Render a page in a correct DPI
Printed From: Debenu Quick PDF Library - PDF SDK Community Forum
Category: For Users of the Library
Forum Name: I need help - I can help
Forum Description: Problems and solutions while programming with the Debenu Quick PDF Library and Debenu PDF Viewer SDK
URL: http://www.quickpdf.org/forum/forum_posts.asp?TID=1763
Printed Date: 02 Jul 25 at 1:35PM
Software Version: Web Wiz Forums 11.01 - http://www.webwizforums.com
Topic: Render a page in a correct DPI
Posted By: moi meme
Subject: Render a page in a correct DPI
Date Posted: 09 Mar 11 at 2:20PM
Hello,
I open and render each page in a byte[] to OCRize them.
But I don't really understand what I need to set as rendered DPI.
byte[] bytes = Engine.RenderPageToString(RenderedPdfDpi, pageIdx + 1, 0);
If I set 300 for example, and my pdf was in 96, I have a *3 zoom, which is very time consuming for my OCR. At the contrary, if I set 150 and my pdf was in 300, I have bad recognition results.
My PDF are simple multi pages images (like a TIF), so I thought about selecting the first image of each page, and reproduce the same DPI. But this do not work:
Engine.SelectPage(pageIdx + 1);
Engine.SelectImage(Engine.GetImageID(1));
Can somebody help me ?
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Replies:
Posted By: moi meme
Date Posted: 09 Mar 11 at 2:24PM
Note:
To create the document, I simply load a PDF file with:
Engine.LoadFromFile(filename);
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Posted By: moi meme
Date Posted: 09 Mar 11 at 2:31PM
Hum... Now, the image selection works (I must have confused myself).
But I'm still unable to get the resolution of the image: ImageHorizontalResolution returns 0.
code:
Engine.LoadFromFile(filename);
Engine.SelectPage(pageIdx + 1);
int imgID = Engine.GetImageID(pageIdx + 1)
Engine.SelectImage(imgID);
int resH = Engine.ImageHorizontalResolution();
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Posted By: moi meme
Date Posted: 09 Mar 11 at 3:01PM
Ok I found :>
I only needed to set the right resolution to the rendered bitmap:
RenderedPdfDpi = 300;
byte[] bytes = Engine.RenderPageToString(RenderedPdfDpi, pageIdx + 1, 0);
Bitmap bitmap = new Bitmap(new MemoryStream(bytes));
bitmap.SetResolution(RenderedPdfDpi, RenderedPdfDpi);
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