We Keep Coding

How to use OCR to read text from image

I'm trying to use IronOCR to read the text from an image. I manually download their dll and include in my project and follow the example that they provided on their website. However, there is no text return at all. Even I'm trying on different file or their sample image also no result. Is there any step that I'm missing?
Here I attach the image that i'm using to try:myImage

Try the following code with the latest version of IronOCR (currently 2021.2.1) which was updated to use Tesseract 4 & 5. Returned a perfect result on your example image.
var Ocr = new IronTesseract();
using (var Input = new OcrInput(#"F:\input_image.png"))
{
Input.Deskew();
var Result = Ocr.Read(Input);
}
Deskew filter gave the best results but there are other that may be useful listed here:
https://ironsoftware.com/csharp/ocr/examples/ocr-image-filters-for-net-tesseract/

Accessing Images in PowerPoint file via VSTO Add-In (C#)

I am trying to build a PowerPoint add-in that will allow me to do a one-click optimization of the current presentation by removing unused master slides and converting huge 24-bit PNG files to slightly-compressed JPGs.
I have the first part handled already, and now I'm working on the images. Although I can easily find the Shape object containing the image, I cannot find a way to access the source image through the managed API. At best, I can copy the shape to the clipboard, which does give me the image but in a different format (MemoryBmp).
using PPTX = Microsoft.Office.Interop.PowerPoint;
...
foreach (PPTX.Slide slide in Globals.ThisAddIn.Application.ActivePresentation.Slides)
{
foreach (PPTX.Shape shape in slide.Shapes)
{
if (shape.Type == MsoShapeType.msoPicture)
{
// Now, how can I access the source image contained within this shape?
// I -can- copy it via the clipboard, like this:
shape.Copy();
System.Drawing.Image image = Clipboard.GetImage();
// ...but image's format reflects a MemoryBmp ImageFormat, as noted here:
// https://referencesource.microsoft.com/#System.Drawing/commonui/System/Drawing/Advanced/ImageFormat.cs
// ...which doesn't help me determine if the source image is something that should be optimized.
}
}
}
Obviously, I can get to the images directly via other methods (e.g. accessing the contents of the file as a ZIP, or using OpenXML SDK), but I'm trying to perform all the steps from within the already-opened presentation (which means I can't update the open file). Any thoughts on how I can do this?

You could use a Microsoft.Office.Interop.PowerPoint.Shape Export function.
void Export(string PathName, PpShapeFormat Filter, int ScaleWidth = 0, int ScaleHeight = 0, PpExportMode ExportMode = PpExportMode.ppRelativeToSlide)
There is a very little documentation of this function.
I've found it in the Shape interface definition.
So your code would look something like:
shape.Export(<some_file>, PpShapeFormat.ppShapeFormatPNG);
More info on MSDN

Onenote OCR capabilities in a desktop software

Is there an API to use Onenote OCR capabilities to recognise text in images automatically?

If you have OneNote client on the same machine as your program will execute you can create a page in OneNote and insert the image through the COM API. Then you can read the page in XML format which will include the OCR'ed text.
You want to use
Application.CreateNewPage to create a page
Application.UpdatePageContent to insert the image
Application.GetPageContent to read the page content and look for OCRData and OCRText elements in the XML.
OneNote COM API is documented here: http://msdn.microsoft.com/en-us/library/office/jj680120(v=office.15).aspx

When you put an image on a page in OneNote through the API, any images will automatically be OCR'd. The user will then be able to search any text in the images in OneNote. However, you cannot pull the image back and read the OCR'd text at this point.
If this is a feature that interests you, I invite you to go to our UserVoice site and submit this idea: http://onenote.uservoice.com/forums/245490-onenote-developers
update: vote on the idea: https://onenote.uservoice.com/forums/245490-onenote-developer-apis/suggestions/10671321-make-ocr-available-in-the-c-api
-- James

There is a really good sample of how to do this here:
http://www.journeyofcode.com/free-easy-ocr-c-using-onenote/
The main bit of code is:
private string RecognizeIntern(Image image)
{
this._page.Reload();
this._page.Clear();
this._page.AddImage(image);
this._page.Save();
int total = 0;
do
{
Thread.Sleep(PollInterval);
this._page.Reload();
string result = this._page.ReadOcrText();
if (result != null)
return result;
} while (total++ < PollAttempts);
return null;
}

As I will be deleting my blog (which was mentioned in another post), I thought I should add the content here for future reference:
Usage
Let's start by taking a look on how to use the component: The class OnenoteOcrEngine implements the core functionality and implements the interface IOcrEngine which provides a single method:
public interface IOcrEngine
{
string Recognize(Image image);
}
Excluding any error handling, it can be used in a way similar to the following one:
using (var ocrEngine = new OnenoteOcrEngine())
using (var image = Image.FromFile(imagePath))
{
var text = ocrEngine.Recognize(image);
if (text == null)
Console.WriteLine("nothing recognized");
else
Console.WriteLine("Recognized: " + text);
}
Implementation
The implementation is far less straight-forward. Prior to Office 2010, Microsoft Office Document Imaging (MODI) was available for OCR. Unfortunately, this no longer is the case. Further research confirmed that OneNote's OCR functionality is not directly exposed in form of an API, but the suggestions were made to manually parse OneNote documents for the text (see Is it possible to do OCR on a Tiff image using the OneNote interop API? or need a document to extract text from image using onenote Interop?. And that's exactly what I did:
Connect to OneNote using COM interop
Create a temporary page containing the image to process
Show the temporary page (important because OneNote won't perform the OCR otherwise)
Poll for an OCRData tag containing an OCRText tag in the XML code of the page.
Delete the temporary page
Challenges included the parsing of the XML code for which I decided to use LINQ to XML. For example, inserting the image was done using the following code:
private XElement CreateImageTag(Image image)
{
var img = new XElement(XName.Get("Image", OneNoteNamespace));
var data = new XElement(XName.Get("Data", OneNoteNamespace));
data.Value = this.ToBase64(image);
img.Add(data);
return img;
}
private string ToBase64(Image image)
{
using (var memoryStream = new MemoryStream())
{
image.Save(memoryStream, ImageFormat.Png);
var binary = memoryStream.ToArray();
return Convert.ToBase64String(binary);
}
}
Note the usage of XName.Get("Image", OneNoteNamespace) (where OneNoteNamespace is the constant "http://schemas.microsoft.com/office/onenote/2013/onenote" ) for creating the element with the correct namespace and the method ToBase64 which serializes an GDI-image from memory into the Base64 format. Unfortunately, polling (See What is wrong with polling? for a discussion of the topic) in combination with a timeout is necessary to determine whether the detection process has completed successfully:
int total = 0;
do
{
Thread.Sleep(PollInterval);
this._page.Reload();
string result = this._page.ReadOcrText();
if (result != null)
return result;
} while (total++ < PollAttempts);
Results
The results are not perfect. Considering the quality of the images, however, they are more than satisfactory in my opinion. I could successfully use the component in my project. One issue remains which is very annoying: Sometimes, OneNote crashes during the process. Most of the times, a simple restart will fix this issue, but trying to recognise text from some images reproducibly crashes OneNote.
Code / Download
Check out the code at GitHub

not sure about OCR, but the documentation site for onenote API is this
http://msdn.microsoft.com/en-us/library/office/dn575425.aspx#sectionSection1

Can a PDF be converted to a vector image format that can be printed from .NET?

We have a .NET app which prints to both real printers and PDF, currently using PDFsharp, although that part can be changed if there's a better option. Most of the output is generated text or images, but there can be one or more pages that get appended to the end. That page(s) are provided by the end-user in PDF format.
When printing to paper, our users use pre-printed paper, but in the case of an exported PDF, we concatenate those pages to the end, since they're already in PDF format.
We want to be able to embed those PDFs directly into the print stream so they don't need pre-printed paper. However, there aren't really any good options for rendering a PDF to a GDI page (System.Drawing.Graphics).
Is there a vector format the PDF could be converted to by some external program, that could rendered to a GDI+ page without being degraded by conversion to a bitmap first?

In an article titled "How To Convert PDF to EMF In .NET," I have shown how to do this using our PDFOne .NET product. EMFs are vector graphics and you can render them on the printer canvas.
A simpler alternative for you is PDF overlay explained in another article titled "PDF Overlay - Stitching PDF Pages Together in .NET." PDFOne allows x-y offsets in overlays that allows you stitch pages on the edges. In the article cited here, I have overlaid the pages one over another by setting the offsets to zero. You will have set it to page width and height.
DISCLAIMER: I work for Gnostice.

Ghostscript can output PostScript (which is a vector file) which can be directly sent to some types of printers. For example, if you're using an LPR capable printer, the PS file can be directly set to that printer using something like this project: http://www.codeproject.com/KB/printing/lpr.aspx
There are also some commercial options which can print a PDF (although I'm not sure if the internal mechanism is vector or bitmap based), for example http://www.tallcomponents.com/pdfcontrols2-features.aspx or http://www.tallcomponents.com/pdfrasterizer3.aspx

I finally figured out that there is an option that addresses my general requirement of embedding a vector format into a print job, but it doesn't work with GDI based printing.
The XPS file format created by Microsoft XPS Writer print driver can be printed from WPF, using the ReachFramework.dll included in .NET. By using WPF for printing instead of GDI, it's possible to embed an XPS document page into a larger print document.
The downside is, WPF printing works quite a bit different, so all the support code that directly uses stuff in the Sytem.Drawing namespace has to be re-written.
Here's the basic outline of how to embed the XPS document:
Open the document:
XpsDocument xpsDoc = new XpsDocument(filename, System.IO.FileAccess.Read);
var document = xpsDoc.GetFixedDocumentSequence().DocumentPaginator;
// pass the document into a custom DocumentPaginator that will decide
// what order to print the pages:
var mypaginator = new myDocumentPaginator(new DocumentPaginator[] { document });
// pass the paginator into PrintDialog.PrintDocument() to do the actual printing:
new PrintDialog().PrintDocument(mypaginator, "printjobname");
Then create a descendant of DocumentPaginator, that will do your actual printing. Override the abstract methods, in particular the GetPage should return DocumentPages in the correct order. Here's my proof of concept code that demonstrates how to append custom content to a list of Xps documents:
public override DocumentPage GetPage(int pageNumber)
{
for (int i = 0; i < children.Count; i++)
{
if (pageNumber >= pageCounts[i])
pageNumber -= pageCounts[i];
else
return FixFixedPage(children[i].GetPage(pageNumber));
}
if (pageNumber < PageCount)
{
DrawingVisual dv = new DrawingVisual();
var dc = dv.Drawing.Append();
dc = dv.RenderOpen();
DoRender(pageNumber, dc); // some method to render stuff to the DrawingContext
dc.Close();
return new DocumentPage(dv);
}
return null;
}
When trying to print to another XPS document, it gives an exception "FixedPage cannot contain another FixedPage", and a post by H.Alipourian demonstrates how to fix it: http://social.msdn.microsoft.com/Forums/da/wpf/thread/841e804b-9130-4476-8709-0d2854c11582
private DocumentPage FixFixedPage(DocumentPage page)
{
if (!(page.Visual is FixedPage))
return page;
// Create a new ContainerVisual as a new parent for page children
var cv = new ContainerVisual();
foreach (var child in ((FixedPage)page.Visual).Children)
{
// Make a shallow clone of the child using reflection
var childClone = (UIElement)child.GetType().GetMethod(
"MemberwiseClone", BindingFlags.Instance | BindingFlags.NonPublic
).Invoke(child, null);
// Setting the parent of the cloned child to the created ContainerVisual
// by using Reflection.
// WARNING: If we use Add and Remove methods on the FixedPage.Children,
// for some reason it will throw an exception concerning event handlers
// after the printing job has finished.
var parentField = childClone.GetType().GetField(
"_parent", BindingFlags.Instance | BindingFlags.NonPublic);
if (parentField != null)
{
parentField.SetValue(childClone, null);
cv.Children.Add(childClone);
}
}
return new DocumentPage(cv, page.Size, page.BleedBox, page.ContentBox);
}
Sorry that it's not exactly compiling code, I just wanted to provide an overview of the pieces of code necessary to make it work to give other people a head start on all the disparate pieces that need to come together to make it work. Trying to create a more generalized solution would be much more complex than the scope of this answer.

While not open source and not .NET native (Delphi based I believe, but offers a precompiled .NET library), Quick PDF can render a PDF to an EMF file which you could load into your Graphics object.

Extract Data from .PDF files

I need to extract data from .PDF files and load it in to SQL 2008.
Can any one tell me how to proceed??

Here is an example of how to use iTextSharp to extract text data from a PDF. You'll have to fiddle with it some to make it do exactly what you want, I think it's a good outline. You can see how the StringBuilder is being used to store the text, but you could easily change that to use SQL.
static void Main(string[] args)
{
PdfReader reader = new PdfReader(#"c:\test.pdf");
StringBuilder builder = new StringBuilder();
for (int x = 1; x <= reader.NumberOfPages; x++)
{
PdfDictionary page = reader.GetPageN(x);
IRenderListener listener = new SBTextRenderer(builder);
PdfContentStreamProcessor processor = new PdfContentStreamProcessor(listener);
PdfDictionary pageDic = reader.GetPageN(x);
PdfDictionary resourcesDic = pageDic.GetAsDict(PdfName.RESOURCES);
processor.ProcessContent(ContentByteUtils.GetContentBytesForPage(reader, x), resourcesDic);
}
}
public class SBTextRenderer : IRenderListener
{
private StringBuilder _builder;
public SBTextRenderer(StringBuilder builder)
{
_builder = builder;
}
#region IRenderListener Members
public void BeginTextBlock()
{
}
public void EndTextBlock()
{
}
public void RenderImage(ImageRenderInfo renderInfo)
{
}
public void RenderText(TextRenderInfo renderInfo)
{
_builder.Append(renderInfo.GetText());
}
#endregion
}

Imagine if you asked this question. How can I load data from arbitrary text files into a SQL table. The challenge isn't opening the text file and reading it, its getting meaningful data out of the files automatically.
So you can use either iText or pdfSharp to read the PDF files, but its the getting meaningful data out that's going to be the challenge.

what you need to do is to use a tool to extract the text from PDF first and then read the file into a binary reader .. then store it into your database .. for extracting the text there are several tools to use. the first to mention are:
iTextsharp which is a Library that can be downloaded and used to do extensive work and in-depth edits and builds when dealing with PDF documents, and there are a lot of examples available online along with a full book that explains the ins and outs of itThe second tool is Adobe PDF iFilter which is a tool from adobe to deal with PDF modifications and manipulation.
Also Foxit iFilter also is a similar assembly that can do just what u r asking for!
PDF Boxwill also serve you!
these are the most well known and well documented ones!
check the following examples:
try the following examples on code project:
Parsing PDF files in .NET using PDFBox and IKVM.NET.A simple class to extract plain text from PDF documents with ITextSharpUsing the IFilter interface to extract text from various document types A parser for PDF Forms written in C#.NET
These do the job and they ain't hard to understand. Hope they help you :-)
A final note: as for me, i would iTextSharp as it's the most well documented library with most available examples.

If you mean metadata, try this question (first answer)
Read/Modify PDF Metadata using iTextSharp
You'll have to do the database stuff yourself though.