I am trying download an image from a website and put it in a picturebox.
// response contains HttpWebResponse of the page where the image is
using (Stream inputStream = response.GetResponseStream()) {
using (Stream outputStream = File.Open(fileName, FileMode.Create)) {
byte[] buffer = new byte[4096];
int bytesRead;
do {
bytesRead = inputStream.Read(buffer, 0, buffer.Length);
outputStream.Write(buffer, 0, bytesRead);
} while (bytesRead != 0);
}
}
response.Close();
After that, the downloaded image is assigned to a PictureBox like such:
if (imageDownloaded) {
pictureBox1.Image = Image.FromFile(filePath);
}
This all works like a charm first time, but the second time I run the code I get System.IO.IOException: "Additional information: The process cannot access the file ...(file path) ... because it is being used by another process.". I have no idea why...
I looked at 4 other threads such as this one, but they were basically stressing out the need to close streams, which I do, so none of them helped me.
Before you recommend to use pictureBox1.Load() I can't because I need the image downloaded for further development.
EDIT 1: I have actually tried to dispose the image by putting pictureBox1.Image = null before the code above is executed. It is still giving me an exception.
The Image.FromFile docs state:
The file remains locked until the Image is disposed.
So you need to dispose your Image too to be able to overwrite the file.
Try using the Clone method on your image and dispose the original Image.
The thing is related to the Image.FromFile. If we read a documentation, there is a note:
The file remains locked until the Image is disposed.
This pretty much explains the behavior you get.
To resolve this, you might need to create a copy of the image and assign it to a PictureBox .
From MSDN:
The file remains locked until the Image is disposed.
This means its the PictureBox that is holding the file open.
You have two options:
Dispose of the PictureBox image before writing the new file.
Download the file, make a copy of it and load the copy into the PictureBox - this allows you to write over the downloaded file freely.
I'll be the contrarian here. :)
While cloning/copying the image will resolve the exception, it raises a different question: why are you overwriting to the same file for a new image?
It seems to me that a better approach would be to download subsequent files to different file names (if they are really different files), or to simply reuse the file already downloaded instead of hitting the network again (if it's just a new request for the same file).
Even if you want to repeatedly download the same file (perhaps you expect the actual file contents to change), you can still download to a new name (e.g. append a number to the file name, use a GUID for the local file name, etc.)
Related
I have build a program which allows me to insert comment and the title of an Image through System.Image.Drawing so right now, I have trouble trying to overwrite the existing Jpeg file with the one that has comment and title added into it, but I am encountering error while deleting the file, so I'm not sure what to do as I have tried disposing the file but I cant saved it in that case, due to the fact that I disposed it too early, but I cant saved it because the existing file name is not deleted so I'm kinda stuck in the middle right now.
Here are my codes for it:
public string EditComment(string OriginalFilepath, string newFilename)
{
image = System.Drawing.Image.FromFile(OriginalFilepath);
PropertyItem propItem = image.PropertyItems[0];
using (var file = System.Drawing.Image.FromFile(OriginalFilepath))
{
propItem.Id = 0x9286; // this is the id for 'UserComment'
propItem.Type = 2;
propItem.Value = System.Text.Encoding.UTF8.GetBytes("HelloWorld\0");
propItem.Len = propItem.Value.Length;
file.SetPropertyItem(propItem);
PropertyItem propItem1 = file.PropertyItems[file.PropertyItems.Count() - 1];
file.Dispose();
image.Dispose();
string filepath = Filepath;
if (File.Exists(#"C:\Desktop\Metadata"))
{
System.IO.File.Delete(#"C:\Desktop\Metadata");
}
string newFilepath = filepath + newFilename;
file.Save(newFilepath, ImageFormat.Jpeg);//error appears here
return filepath;
}
}
The Error shown are:
An exception of type 'System.ArgumentException' occurred in System.Drawing.dll but was not handled in user code
Additional information: Parameter is not valid.
The problem is that opening an image from file locks the file. You can get around that by reading the file into a byte array, creating a memory stream from that, and then opening the image from that stream:
public string EditComment(string originalFilepath, string newFilename)
{
Byte[] bytes = File.ReadAllBytes(originalFilepath);
using (MemoryStream stream = new MemoryStream(bytes))
using (Bitmap image = new Bitmap(stream))
{
PropertyItem propItem = image.PropertyItems[0];
// Processing code
propItem.Id = 0x9286; // this is the id for 'UserComment'
propItem.Type = 2;
propItem.Value = System.Text.Encoding.UTF8.GetBytes("HelloWorld\0");
propItem.Len = propItem.Value.Length;
image.SetPropertyItem(propItem);
// Not sure where your FilePath comes from but I'm just
// putting it in the same folder with the new name.
String newFilepath;
if (newFilename == null)
newFilepath = originalFilePath;
else
newFilepath = Path.Combine(Path.GetDirectory(originalFilepath), newFilename);
image.Save(newFilepath, ImageFormat.Jpeg);
return newFilepath;
}
}
Make sure you do not dispose your image object inside the using block as you did in your test code. Not only does the using block exist exactly so you don't have to dispose manually, but it's also rather hard to save an image to disk that no longer exists in memory. Similarly, you seem to open the image from file twice. I'm just going to assume all of those were experiments to try to get around the problem, but do make sure to clean those up.
The basic rules to remember when opening images are these:
An Image object created from a file will lock the file during the life cycle of the image object, preventing the file from being overwritten or deleted until the image is disposed.
An Image object created from a stream will need the stream to remain open for the entire life cycle of the image object. Unlike with files, there is nothing actively enforcing this, but after the stream is closed, the image will give errors when saved, cloned or otherwise manipulated.
Contrary to what some people believe, a basic .Clone() call on the image object will not change this behaviour. The cloned object will still keep the reference to the original source.
Note, if you actually want a usable image object that is not contained in a using block, you can use LockBits and Marshal.Copy to copy the byte data of the image object into a new image with the same dimensions and the same PixelFormat, effectively making a full data clone of the original image. (Note: I don't think this works on animated GIF files) After doing that, you can safely dispose the original and just use the new cleanly-cloned version.
There are some other workarounds for actually getting the image out, but most of them I've seen aren't optimal. These are the two most common other valid workarounds for the locking problem:
Create a new Bitmap from an image loaded from file using the Bitmap(Image image) constructor. This new object will not have the link to that file, leaving you free to dispose the one that's locking the file. This works perfectly, but it changes the image's colour depth to 32-bit ARGB, which might not be desired. If you just need to show an image on the UI, this is an excellent solution, though.
Create a MemoryStream as shown in my code, but not in a using block, leaving the stream open as required. Leaving streams open doesn't really seem like a good idea to me. Though some people have said that, since a MemoryStream is just backed by a simple array, and not some external resource, the garbage collector apparently handles this case fine...
I've also seen some people use System.Drawing.ImageConverter to convert from bytes, but I looked into the internals of that process, and what it does is actually identical to the last method here, which leaves a memory stream open.
I'm having some really weird problems trying to load a file pragmatically into my project to save to a local folder.
I can load the file fine in my .xaml code, as so:
<BitmapImage x:Key="Image" UriSource ="/Assets/Submandibular_oedema.jpg" />
And I can display that image on my page. However, when I try to load the image and use it in my xaml.cs code like this
uriMyFile = new Uri("/Assets/Submandibular_oedema.jpg", UriKind.RelativeOrAbsolute);
It cannot find the file and as a result, won't let me do anything with the URI.
For background, my aim is to get the image stream then save it to a local folder.
I know it'll be a stupid little problem, but I can't find any solutions to it.
Thanks!
Try full path (specify your project assembly)
uriMyFile = new Uri("/YourAssemblyName;component/Assets/Submandibular_oedema.jpg",UriKind.RelativeOrAbsolute);
Update after Starktastics comment:
I finally understood your problem: you need the Application.GetResourceStream method to retrieve a stream of your resource, read from that stream and write it to a file stream.
var streamResourceInfo = Application.GetResourceStream(uri);
var stream = streamResourceInfo.Stream;
var byteBuffer = new byte[stream.Length];
using (stream)
{
stream.Read(byteBuffer, 0, byteBuffer.Length);
}
using (var fileStream = new FileStream("photo.jpg", FileMode.Create))
{
fileStream.Write(byteBuffer, 0, byteBuffer.Length);
}
I've updated the solution that you can download here.
Original answer:
If you use a WPF application, make sure that the asset you added to your project is to Build Action 'Resource'. You can check that in the properties pane after you clicked the file.
In any case, your syntax for the URI is correct. I checked it in a small project myself and it works. You can download it here (DropBox link)
Feel free to leave a comment.
Try to use
uriMyFile=new Uri("ms-appx:///Assets/YourImage.png"));
This works for me while trying to show a diffrent map icon for each place.
I am having a really weird issue with my image saving method. First, here is the method:
public static void uploadImageToServer(string savePath, HttpPostedFile imageToUpload, bool overwrite)
{
byte[] myData = new Byte[imageToUpload.ContentLength];
imageToUpload.InputStream.Read(myData, 0, imageToUpload.ContentLength);
FileStream newFile = new FileStream(savePath, FileMode.Create);
newFile.Write(myData, 0, myData.Length);
newFile.Close();
}
As you can see from the input parameters this method works in conjuction with the FileUpload control. Now I am using this method from two pages which both have a FileUpload control. On one page the image uploads file, on the other page it results in a corrupted file.
I am really at a loss as to why the image is being corrupted. I am using the same image, the same method, and the same input control.
Is there any way I can debug this?
Gonna steal alexn's answer <_<
You are over-complicating it. Just use the built-in FileUpload::SaveAs(save_path) that is provided for you.
You can use the Server.MapPath() method to help you get a dynamic path to your root directory, go from there and append the file name to it.
Not sure why you are getting that error. My best guess is either your savePath is broken (or the filename/extension appended to it), or the bytes are not being read/written to perfectly.. Anyway, you should not get that error by using the method I described (considering you don't mess up the file extension :).
I want to delete a file on my computer but the app throws an exception that The directory is busy. My first thought is to implement a dispose method in my class which does a file delete.
Knows anybody how to do this?
It's actually a Picturebox which displays a image and if you click on a button beside the image you can remove it, thus deleting it. It's propably that which blocks my filepath.
picobx.Image = Image.FromFile(//path)
Is there any solution to this?
PS. I want to dispose the resource so that I can delete...
do like this:
File.Delete(// path )
The Image.FromFile method actually locks the file thats why you can't delete it. The best would be to read the image as a byte array using bytes = File.ReadBytes(filename), create a memorystream from the byte array, pass the memory stream to Image.FromStream to display the image and then delete it with the button click.
OK - I see what you are tring to do.
Image itself implements IDisposable. You don't need to implement IDisposable yourself, you just have to make sure you either call Dispose on your image, or use the "using" syntax.
The problem is that until the image - the returned reference from Image.FromFile(//path) - is disposed of, it still locks the underlying file so you will always get the exception "The process cannot access the file"
What you intend to do is the following, I suppose:
try {
File.Delete(yourFile);
}
catch (IOException ex) {
// Do something with the exception here, like showing the user that the file can't be deleted)
}
A file that i.e. is in use or in an directory with insufficient rights can't be deleted. So if you get an error, you should look why the file is in use / not accessible, whatever.
Based on your edit, I suggest to do the following:
Image myImage = Image.FromFile(//path);
picobx.Image = myImage;
//click button
picobx.Image = null;
myImage.Dispose();
File.Delete(//path);
As you have suggested you will need to dispose of the image before you can delete it something like this:
Image i = this.pictureBox1.Image;
this.pictureBox1.Image = null;
i.Dispose();
File.Delete(filePath);
Edit I posted this without reading his new edit: I see you're using Image.FromFile.
If the file does not have a valid image format or if GDI+ does not support the pixel format of the file, this method throws an OutOfMemoryException exception.
You're going to have to dispose of the Image before you can delete it.
Image.FromFile
The file remains locked until the Image is disposed.
private Image image;
in your image load function:
image = Image.FromFile("path");
picobx.Image = image;
this goes in your delete method;
image.Dispose;
File.Delete("path");
--- No longer relevant ---
If you're reading the file from a stream and converting the stream to an image. Then you try and delete the file without closing the stream you will get an IOException.
System.IO.IOException: The process cannot access the file 'File Here' because it is being used by another process..
and example of what could be causing this
StreamReader file = new StreamReader(#"C:\trans.txt");
file.ReadToEnd();
File.Delete(#"C:\trans.txt");
I was loading a Bitmap Image from a File. When I tried to save the Image to another file I got the following error "A generic error occurred in GDI+". I believe this is because the file is locked by the image object.
Ok so tried calling the Image.Clone function. This still locks the file.
hmm. Next I try loading a Bitmap Image from a FileStream and load the image into memory so GDI+ doesn't lock the file. This works great except I need to generate thumbnails using Image.GetThumbnailImage method it throws an out of memory exception. Apparently I need to keep the stream open to stop this exception but if I keep the stream open then the file remains locked.
So no good with that method. In the end I created a copy of the file. So now I have 2 versions of the file. 1 I can lock and manipulate in my c# program. This other original file remains unlocked to which I can save modifications to. This has the bonus of allowing me to revert changes even after saving them because I'm manipulating the copy of the file which cant change.
Surely there is a better way of achieving this without having to have 2 versions of the image file. Any ideas?
Well if you're looking for other ways to do what you're asking, I reckon it should work to create a MemoryStream, and read out the FileStream to it, and load the Image from that stream...
var stream = new FileStream("original-image", FileMode.Open);
var bufr = new byte[stream.Length];
stream.Read(bufr, 0, (int)stream.Length);
stream.Dispose();
var memstream = new MemoryStream(bufr);
var image = Image.FromStream(memstream);
Or something prettier to that extent.
Whether or not that's the way you should go about solving that problem, I don't know. :)
I've had a similar problem and wound up fixing it like this.
I have since found an alternative method to clone the image without locking the file. Bob Powell has it all plus more GDI resources.
//open the file
Image i = Image.FromFile(path);
//create temporary
Image t=new Bitmap(i.Width,i.Height);
//get graphics
Graphics g=Graphics.FromImage(t);
//copy original
g.DrawImage(i,0,0);
//close original
i.Dispose();
//Can now save
t.Save(path)
I had a similar problem. But I knew, that I will save the image as a bitmap-file. So I did this:
public void SaveHeightmap(string path)
{
if (File.Exists(path))
{
Bitmap bitmap = new Bitmap(image); //create bitmap from image
image.Dispose(); //delete image, so the file
bitmap.Save(path); //save bitmap
image = (Image) bitmap; //recreate image from bitmap
}
else
//...
}
Sure, thats not the best way, but its working :-)