.Rotate90FlipNone);
break;
case 180:
bitmapNew.RotateFlip(System.Drawing.RotateFlipType.Rotate180FlipNone);
break;
case 270:
bitmapNew.RotateFlip(System.Drawing.RotateFlipType.Rotate270FlipNone);
break;
default:
// always show as original
bitmapNew.RotateFlip(System.Drawing.RotateFlipType.RotateNoneFlipNone);
break;
}
// context.Response.OutputStream enables binary output to the outgoing HTTP content body.
// codecInfo is the image type (jpeg)
// codecParams is the quality
Bitmap bm = new Bitmap(bitmapNew);
bitmapNew.Dispose();
//bm.Save(context.Response.OutputStream, codecInfo, codecParams);
//bm.Dispose();
using (MemoryStream stream = new MemoryStream())
{
bm.Save(stream, codecInfo, codecParams);
stream.WriteTo(context.Response.OutputStream);
stream.Dispose();
}
bm.Dispose();
}
bitmapOriginal.Dispose();
}
encoderParameter.Dispose();
codecParams.Dispose();
}
catch(Exception ex)
{
response.write(ex);
}
}
/// <summary>
/// Return the codec info for jpeg images
/// </summary>
/// <param name="mimeType"></param>
/// <returns></returns>
private System.Drawing.Imaging.ImageCodecInfo getEncoderInfo()
{
System.Drawing.Imaging.ImageCodecInfo[] encoders;
encoders = System.Drawing.Imaging.ImageCodecInfo.GetImageEncoders();
Int32 i = 0;
while (i < encoders.Length)
{
if (encoders[i].MimeType == mimeType)
{
return encoders[i];
}
i++;
}
return null;
}
public bool IsReusable
{ get { return true; } }
private int ImageHeightWithAspect(string fileName,int newWidth)
{
Image original = Image.FromFile(fileName);
//Find the aspect ratio between the height and width.
float aspect = (float)original.Height/(float)original.Width;
//Calculate the new height using the aspect ratio
// and the desired new width.
int newHeight = (int)(newWidth * aspect);
//Dispose of our objects.
original.Dispose();
return newHeight;
}
}
}
请指导我如何删除此例外。
感谢 Humayoo
什么是高度和宽度值，可能类似于[位图参数无效 - 参数异常]（http://stackoverflow.com/questions/5801652/bitmap-while-assigning-height-width-crashes/ 5802113＃5802113） – V4Vendetta