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Intermediate License: The Code Project Open License (CPOL)
How to convert pictures on the fly (downloading & converting)By HADBI Moussa Benameur {Mozads}Explain how to make a picture converter & downloader (Only http is supported) |
VB (VB 7.x, VB), .NET (.NET, .NET 1.0, .NET 1.1, .NET 2.0, .NET 3.0), Dev Posted: 9 Mar 2008 Updated: 11 Mar 2008 Views: 10,854 Bookmarked: 18 times |
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Introduction
Hay,...this code does download pictures on background (shadow) and convert or resize them to a specific format/size. May be some guys will find how to use the background worker in this article also useful, but we dont lost focus its not our goal in this article.
Background
This code doesnt really need hard stuff to know about, may be you will need some information about asynchronous programming since im using a background worker (after all i will explain dont worry...).
Using the code
Lets start !
In our project , we will need :
The main form that will include :
*) 7 Labels: {Url, Save to, Filename, Format, ???, Height, Width}
*) 1 Combo Box : contain the different supported picture format (bmp, ico, png, wmf, jpg, tiff, gif and emf).
*) 2 command buttons : [Folder] to select a folder, and [Proceed] to download and convert our picture
*) 1 check box, may be you will need to resize your picture...who knows !!!!!!
*) 2 components : Background worker, and FolderBrowserDialog .
Well since we are using a backgound worker, we will need a class (GetFiles), and its our precious "cargot" !
HOW IT WORKS
*) First the we start by filling all information: the url from where we will grabb our picture (in my example only http server are supported, may be you can add FTP transfer), folder that will hold the file, the file name, the format of the picture, and if the set the checkbox to true (checked) the two other textboxes will permit us to enter the width/height of our resulting picture.
note : if you set the width/height to 0, the resulting picture will hold the original size (width/height)
*) When we click on proceed :
' Start the background worker, and disable the proceed button ! Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click Me.BackgroundWorker1.RunWorkerAsync() Me.Button1.Enabled = False End Sub Private Sub BackgroundWorker1_DoWork(ByVal sender As Object, ByVal e As System.ComponentModel.DoWorkEventArgs) Handles BackgroundWorker1.DoWork ' Dim MyGetFiles As Getfiles If CheckBox1.Checked Then ' being true, means that we will need to resize the picture MyGetFiles = New Getfiles(Label4.Text, TextBox1.Text, TextBox4.Text, TextBox5.Text, MyNewFormat) Else 'being false, the picture will stay as it is, but we change only the format MyGetFiles = New Getfiles(Label4.Text, TextBox1.Text, 0, 0, MyNewFormat) End If MyGetFiles.MyPictureConverter() MyGetFiles = Nothing End Sub
Now we can jump to our class :
'Properties Private MyURLex As String 'URL of our picture Private MyPATHex As String 'Path on wich the resulting picture will be saved Private MyWidthEx As Int32 = 0 'The new width of picture Private MyHeightEx As Int32 = 0 ' The new height of picture Private MyFormatEx As Imaging.ImageFormat ' The new format of the picture
as you did see in the BackgroundWorker1_DoWork sub,
there is a constructor of class [new] that helps us to set all our
private properties this remind me encapsulation concept.
Sub New(ByVal MyPath As String, ByVal MyURL As String, ByVal Height As Int32, ByVal Width As Int32, ByVal MyFormat As Imaging.ImageFormat) MyURLex = MyURL MyPATHex = MyPath MyHeightEx = Height MyWidthEx = Width MyFormatEx = MyFormat End Sub
after our properties being set, the MypictureConverter subroutine will be invoked ! what about it ?
Friend Sub MyPictureConverter()
Dim MyTarget As New Uri(MyURLex)
Dim MyMemStream As New MemoryStream 'The "picture" will be first saved to memory
'To verify that our file is intact i added this two variables
Dim MyDownData As Integer = 0
Dim FileSize As Int64
'Start the request...
Dim MyWebRequest As HttpWebRequest = WebRequest.Create(MyTarget)
'Set the response time to 5 seconds
MyWebRequest.Timeout = 5000
Dim MyWebResponse As WebResponse = MyWebRequest.GetResponse
'Get the size of the picture
FileSize = MyWebResponse.ContentLength
'Download the picture NOW !!!!
Dim MyStream As Stream = MyWebResponse.GetResponseStream
Dim MyCache(1024) As Byte
Dim MyCount As Integer = MyStream.Read(MyCache, 0, MyCache.Length)
'Store the number of bytes transfered
MyDownData = MyCount
While MyCount > 0
'Write downloaded data to memory stream
MyMemStream.Write(MyCache, 0, MyCount)
MyCount = MyStream.Read(MyCache, 0, MyCache.Length)
'Store the number of bytes transfered
MyDownData += MyCount
End While
MyMemStream.Flush()
MyMemStream.Seek(0, SeekOrigin.Begin)
MyStream.Close()
MyWebResponse.Close()
'Check if all data was well downloaded
If FileSize = MyDownData Then
'Call pictures converter
MyConverter(MyMemStream) 'What the hell this routine does come from !!!!
MyMemStream.Close()
Else
MsgBox("An error occured when downloading the file")
MyWebResponse.Close()
End If
Lets see what the hell she comes from,... MyConverter(MyMemStream)
Private Sub MyConverter(ByVal MemStream As MemoryStream)
Dim MyOriginalPic As New Bitmap(MemStream) 'This will help us to create our picture from the resulting stream (memory stream)
Dim MyFinalPic As Bitmap
'Set the width/height of the picture
If MyWidthEx = 0 Then
MyWidthEx = MyOriginalPic.Width
End If
If MyHeightEx = 0 Then
MyHeightEx = MyOriginalPic.Height
End If
'Convert...
Try
' Now create the new bitmap, and set the width/height
MyFinalPic = New Bitmap(MyOriginalPic, MyWidthEx, MyHeightEx)
' Save the resulting new picture to the path, and new format
MyFinalPic.Save(MyPATHex, MyFormatEx)
' *.tiff, *.ico, *.bmp, *.jpg, *.png,
Catch ex As Exception
MsgBox(ex.Message & "/" & Err.Number & "/" & Err.Description)
End Try
End Sub
And now that all is finished, we enable the [Proceed] command button ! and we can try to download again. I notice that this code does support only HTTP/file transfer...later i will add a routine that support other kind of transfer such FTP !
Points of Interest
I guess its better to act like this, since now our computer comes up with a very big physical memory ( in my example 1024 MB) so we can let the Hard disk Rest In Peace...for a while...History
On the next version, i will try to add some useful graphical optimisation / modification.| You must Sign In to use this message board. | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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Last Updated: 11 Mar 2008 Editor: |
Copyright 2008 by HADBI Moussa Benameur {Mozads} Everything else Copyright © CodeProject, 1999-2008 Web09 | Advertise on the Code Project |