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From "Kirk, Kenneth" <Kk...@ILSOS.NET>
Subject RE: Rendering PDImageXObject
Date Thu, 13 Aug 2015 15:15:36 GMT
When I create a PDF page and draw the image onto the page without any scaling applied to the
image, it is drawn at the DPI of the tiff, 200 DPI in most instances.  Later when I retrieve
the PDFs and encounter a PDF page has a image drawn on to it I won't know what DPI was used
to drawn the image on the page if it didn’t come from one of my applications.  When I render
the image using defaults it is rendered at 72 DPI which is the PDF default.  So if the iamge
was original drawn at 200 DPI it would look larger than it really is.  No problem for screen
viewing but a big problem for filming where space is at finite.

-----Original Message-----
From: John Hewson [mailto:john@jahewson.com] 
Sent: Wednesday, August 12, 2015 7:24 PM
To: users@pdfbox.apache.org
Subject: Re: Rendering PDImageXObject

Ok, that makes sense. Which part are you having a problem with?

— John

> On 12 Aug 2015, at 07:31, Kirk, Kenneth <Kkirk@ILSOS.NET> wrote:
> 
> I'm doing both.  I provide a service that takes tiff files from one of the various processes
we use to generate official documents and converts them to PDFs so they can be stored in a
document management system.  Then for archival purposes I have to take selected documents
from the document management system and convert them back to tiff so they will run through
the software/hardware that converts them to microfilm for a disaster recovery policy requirement.
> 
> -----Original Message-----
> From: John Hewson [mailto:john@jahewson.com] 
> Sent: Tuesday, August 11, 2015 9:11 PM
> To: users@pdfbox.apache.org
> Subject: Re: Rendering PDImageXObject
> 
> 
>> On 11 Aug 2015, at 08:19, Kirk, Kenneth <Kkirk@ILSOS.NET> wrote:
>> 
>> John
>> 
>> How would I know what DPI the image was drawn with?  Some of the PDF pages come from
source outside of my control but I have to extract them just the same.
> 
> I’m confused, you said you were converting TIFFs to PDF but now you mention PDF pages
from external sources? Are you reading the PDFs or writing them? Did you mean that the TFF
images come from an external source?
> 
> — John
> 
>> -----Original Message-----
>> From: John Hewson [mailto:john@jahewson.com] 
>> Sent: Monday, August 10, 2015 1:38 PM
>> To: users@pdfbox.apache.org
>> Subject: Re: Rendering PDImageXObject
>> 
>> 
>>> On 10 Aug 2015, at 05:58, Kirk, Kenneth <Kkirk@ILSOS.NET> wrote:
>>> 
>>> I have a situation that maybe someone has already solved in a more efficient
manner.  When converting a tiff image to PDF I use the drawImage method of the PDPageContentStream.
 The tiff image has a resolution of 200 DPI which is 1700x2200.  When PDFRenderer renders
this image from the resulting PDF page  it does so at the PDF default of 72 DPI which logically
translates to page 23 inches by 30 inches when applied to the original iamge size of 1700x2200.
 Since I don't know after the fact what DPI a image object on PDF page was drawn at I came
up with down scaling the image at PDF creation time to 72 DPI.  I'm sure there must a better
way one of you computer science PHDs have come up with.
>>> 
>> 
>> You can draw the image with a scale of 72 / 200, in other words:
>> 
>> double dpi = 200; // you’ll want to fetch this from the tiff content.drawImage(image,
x, y, image.getWidth() * 72 / dpi, image.getHeight() * 72 / dpi;
>> 
>> — John
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Disclaimer - This email and any files transmitted with it are confidential and contain privileged
or copyright information. You must not present this message to another party without gaining
permission from the sender. If you are not the intended recipient you must not copy, distribute
or use this email or the information contained in it for any purpose other than to notify
the Office of the Illinois Secretary of State. 

If you have received this message in error, please notify the sender immediately, and delete
this email from your system. Any views expressed in this message are those of the individual
sender, except where the sender specifically states them to be the views of the Office of
the Illinois Secretary of State. 
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