I have an incorrect way to make asp.net mvc serve a filestream. It looks like this:
public void SlideThumbnail(Guid id, int? width, int? height)
{
/*make the thumbnail code here*/
using (Bitmap thumbnail = imageThumb.Generate(path))
{
var msOutput = new MemoryStream();
thumbnail.Save(msOutput, ImageFormat.Png);
Response.ContentType = "image/png";
msOutput.WriteTo(Response.OutputStream);
}
}
This works super duper. I tried modifying the code to use base.File() instead. Like this:
public ActionResult SlideThumbnail(Guid id, int? width, int? height)
{
/*make the thumbnail code here*/
using (Bitmap thumbnail = imageThumb.Generate(path))
{
var msOutput = new MemoryStream();
thumbnail.Save(msOutput, ImageFormat.Png);
return base.File(msOutput, "image/png");
}
}
But all this doesn't seem to actually do anything. I don't get any errors, but I also don't get any image :-(
So how do i accomplish this the MVC way?
We figured it out. I just needed to add:
thumbnail.Save(msOutput, ImageFormat.Png);
msOutput.Seek(0, SeekOrigin.Begin); // <--- this line
return base.File(msOutput, "image/png");
and we're all good.
Related
I'm working on Xmarin Forms(PCL) project, I want to convert the StackLayout to Image / buffer and send it to printer for hard print.
Can anyone suggest how to do it in (Xamarin.Android & Xamarin.iOS).
You can't. Xamarin does not have that kind of feature. You should write a Renderer for your UIComponent.
Fortunately there is an Objective-C iOS implementation, and an Android one as well. You can inspire from them.
Taken from this link, which I have personally used, quite a while back though, the following code will take a screenshot of the entire page.
I ended up modifying the code to only take a screenshot of a specific view on the page and also changed a few other things but this example is what I based it off of, so let me know if you would rather see that code and/or if something below is not working for you.
First you create an interface in your Forms project, IScreenshotManager.cs for example:
public interface IScreenshotManager {
Task<byte[]> CaptureAsync();
}
Now we need to implement our interface in Android, ScreenshotManager.cs for example:
public class ScreenshotManager : IScreenshotManager {
public static Activity Activity { get; set; }
public async System.Threading.Tasks.Task<byte[]> CaptureAsync() {
if(Activity == null) {
throw new Exception("You have to set ScreenshotManager.Activity in your Android project");
}
var view = Activity.Window.DecorView;
view.DrawingCacheEnabled = true;
Bitmap bitmap = view.GetDrawingCache(true);
byte[] bitmapData;
using (var stream = new MemoryStream()) {
bitmap.Compress(Bitmap.CompressFormat.Png, 0, stream);
bitmapData = stream.ToArray();
}
return bitmapData;
}
}
Then set ScreenshotManager.Activity in MainActivity:
public class MainActivity : Xamarin.Forms.Platform.Android.FormsApplicationActivity {
protected override async void OnCreate(Android.OS.Bundle bundle) {
...
ScreenshotManager.Activity = this; //There are better ways to do this but this is what the example from the link suggests
...
}
}
Finally we implement this on iOS, ScreenshotManager.cs:
public class ScreenshotManager : IScreenshotManager {
public async System.Threading.Tasks.Task<byte[]> CaptureAsync() {
var view = UIApplication.SharedApplication.KeyWindow.RootViewController.View;
UIGraphics.BeginImageContext(view.Frame.Size);
view.DrawViewHierarchy(view.Frame, true);
var image = UIGraphics.GetImageFromCurrentImageContext();
UIGraphics.EndImageContext();
using(var imageData = image.AsPNG()) {
var bytes = new byte[imageData.Length];
System.Runtime.InteropServices.Marshal.Copy(imageData.Bytes, bytes, 0, Convert.ToInt32(imageData.Length));
return bytes;
}
}
}
i have a view where i put the id of the event then i can download all the images for that event.....
here's my code
[HttpPost]
public ActionResult Index(FormCollection All)
{
try
{
var context = new MyEntities();
var Im = (from p in context.Event_Photos
where p.Event_Id == 1332
select p.Event_Photo);
Response.Clear();
var downloadFileName = string.Format("YourDownload-{0}.zip", DateTime.Now.ToString("yyyy-MM-dd-HH_mm_ss"));
Response.ContentType = "application/zip";
Response.AddHeader("content-disposition", "filename=" + downloadFileName);
using (ZipFile zipFile = new ZipFile())
{
zipFile.AddDirectoryByName("Files");
foreach (var userPicture in Im)
{
zipFile.AddFile(Server.MapPath(#"\") + userPicture.Remove(0, 1), "Files");
}
zipFile.Save(Response.OutputStream);
//Response.Close();
}
return View();
}
catch (Exception ex)
{
return View();
}
}
The problem is that each time i get html page to download so instead of downloading "Album.zip" i get "Album.html" any ideas???
In MVC, rather than returning a view, if you want to return a file, you can return this as an ActionResult by doing:
return File(zipFile.GetBytes(), "application/zip", downloadFileName);
// OR
return File(zipFile.GetStream(), "application/zip", downloadFileName);
Don't mess about with manually writing to the output stream if you're using MVC.
I'm not sure if you can get the bytes or the stream from the ZipFile class though. Alternatively, you might want it to write it's output to a MemoryStream and then return that:
var cd = new System.Net.Mime.ContentDisposition {
FileName = downloadFileName,
Inline = false,
};
Response.AppendHeader("Content-Disposition", cd.ToString());
var memStream = new MemoryStream();
zipFile.Save(memStream);
memStream.Position = 0; // Else it will try to read starting at the end
return File(memStream, "application/zip");
And by using this, you can remove all lines in which you are doing anything with the Response. No need to Clear or AddHeader.
I have my controller
[HttpPost]
public ActionResult ChangeAvatar(HttpPostedFileBase file)
{
AvatarHelper.AvatarUpdate(file, User.Identity.Name);
return RedirectToAction("Index", "Profile");
}
And I already check if file is in jpeg/png format:
private static bool IsImage(string contentType)
{
return AllowedFormats.Any(format => contentType.EndsWith(format,
StringComparison.OrdinalIgnoreCase));
}
public static List<string> AllowedFormats
{
get { return new List<string>() {".jpg", ".png", ".jpeg"}; }
}
What I need - it ensure that uploaded file is real image file and not txt file with image extension.
I convert my uploaded file like this:
using (var image = System.Drawing.Image.FromStream(postedFile.InputStream))
{
///image stuff
}
I am thinking about try/catch block on creating image from input stream but I wonder if there is good way to do it?
Thanks)
P.S.
I wonder if there is another (more efficient way that try/catch block) way to check whether file is real image?
You could use the RawFormat property:
private static ImageFormat[] ValidFormats = new[] { ImageFormat.Jpeg, ImageFormat.Png };
public bool IsValid(Stream image)
{
try
{
using (var img = Image.FromStream(file.InputStream))
{
return ValidFormats.Contains(img.RawFormat);
}
}
catch
{
return false;
}
}
Also you could put this validation logic into a reusable validation attribute as I have shown in this post.
My solution as an extension, actually checking if a base64 string is an image or not:
public static bool IsImage(this string base64String)
{
byte[] imageBytes = Convert.FromBase64String(base64String);
var stream = new MemoryStream(imageBytes, 0, imageBytes.Length);
try
{
stream.Write(imageBytes, 0, imageBytes.Length);
System.Drawing.Image image = System.Drawing.Image.FromStream(stream, true);
return true;
}
catch (Exception)
{
return false;
}
}
Usage:
if(!"base64string".IsImage())
throw new Exception("Not an image");
I have a MVC application, which creates a Chart in the business logic like this:
StatisticsModel.Chart.Width = 150
StatisticsModel.Chart.Height = 300
StatisticsModel.Chart.Attributes.Add("align", "left")
StatisticsModel.Chart.Titles.Add("Statistics for: " + StatisticsModel.ProductNumbers)
StatisticsModel.Chart.ChartAreas.Add(New ChartArea)
StatisticsModel.Chart.Series.Add(New Series)
StatisticsModel.Chart.Series(0).ChartType = SeriesChartType.Column
StatisticsModel.Chart.Series(0).Points.DataBindXY(StatisticsModel.FailedTPDescriptionList, "key", StatisticsModel.FailedTPDescriptionList, "value")
Now, I am trying to implement it in the View, but I have read many articles, and they suggest me to put the chart in a different controller. But that would mean I have to send the Chart object there, as I have many functions, that require a chart, and I thought the easiest way is to implement it in the Model, and then rendering it from there.
I tried using: http://code-inside.de/blog-in/2008/11/27/howto-use-the-new-aspnet-chart-controls-with-aspnet-mvc/
But the:
#Code
Dim writer As New HtmlTextWriter(Page.Response.Output)
End Code
Didn't work for me. I am using VB.NET
Can anyone help me? Suggestions are very welcome.
There are many, many ways of creating and showing charts in MVC, and the link you referred to is pretty good IMHO. I'm using c#, but the way I'm doing it is to use an img-tag in the view and point the src-attribute to a Controller action:
<img id="diagram" src="<%=Url.Action("DrawChartImage", "Home") %>" alt="Chart Diagram" />
The controller action returns a FileContentResult:
public ActionResult DrawChartImage()
{
using (var chartHelper = new ChartHelper())
{
//get data
var data = GetSomeDataForTheChart();
//draw chart
chartHelper.Draw(data);
//return chart as png image
return File(chartHelper.Image, "image/png");
}
}
The ChartHelper class implements IDisposable and has a helper property (Image) which returns the chart as a file, NOTE this is just sample/snippet code to show what I mean:
public class ChartHelper : IDisposable
{
private readonly Chart _chart;
public Chart Chart
{
get
{
return _chart;
}
}
public byte[] Image
{
get
{
using (var ms = new MemoryStream())
{
_chart.SaveImage(ms);
return ms.GetBuffer();
}
}
}
public ChartHelper()
{
_chart = new Chart();
_chart.Height = 300;
_chart.Width = 800;
_chart.ImageType = ChartImageType.Png;
_chart.Titles.Add("some title");
_chart.Legends.Add("some legend");
_chart.ChartAreas.Add("some chart area");
}
public void Draw(List<Data> data)
{
var dataArrays = GetDataArrays(data); //another helper method...
var series = new Series(tag);
series.Name = tag;
series.Legend = "tags";
series.ChartType = SeriesChartType.Spline;
series.BorderWidth = 4;
//sample way to add data below...
series.Points.DataBindXY(dataArrays.Item1, dataArrays.Item2);
_chart.Series.Add(series);
}
public void Dispose()
{
_chart.Dispose();
}
}
Works pretty well for me, hope it helps even if it's in C#.
EDIT If you want to create the image/chart in business logic called from your "main" Controller action, maybe you can do something like this where you generate the image/chart and then save it to disk, cache or database and pick it up from the image rendering controller action:
public ActionResult Index()
{
//this is call to your business logic or similar which generates the chart
byte[] image = GenerateImage();
//save image to cache, disk or from database
HttpContext.Cache["image"] = image;
return View();
}
public ActionResult Image()
{
//get image from cache, disk or from database
var image = HttpContext.Cache["image"] as byte[];
return File(image, "image/png");
}
//some sample/dummy code to generate image from a template
private byte[] GenerateImage()
{
using (var ms = new MemoryStream())
{
using (var image = System.Drawing.Image.FromFile(#"c:/temp/template.png"))
using (var brush = new SolidBrush(System.Drawing.Color.Black))
using (var bmp = new System.Drawing.Bitmap(image, image.Width, image.Height))
using (var g = System.Drawing.Graphics.FromImage(bmp))
{
g.DrawString(DateTime.Now.ToLongTimeString(), new Font("Consolas", 10), brush, 10, 10);
bmp.Save(ms, ImageFormat.Png);
}
return ms.ToArray();
}
}
And the view would be:
<img src="#Url.Action("Image")"/>
I'm trying to serve a txt file made from the database using an action. The action is the following:
public ActionResult ATxt()
{
var articulos = _articulosService.ObteTotsArticles();
return File(CatalegATxt.ATxt(articulos), "text/plain");
}
and the CatalegATxt class is:
using System;
using System.Collections.Generic;
using System.IO;
using System.Text;
using WebDibaelsaMVC.DTOs.Busqueda;
namespace WebDibaelsaMVC.TxtLib
{
public static class CatalegATxt
{
public static Stream ATxt(IEnumerable<ArticuloBusquedaDTO> articles)
{
var stream = new MemoryStream();
var streamWriter = new StreamWriter(stream, Encoding.UTF8);
foreach (ArticuloBusquedaDTO article in articles)
{
streamWriter.WriteLine(article.ToStringFix());
}
stream.Seek(0, SeekOrigin.Begin);
return stream;
}
public static string ToStringFix(this ArticuloBusquedaDTO article)
{
string result = "";
result += article.CodigoArticulo.PadRight(10, ' ').Substring(0, 10);
result += article.EAN.Trim().PadLeft(13, '0').Substring(0, 13);
result += article.NombreArticulo.PadRight(100, ' ').Substring(0, 100);
result += article.Marca.PadRight(100, ' ').Substring(0, 100);
result += article.Familia.PadRight(50, ' ').Substring(0, 50);
result += article.PrecioCesion.ToStringFix();
result += article.PVP.ToStringFix();
return result;
}
private static string ToStringFix(this double numero)
{
var num = (int)Math.Round(numero * 100, 0);
string result = num.ToString().PadLeft(10, '0');
return result;
}
}
}
it just writes the file lines based on the stuff I got from the database. But when I look at the file it looks truncated. The file is about 8Mb. I also tried converting to byte[] before returning from ATxt with the same result.
Any idea?
Thanks,
Carles
Update: I also tried to serve XML from the same content and it also gets truncated. It doesn't get truncated on the data (I thought it might have been an EOF character in it) but it truncates in the middle of a label...
I was having the exact same problem. The text file would always be returned as truncated.
It crossed my mind that it might be a "flushing" problem, and indeed it was. The writer's buffer hasn't been flushed at the end of the operation - since there's no using block, or the Close() call - which would flush automatically.
You need to call:
streamWriter.Flush();
before MVC takes over the stream.
Here's how your method should look like:
public static Stream ATxt(IEnumerable<ArticuloBusquedaDTO> articles)
{
var stream = new MemoryStream();
var streamWriter = new StreamWriter(stream, Encoding.UTF8);
foreach (ArticuloBusquedaDTO article in articles)
{
streamWriter.WriteLine(article.ToStringFix());
}
// Flush the stream writer buffer
streamWriter.Flush();
stream.Seek(0, SeekOrigin.Begin);
return stream;
}
Why are you using an ActionResult?
ASP.NET MVC 1 has a FileStreamResult for just what you are doing. It expects a Stream object, and returns it.
public FileStreamResult Test()
{
return new FileStreamResult(myMemoryStream, "text/plain");
}
Should work fine for what you want to do. No need to do any conversions.
In your case, just change your method to this:
public FileStreamResult ATxt()
{
var articulos = _articulosService.ObteTotsArticles();
return new FileStreamResult(CatalegATxt.ATxt(articulos), "text/plain");
}
You probably want to close the MemoryStream. It could be getting truncated because it expects more data still. Or to make things even simpler, try something like this:
public static byte[] ATxt(IEnumerable<ArticuloBusquedaDTO> articles)
{
using(var stream = new MemoryStream())
{
var streamWriter = new StreamWriter(stream, Encoding.UTF8);
foreach (ArticuloBusquedaDTO article in articles)
{
streamWriter.WriteLine(article.ToStringFix());
}
return stream.ToArray();
}
}