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From: John Hewson <john@jahewson.com>
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Subject: Re: Rendering PDImageXObject
Date: Thu, 13 Aug 2015 20:59:02 -0700
References: <DC902F4011063E4394F5F7D12175834756FAE6D0@EXCDB.ILSOS.ORG>
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To: users@pdfbox.apache.org
In-Reply-To: <DC902F4011063E4394F5F7D12175834756FAF97D@EXCDB.ILSOS.ORG>

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> On 13 Aug 2015, at 08:15, Kirk, Kenneth <Kkirk@ILSOS.NET> wrote:
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> 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=E2=80=99t 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.

Ok, to recap: you=E2=80=99re extracting an image which is drawn on a PDF =
page and you=E2=80=99re wanting to know the size of the image relative =
to the page. The embedded image itself is at a high resolution, so is =
much bigger than the page if drawn without the appropriate scale.

First of all, if your images are full page sized then you can simply =
render the page with PDFBox at your chosen DPI and use the resulting =
image instead.

Otherwise, you=E2=80=99ll need to obtain the current transform matrix =
(CTM) which is being used at the point that the image is drawn. If you =
look at the ExtractImages example which ships with PDFBox, then in the =
drawImages override you can add the following line to fetch this:

Matrix ctm =3D getGraphicsState().getCurrentTransformationMatrix();

That matrix contains the scaling for the image, as well as any rotation =
and skew. For x and y scalling, you want getScalingFactorX() and =
getScalingFactorY().

Hope that helps,

=E2=80=94 John

> -----Original Message-----
> From: John Hewson [mailto:john@jahewson.com]=20
> Sent: Wednesday, August 12, 2015 7:24 PM
> To: users@pdfbox.apache.org
> Subject: Re: Rendering PDImageXObject
>=20
> Ok, that makes sense. Which part are you having a problem with?
>=20
> =E2=80=94 John
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>> On 12 Aug 2015, at 07:31, Kirk, Kenneth <Kkirk@ILSOS.NET> wrote:
>>=20
>> 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.
>>=20
>> -----Original Message-----
>> From: John Hewson [mailto:john@jahewson.com]=20
>> Sent: Tuesday, August 11, 2015 9:11 PM
>> To: users@pdfbox.apache.org
>> Subject: Re: Rendering PDImageXObject
>>=20
>>=20
>>> On 11 Aug 2015, at 08:19, Kirk, Kenneth <Kkirk@ILSOS.NET> wrote:
>>>=20
>>> John
>>>=20
>>> 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.
>>=20
>> I=E2=80=99m 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?
>>=20
>> =E2=80=94 John
>>=20
>>> -----Original Message-----
>>> From: John Hewson [mailto:john@jahewson.com]=20
>>> Sent: Monday, August 10, 2015 1:38 PM
>>> To: users@pdfbox.apache.org
>>> Subject: Re: Rendering PDImageXObject
>>>=20
>>>=20
>>>> On 10 Aug 2015, at 05:58, Kirk, Kenneth <Kkirk@ILSOS.NET> wrote:
>>>>=20
>>>> 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.
>>>>=20
>>>=20
>>> You can draw the image with a scale of 72 / 200, in other words:
>>>=20
>>> double dpi =3D 200; // you=E2=80=99ll want to fetch this from the =
tiff content.drawImage(image, x, y, image.getWidth() * 72 / dpi, =
image.getHeight() * 72 / dpi;
>>>=20
>>> =E2=80=94 John
>>> =
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copy, distribute or use this email or the information contained in it =
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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.=20
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Illinois Secretary of State.=20
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