I have an ASP.NET MVC application where I am displaying images.
These images could be located on the file system or inside a database. This is fine as I can use Url.Action in my image, call the action on my controller and return the image from the relevant location.
However, I want to be able to support images stored in Amazon S3. In this case, I don't want my controller action to return the image, it should instead generate an image URL for Amazon S3.
Although I could just perform this logic inside my view e.g.
<%if (Model.Images[0].ImageLocation == ImageLocation.AmazonS3) {%>
// render amazon image
I need to ensure that the image exists first.
Essentially I need to pass a size value to my controller so that I can check that the image exists in that size (whether it be in the database, file system or amazon s3). Once I am sure that the image exists, then I return the URL to it.
Hope that makes sense,
Ben
Try the following approach.
A model class for an image tag.
public class ImageModel
{
public String Source { get; set; }
public String Title { get; set; }
}
Helper
public static String Image(this HtmlHelper helper, String source, String title)
{
var builder = new TagBuilder("img");
builder.MergeAttribute("src", source);
builder.MergeAttribute("title", title);
return builder.ToString();
}
View with Model.Images of type IEnumerable<ImageModel>
...
<%= Html.Image(Model.Images[0].Source, Model.Images[0].Title) %>
Action
public ActionResult ActionName(/*whatever*/)
{
// ...
var model = ...;
//...
var model0 = ImageModel();
if (Image0.ImageLocation == ImageLocation.AmazonS3)
model0.Source = "an amazon url";
else
model0.Source = Url.Action("GetImageFromDatabaseOrFileSystem", "MyController", new { Id = Image0.Id });
model0.Title = "some title";
model.Images.Add(model0);
// ...
return View(model);
}
An action is a kind of a pseudo code, however the idea should be clear.
After several iterations I have come up with a workable solution, although I'm still not convinced its the best solution.
Originally I followed Anton's suggestion and just set the image url accordingly within my controller action. This was simple enough with the following code:
products.ForEach(p =>
{
p.Images[0].Url = _mediaService.GetImageUrl(p.Images[0], 200);
});
However, I soon found that this approach did not give me the flexibility I needed. Often I will need to display images of different sizes and I don't want to use properties of my model for this such as Product.FullSizeImageUrl, Product.ThumbnailImageUrl.
As far as "Product" is concerned it only knows about the images that were originally uploaded. It doesn't need to know about how we manipulate and display them, or whether we are caching them in Amazon S3.
In web forms I might use a user control to display product details and then use a repeater control to display images, setting the image urls programatically in code behind.
I found that the use of RenderAction in ASP.NET MVC gave me similar flexibility:
Controller Action:
[ChildActionOnly]
public ActionResult CatalogImage(CatalogImage image, int targetSize)
{
image.Url = _mediaService.GetImageUrl(image, targetSize);
return PartialView(image);
}
Media Service:
public MediaCacheLocation CacheLocation { get; set; }
public string GetImageUrl(CatalogImage image, int targetSize)
{
string imageUrl;
// check image exists
// if not exist, load original image from store (fs or db)
// resize and cache to relevant cache location
switch (this.CacheLocation) {
case MediaCacheLocation.FileSystem:
imageUrl = GetFileSystemImageUrl(image, targetSize);
break;
case MediaCacheLocation.AmazonS3:
imageUrl = GetAmazonS3ImageUrl(image, targetSize);
break;
default:
imageUrl = GetDefaultImageUrl();
break;
}
return imageUrl;
}
Html helper:
public static void RenderCatalogImage(this HtmlHelper helper, CatalogImage src, int size) {
helper.RenderAction("CatalogImage", "Catalog", new { image = src, targetSize = size });
}
Usage:
<%Html.RenderCatalogImage(Model.Images[0], 200); %>
This now gives me the flexibility I require and will support both caching the resized images to disk or saving to Amazon S3.
Could do with some url utility methods to ensure that the generated image URL supports SSL / virtual folders - I am currently using VirtualPathUtility.
Thanks
Ben
You can create a HttpWebRequest to load the image. Check the header in the response, if it's 200 that means it was successful, otherwise something went wrong.
Related
I want to access and return a resource image from a DLL /connected project.
(Its a file, with build action of Resource). It is not listed in properties/resource as there are hundreds of them in the folder.
The idea is that I can call an image controller.
public ImageResult Display(string resourcePath){
Uri uri = new Uri("pack://application:,,,/ProjectName;component/Images/Vectors/" + resourcePath, UriKind.Absolute);
// What goes here??
}
The problem is i dont know how to turn the URI into an image, in MVC5.
I want to be able to call it from the view. using the url property of the <img> tag
I think you could try WebClient.DownloadData() method to download the image as byte array from specified URI, then convert it to Base64 format with Convert.ToBase64String() and display it on <img> tag using a string property in the viewmodel as src attribute value, below is an example to display the image:
Viewmodel Example
public class ViewModel
{
// other properties
// used to pass image into src attribute of img tag
public string ImageData { get; set; }
}
Controller Action
public ActionResult Display(string resourcePath)
{
Uri uri = new Uri("pack://application:,,,/ProjectName;component/Images/Vectors/" + resourcePath, UriKind.Absolute);
using (var wc = new System.Net.WebClient())
{
// download URI resource as byte array
byte[] image = wc.DownloadData(uri);
// get image extension
string path = string.Format("{0}{1}{2}{3}", uri.Scheme, Uri.SchemeDelimiter, uri.Authority, uri.AbsolutePath);
string extension = System.IO.Path.GetExtension(path).Replace(".", "");
// assign image to viewmodel property as Base64 string format
var model = new ViewModel();
model.ImageData = string.Format("data:image/{0};base64,{1}", extension, Convert.ToBase64String(image));
return View(model);
}
}
View
#model ViewModel
<img src="#Model.ImageData" ... />
Additional note:
If you already know the extension from the resource URI, you could use it directly instead of using Path.GetExtension, here is an example for JPG format:
model.ImageData = string.Format("data:image/jpg;base64,{0}", Convert.ToBase64String(image));
Related issues:
Image to byte array from a url
MVC How to display a byte array image from model
Be sure to register the pack:// scheme as this won't automatically be registered in an MVC app as it is in a WPF app.
In this example code, Blarn0 is a public property in my model class to ensure that the access to the PackUriHelper.UriSchemePack property isn't optimized away when the code is published in Release configuration. I'm sure one can use discards for this very purpose in later versions of C#.
const string scheme = "pack";
if (!UriParser.IsKnownScheme(scheme))
Blarn0 = PackUriHelper.UriSchemePack;
I have here an image rendering method on my api that is being access via url by users in order to display images as source. I don't have a problem when testing locally since I'm only making single user requests. But by the time I deployed it, staging/production testers comes in. The image being rendered is broken because of an internal server error, I'm guessing it is because of the multiple request.
Here's how I do it:
[Route("userprofileimage")]
public class UserProfileImageController : Controller
{
[Route("render")]
public FileResult Render(string di, string tk, string fi)
{
if (!string.IsNullOrEmpty(di) && !string.IsNullOrEmpty(tk) && !string.IsNullOrEmpty(fi))
{
var filePath = Path.Combine(Path.Combine(Server.MapPath("~/App_Data/UserProfileImages"), fi));
var isValid = new UserTokenService().ValidateUserToken(Guid.Parse(di), tk);
if(isValid)
{
if (ImageFileNotAvailable(filePath))
return new FileStreamResult(new FileStream(Path.Combine(Server.MapPath("~/App_Data/UserProfileImages"), "default.png"), FileMode.Open), "image/png");
else
return new FileStreamResult(new FileStream(filePath, FileMode.Open), "image/png");
}
}
return new FileStreamResult(new FileStream(Path.Combine(Server.MapPath("~/App_Data/UserProfileImages"), "default.png"), FileMode.Open), "image/png");
}
private bool ImageFileNotAvailable(string fullFilePath)
{
return !System.IO.File.Exists(fullFilePath);
}
}
As you can see there are token and id checks before the actual rendering of the image.
I have no specific reason on my approach on this one. I just find it convenient to have links as image sources.
I was expecting that the requests from multiple users will wait until a previous execution is done before going in but I guess they go in simultaneously. So at some point the file is currently open or being manipulated and another request comes in. Hence the error.
Any ideas on how can I improve this?
In my MVC 5 app I need to be able to dynamically construct a list of fully qualified external URL hyperlinks, alone with some additional data, which will come from the Model passed in. I figure - I will need to construct my anchor tags something like this:
{{linkDisplayName}}
with AngularJS this would be natural, but, I have no idea how this is done in MVC.
Is there a templating library that can be used for this?
1) Create a model to Hold the Links
public class LinkObject
{
public string Link { get; set; }
public string Description { get; set; }
}
2) In your Action you can use ViewBag, ViewData or even pass the list inside you Model. I will show you how to do using ViewBag
public ActionResult MyDynamicView()
{
//Other stuff and code here
ViewBag.LinkList = new List<LinkObject>()
{
new LinkObject{ Link ="http://mylink1.com", Description = "Link 1"},
new LinkObject{ Link ="http://mylink2.com", Description = "Link 2"},
new LinkObject{ Link ="http://mylink3.com", Description = "Link 3"}
};
return View(/*pass the model if you have one*/);
}
3) In the View, just use a loop:
#foreach (var item in (List<LinkObject>)ViewBag.LinkList)
{
#item.Description
}
Just create a manual one for that, no need to do it from a template. For example, in javascript
function groupAnchor(url,display){
var a = document.createElement("a");
a.href = url;
a.className = "list-group-item";
a.target = "_blank";
a.innerHTML = display;
return a;
}
And then use that function to modify your html structure
<div id="anchors"></div>
<script>
document.getElementById("anchors").appendChild(groupAnchor("http://google.com","Google"));
</script>
Your approach to modification will more than likely be more advanced than this, but it demonstrates the concept. If you need these values to come from server side then you could always iterate over a set using #foreach() and issue either the whole html or script calls there -- or, pass the set from the server in as json and then use that in a function which is set up to manage a list of anchors.
To expand on this, it is important to avoid sending html to the view from a razor iteration. The reason being that html constructed by razor will increase the size of the page load, and if this is done in a list it can be a significant increase.
In your action, construct the list of links and then serialize them so they can be passed to the view
public ActionResult ViewWithLinks()
{
var vm = new ViewModel();
vm.Links = Json(LinkSource.ToList()).Data;
//or for a very simple test for proof of concept
var Numbers = Json(Enumerable.Range(0,100).ToList()).Data;
ViewData["numbers"] = Numbers ;
return View(vm);
}
where all you need is an object to hold the links in your view model
public class ViewModel
{
public ICollection<Link> Links { get; set; }
}
public class Link
{
public string text { get; set; }
public string href { get; set; }
}
and then in your view you can consume this json object
var allLinks = #Html.Raw(Json.Encode(Model.Links));
var numbersList = #Html.Raw(Json.Encode(ViewData["linkTest"]));//simple example
Now you can return to the above function in order to place it on the page by working with the array of link objects.
var $holder = $("<div>");
for(var i = 0; i < allLinks.length; i++){
$holder.append(groupAnchor(allLinks[i].href,allLinks[i].text));
}
$("#linkArea").append($holder);
The benefit is that all of this javascript can be cached for your page. It is loaded once and is capable of handling large amounts of links without having to worry about sending excessive html to the client.
I get a picture by uploading and I want to convert it to image file without save it.
how can I do it?
public HttpPostedFileBase BasicPicture { get; set; }
var fileName = Path.GetFileName(BasicPicture.FileName);
// store the file inside ~/App_Data/uploads folder
var path = Path.Combine(Server.MapPath("~/App_Data/uploads"), fileName);
BasicPicture.SaveAs(path);
By this code I can save the picture on the server but I want convert it to image
like
Image img=(Image) BasicPicture;
but it doesn't work.
You could use the FromStream method:
using (Image img = Image.FromStream(BasicPicture.InputStream))
{
... do something with the image here
}
You can also convert HttpPostedFileBase to WebImage (which gives you more API - like method Resize):
public ActionResult SaveUploadedImage(HttpPostedFileBase file)
{
if(file != null)
{
var image = new System.Web.Helpers.WebImage(file.InputStream);
var path = Path.Combine(Server.MapPath("~/App_Data/uploads"), file.FileName);
image.Save(path);
}
return View();
}
With out knowing exactly what you are doing and why i can give a full intelligent answer.
Personally i would use something like this to open an image. You have saved the image to your server, so instead of casting why not new up a new image? the end result is the same!
WebImage webImage = new WebImage(path);
I'm using MVC 3 and using the AjaxUpload plugin to upload an image using AJAX. I don't want to save the image in the file system, instead save it to the session object and then output the stream to populate an image control on the form? Would anyone know how to do this?
No idea why would ever want to do that (store the file in session) because if you have lots of users uploading their files at the same time, storing those files in the memory of your web server, especially if those files are big, won't make this server last very long. Storing the file on the filesystem is the recommended approach.
But anyway, here's how you could do it (assuming you didn't read or cared about my previous remark):
[HttpPost]
public ActionResult Upload(MyViewModel model)
{
if (!ModelState.IsValid)
{
return View(model);
}
var buffer = new byte[model.File.InputStream];
model.File.InputStream.Read(buffer, 0, buffer.Length);
Session["uploadedFile"] = buffer;
return View(model);
}
where the File property on the view models is a HttpPostedFileBase. Next you could have a controller action which will serve this file:
public ActionResult Image()
{
byte[] buffer = (byte[])Session["uploadedFile"];
return File(buffer, "image/png");
}
and in the view you will have an <img> tag pointing to this action:
<img src="#Url.Action("image")" alt="" />
Now of course the AjaxUpload plugin allows you to upload the file using AJAX, so you don't need to reload the entire page. So in this case your controller action could simply return a JSON object to indicate whether the upload process succeeded and then in the success callback set the src property of the <img> tag to the controller action that will serve the file.
SomeView.cshtml:
<img src="#Url.Action("/Image/Render")" />
ImageController.cs:
public ActionResult Render() {
return File((byte[])Session["Avatar"], "image/jpeg")
}
Some example code. Modify it to whatever you want to do. Not really a good idea to sling an image into a session if lots of users. Better to stick it into a db if short lived, or if long lived, a more permanent storage (filesystem maybe).
public ActionResult UploadImage()
{
foreach (string imageName in Request.Files)
{
HttpPostedFileBase file = Request.Files[imageName];
if (file.ContentLength > 0)
{
BinaryReader br = new BinaryReader(file.InputStream);
byte[] content = br.ReadBytes(file.ContentLength);
Session[imageName] = content; // better to store in a db here
}
}
return View();
}
// return the image (controller action) /mycontroller/ViewImage?imageName=whatever
public FileStreamResult ViewImage(string imageName)
{
byte[] content = (byte[])Session[imageName] ; // where ever your content is stored (ideally something other than session)
MemoryStream ms = new MemoryStream(content);
return new FileStreamResult(ms, "application/octet-stream"); // set content type based on input image, it might be png, jpg, gif etc.,
}
Hope this helps.