Develop Reference

How to add image background to pdf for every page?

I'm trying to set a background to a pdf and managed to set it with an image my pdf has a big table so the pages are added automatically not with the Document.NewPage() method so the image background is set only on the first page. This is the code that adds the background:
Image backImg = Image.GetInstance(#"D:\websites\DIS\bugs\130208\A4.png");
backImg.SetAbsolutePosition(0, 0);
backImg.Alignment = Image.UNDERLYING;
var doc = new Document(pageSize);
PdfWriter pdfWriter = PdfWriter.GetInstance(doc, new FileStream(filePath, FileMode.Create));
doc.Open();
doc.Add(backImg);
...
creating a big table
and not using the doc.NewPage() method. Do I have to loop throw every page and add the background image at the end before closing the doc, but how do I put it in the background not on top of the other elements?

Whenever you want to apply something to every page, you should use page events, more specifically PdfPageEvent.onEndPage(), to do it. You can find samples for its usage by keyword Page events > onEndPage --- these samples are taken from iText in Action 2nd Edition. The samples mainly add footers and headers while you want to add background graphics.
Be aware that you shouldn't add content to the Document instance here but instead directly to the PdfWriter, and as you want the image to be under the page content , not above it, you will need to use PdfWriter.getDirectContentUnder() like in the sample Stationery and not PdfWriter.getDirectContent() like in the other samples.
PS: The analogous samples for .Net can be found here.
PPS: The sample ImageDirect.java / ImageDirect.cs shows how to add an image to some direct content which might be the information missing here.

go for
PdfPageEvent.onStartPage()
. In this event, write your code to insert the image (as you are doing it). What it will do is that as soon as a new page is created, it will add the image to it and then the content over it; giving a watermark effect.

adding images to an HTML Canvas Generated by C#

Hello so I have an interesting question for everyone. I have a WPF application that generates an html preview of a report based on Database data and user input. My currently dilemma is that I have a HTML canvas that is created by C# as follows:
Canvas myCanvas = new Canvas();
myCanvas.Name = "cvsMyCanvas";
myCanvas.width = userDefinedByTtextBox;
myCanvas.height = userDefinedByTtextBox;
myCanvas.Visibility = Visibility.Collapsed //Don't show the canvas just yet
My question is how do I get an image that I have saved locally to the computer on the canvas in a specific position. (i.e. A HTML Image tag object that is generated by C# and use the move to functionality)
(This is a rough example of how I think it should work but this is what I need the help on)
Example:
string htmlImage = "<img id=\"myImage\" src=\"C:\\Temp\\img.png\">";
htmlImage.moveTo(x,y);
...again the above code is an example of what it is I am trying to do. If anyone could help me out that would be great! Also if I did not provide enough information please let me know and I will let provide it.
There seems to be some confusion on what it is I am trying to do, it is most likely my fault do to lack of explanation so allow me to elaborate more. I have images saved in a folder in my temp directory I. I am running a WPF application that has a WebBrowser control that I am using to display HTML. The HTML that is used in that WebBrowser is created in the C# code behind. I am trying to create a canvas that is displayed in the WebBrowser with the images that I have saved in my temp folder. The code I have provided above apparently will not work for what I am trying to accomplish because there is no way to create a canvas in C# and use it in HTML. Let me know if this helps shed some light on this predicament or if even more explanation is required.

If you want to generate HTML5 code from your C#, the HTML code to generate should look like that:
context = canvas.getContext('2d');
var image = new Image();
image.src = <your path>;
image.onload = function() {
context.drawImage(image, x, y, w, y);
}
Then, just store it in the String or StringBuilder

drawing lines on screen?

I've been reading through a few asp.net articles, and attempting some code, but I think I may be confused. Can you or can you not draw lines on the screen with code on a ASP.NET webform using c#?
If so, can anyone direct me to some examples?

You cannot directly draw on a webform. You may draw on the image and then embed it on your webform (like any other image).

You can make a canvas and then you can draw whatever you want to draw on it.But direct drawing is impossible.

If you are fine with HTML5 you can try lineto Javascript method:
<script>
context.lineTo(100, 200);
</script>
Please refer # following link for more details:
http://www.html5canvastutorials.com/tutorials/html5-canvas-lines/

Not sure what you mean by "draw a line" but if you are using a web browser you need some kind of HTML object to display this "line". If all you need is a horizontal line you can just add a HR html tag and use CSS toy stylize it. You can also include this line in an image or HTML5 Canvas.

Because there is not screen for your server side code. Your code generates HTML, JavaScript etc. and then browser uses that content to render it on the client screen. So your options are to generate image (draw all that you need) in server side code and send it to the browser, or you can use JavaScript and send browser instructions how to draw lines.

You could probably create a new image using the System.Drawing namespace classes and then do something like dynamically load it into an <img /> tag...but depending on what you're trying to accomplish it may be far easier to either use a JavaScript library of some sort or to use some sort of very simple line image and tweak the length/height using css.
More detail would be needed to understand what you're trying to do. As others have pointed out though, there's no direct way for your C# code to interact with the page. You'd have to have something on the page like an img tag and then set it's source to a C# file like a handler (.ashx). In that handler you could generate the image and then set the response content type as image/jpg and write the raw bytes to the response stream...
Again though, that seems like overkill for something that could be accomplished with CSS or javascript.

how to resize a picture programatically and add it to the web site

Hi there
I am working with visual web developer and would a) like to know how I could programatcally add a picture to the website, instead of going to Website and then add existing item. The idea I have is to upload the picture using the file upload control but then I want to have it added so that it can be accessed using a gridview.
b)I would also like to know how to size the picture using C# code obviously so that is displayed at the correct size.
best regards
arian

here is a full project with source code to manipulate images, including resize.
http://www.codeproject.com/KB/web-image/ASPImaging1.aspx
And a sample code only for resize
http://weblogs.asp.net/gunnarpeipman/archive/2009/04/02/resizing-images-without-loss-of-quality.aspx

You can use GetThumbnailImage to easily create a smaller verson of the uploaded image. The code looks something like (it's free typed without a compiler, so there may be some errors):
System.Drawing.Image pic = new System.Drawing.Bitmap(sourceFilename);
System.Drawing.Image thumb = pic.GetThumbnailImage(targetXSize,targetYSize,
new System.Drawing.Image.GetThumbnailImageAbort(this.GetThumbnailImageAbort),
IntPtr.Zero);
thumb.Save(thumbPathName);
I believe the Image implements IDisposable, so you need to remember to Dispose of them when you're done.
The abort parameter can be a function that simply does this (can't remember off the top of my head when it gets called):
bool GetThumbnailImageAbort() {
return false;
}

Render HTML as an Image

I'm generating a coupon based on dynamic input and a cropped image, and I'm displaying the coupon using ntml and css right now, the problem is, printing this has become an issue because of how backgrounds disappear when printing and other problems, so I think the best solution would be to be able to generate an image based on the html, or set up some kind of template that takes in strings and an image, and generates an image using the image fed in as a background and puts the coupon information on top.
Is there anything that does this already?
This is for an ASP.NET 3.5 C# website!
Thanks in advance.
edit: It'd be great if the output could be based on the HTML input, as the coupon is designed by manipulating the DOM using jQuery and dragging stuff around, it all works fine, it's just when it comes to the printing (to paper) it has z-indexing issues.

What you can do is create an aspx page that changes the response type to be in the format you want and then put the image into the stream. I created a barcode generator that does a similar thing. Excluding all the formalities of generating the image, you'll Page_Load will look something like this:
Bitmap FinalBitmap = new Bitmap();
MemoryStream msStream = new MemoryStream();
strInputParameter == Request.Params("MagicParm").ToString()
// Magic code goes here to generate your bitmap image.
FinalBitmap.Save(msStream, ImageFormat.Png);
Response.Clear();
Response.ContentType = "image/png";
msStream.WriteTo(Response.OutputStream);
if ((FinalBitmap != null)) FinalBitmap.Dispose();
and that's it! Then all you have to do in your image is set the URL to be something like RenderImage.aspx?MagicParm=WooHoo or whatever you need. That way you can have it render whatever you want to specify.

You can render html to a bitmap using the WebBrowser control in either a winforms or console application.
An example of this can be found here: http://www.wincustomize.com/articles.aspx?aid=136426&c=1
The above example can be modified to run in ASP.Net by creating a new STAThread and performing an Application.Run on it to start a new message loop.

PHP/Ruby Alternative
If you have accessed this question and are actually looking for soething that will work without Windows, you can try the KHTML library: http://wiki.goatpr0n.de/projects/khtmld
The website has a ridiculous name I admit, but I can assure you it is genuine. Other related pages are: the sourceforge page http://khtml2png.sourceforge.net/

Try PDFSharp...it's not exactly a "take this HTML and make a PDF" but with a small amout of fiddling you can easily make a PDF out of the info you are using to make the HTML.

MARKUP ONLY ALTERNATE SOLUTION
Use SVG and XSLT to transform the html data into an image that can be rendered/saved/etc.
I'll admit that at first it was tedious getting this to work because of all of the coordinates, but well worth the effort once it is running.

There is a very powerful image creation library called GD which I often use with PHP.
I am led to believe there is a wrapper for this library that ASP programmers can use. Try this

Unless the "other problems" are pretty severe, couldn't you just instruct your users to turn on Background Images when printing?
In any case, I'd default to serving a PDF rather than an image, doubly so since it is intended for print.

Just set up your css properly, so that you have a css file targeted at the print medium. It is pretty easy to guarantee that the coupon will always be legible, without worrying about whether they have bg images on or not. Needlesly moving to an image doesn't make any sense, unless there is some reason you don't want it to be machine readable.

I haven't tried to myself, but you should be able to render HTML into an image by using the WebBrowser control and the DrawToBitmap() method inherited from the base Control class.
UPDATE: I tried this myself and there are some caveats. The WebBrowser control doesn't seem to render the web page until the control is show, so the WebBrowser needs to be in a Form and the Form must be shown for the HTML to be rendered and the DocumentCompleted event to be raised.