asp.net-core - 在 ASP.NET-Core 2.2 中调整大小和创建图像缩略图
问题描述
我正在尝试在 asp.net-core 2.2 应用程序中创建缩略图图像,但每当它达到创建缩略图的程度时,我都会不断收到上述错误。
主图像可以正常创建和存储,但无法创建缩略图。请感谢任何解决错误的指南
这是我存储上传图像的方法。这个按预期工作
using LazZiya.ImageResize;
using Microsoft.AspNetCore.Hosting;
using Microsoft.AspNetCore.Http;
using System;
using System.Collections.Generic;
using System.Drawing;
using System.IO;
using System.Linq;
using System.Threading.Tasks;
namespace eSchool.Models.Utilities
{
public class FileUploadHelper
{
private readonly IHostingEnvironment host;
public FileUploadHelper(IHostingEnvironment _host)
{
host = _host;
}
public async Task<string> SaveFileAsync(IFormFile file, string pathToUplaod)
{
string webroot=host.WebRootPath;
string DesiredDirectoryLocation = Path.Combine(webroot,pathToUplaod);
if(!Directory.Exists(DesiredDirectoryLocation))
{
Directory.CreateDirectory(DesiredDirectoryLocation);
}
string imageUrl = string.Empty;
var filename = Path.GetRandomFileName();
var newfilename = CreateUniqueFileName(file);
string pathwithfileName = DesiredDirectoryLocation + "/" + newfilename;
using (var fileStream = new FileStream(pathwithfileName, FileMode.Create))
{
await file.CopyToAsync(fileStream);
}
imageUrl = newfilename;
return imageUrl;
}
我尝试了两种不同的方法来创建缩略图,但其中任何一种都会出现上述错误
这是两种方法。
第一个是这样的:
public string CreateThumbImage(IFormFile uploadedFile, string desiredThumbPath,string desiredThumbFilename, int desiredThumbWidth, int desiredThumbHeight)
{
try
{
Stream filestream = uploadedFile.OpenReadStream();
Image thumbnailStream = Image.FromStream(filestream);
Image thumbnailImage = thumbnailStream.GetThumbnailImage(desiredThumbWidth, desiredThumbHeight, () => false, IntPtr.Zero);
string webroot = host.WebRootPath;
string DesiredDirectoryLocation = Path.Combine(webroot, desiredThumbPath);
if (!Directory.Exists(DesiredDirectoryLocation))
{
Directory.CreateDirectory(DesiredDirectoryLocation);
}
string thumbFullPathName = desiredThumbPath + "/" + desiredThumbFilename;
thumbnailImage.Save(thumbFullPathName);
return thumbFullPathName;
}
catch
{
throw;
}
}
第二个是这样的:
public void ResizeImage(IFormFile uploadedFile, string desiredThumbPath, int desiredWidth=0, int desiredHeight=0)
{
if (uploadedFile.Length > 0)
{
using (var stream = uploadedFile.OpenReadStream())
{
var uploadedImage = System.Drawing.Image.FromStream(stream);
//decide how to scale dimensions
if (desiredHeight == 0 && desiredWidth > 0)
{
var img = ImageResize.ScaleByWidth(uploadedImage, desiredWidth); // returns System.Drawing.Image file
img.SaveAs(desiredThumbPath);
}
else if(desiredWidth == 0 && desiredHeight > 0)
{
var img = ImageResize.ScaleByHeight(uploadedImage, desiredHeight); // returns System.Drawing.Image file
img.SaveAs(desiredThumbPath);
}
else
{
var img = ImageResize.Scale(uploadedImage, desiredWidth,desiredHeight); // returns System.Drawing.Image file
img.SaveAs(desiredThumbPath);
}
}
}
return;
}
这就是我调用方法的地方:
[HttpPost]
[ValidateAntiForgeryToken]
public async Task<ActionResult> Register(RegisterViewModel model)
{
FileUploadHelper uploadHelper = new FileUploadHelper(_host);
if (EmailValidation.EmailExists(model.EmailAddress,_context))
{
ModelState.AddModelError("EmailAddress", "This email address is already registered with us.");
}
if (model.Photo != null)
{
string[] extensions = new string[] { ".jpeg",".jpg", ".gif", ".png" };
///Validate the type of the image file being uploaded
ResponseMsg fileTypeValidated = uploadHelper.ValidateFileExtension(model.Photo, extensions);
if (!fileTypeValidated.ResponseStatus)
{
ModelState.AddModelError("Photo", fileTypeValidated.ResponseDescription);
}
///Validate the size of the image file being uploaded
ResponseMsg fileSizeValidated = uploadHelper.ValidateFilesize(model.Photo, 1);
if (!fileSizeValidated.ResponseStatus)
{
ModelState.AddModelError("Photo", fileSizeValidated.ResponseDescription);
}
}
if (ModelState.IsValid)
{
try
{
Instructor instructor = new Instructor
{
Surname = model.Surname,
OtherNames = model.Othernames,
Email = model.EmailAddress,
UserName = model.EmailAddress,
PhoneNumber = model.PhoneNumber,
Gender = model.Gender,
StateId = model.ResidenceState,
LgaId = model.ResidenceLga,
DateOfBirth = model.DateOfBirth,
TimeRegistered = DateTime.Now
};
var photo = await uploadHelper.SaveFileAsync(model.Photo,"images/instructors");
//Create image thumbnail for the instructor photo
var photo_thumbnail = "images/instructors/thumbs/" + photo;
uploadHelper.CreateThumbImage(model.Photo, "images/instructors/thumbs/", photo, 100, 100);...
如果您能指出我在哪里缺少正确的路径或在 ASP.NET-Core 2.* 中处理图像缩略图创建的更好方法以修复错误,请帮助我。
问候
解决方案
错误来自缩略图的路径。ResizeImage 方法中给出的路径并不表示缩略图的文件名。这就是通用 GDI+ 错误的来源。
因此,当调整大小的图像的路径(包括图像文件名)正确传递给SaveAs方法时,使用 ResizeImage 方法有效。这是工作方法:
public void ResizeImage(IFormFile uploadedFile, string desiredThumbPath, int desiredWidth=0, int desiredHeight=0)
{
string webroot = host.WebRootPath;
if (uploadedFile.Length > 0)
{
using (var stream = uploadedFile.OpenReadStream())
{
var uploadedImage = System.Drawing.Image.FromStream(stream);
//decide how to scale dimensions
if (desiredHeight == 0 && desiredWidth > 0)
{
var img = ImageResize.ScaleByWidth(uploadedImage, desiredWidth); // returns System.Drawing.Image file
img.SaveAs(Path.Combine(webroot,desiredThumbPath));
}
else if(desiredWidth == 0 && desiredHeight > 0)
{
var img = ImageResize.ScaleByHeight(uploadedImage, desiredHeight); // returns System.Drawing.Image file
img.SaveAs(Path.Combine(webroot,desiredThumbPath));
}
else
{
var img = ImageResize.Scale(uploadedImage, desiredWidth,desiredHeight); // returns System.Drawing.Image file
img.SaveAs(Path.Combine(webroot,desiredThumbPath));
}
}
}
return;
}
实现如下:
//Create image thumbnail for the instructor photo
var photo_thumbnail = "images/instructors/thumbs/" + photo;
uploadHelper.ResizeImage(model.Photo, photo_thumbnail, 100);
请记住在包含 ResizeImage 方法的 uploadHelper 的父类中包含以下 using 语句,如下所示:
using LazZiya.ImageResize;
同时,LazZiya.ImageResize 是用于在 asp.net-core 2.1 中管理图像大小调整的 nugget 包,请参阅 github 链接LazZiya 图像块的 Github 链接
因此,这解决了您在 asp.net-core 中的图像大小调整问题
问候
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