[Blindmath] Extracting bitmap images from pdf files

Richard Baldwin baldwin at dickbaldwin.com
Fri Jan 27 20:06:34 UTC 2012 

Maureen,

Does the Tiger emboss the image in color, or does it emboss the image with
different dot heights of which you can probably distinguish among three or
four different heights using your fingers?

The conventional wisdom in the sonar world is that an experienced sonar
operator can visually distinguish only about seven shades of gray. I would
imagine that an experienced Tiger user would be able to distinguish among
three or four different dot heights with the fingers -- maybe more, but
clearly not 16 million. I may be wrong, but I believe that the Tiger
attempts to produce 8 different dot heights.

That is what I meant when I referred to three or four shades of gray in my
earlier post. Converting from an image with 16 million colors to a tactile
image with three or four distinguishable dot heights is analogous to
converting the image from 16 million colors to three or four shades of gray.

Dick Baldwin

On Fri, Jan 27, 2012 at 1:56 PM, Richard Baldwin <baldwin at dickbaldwin.com>wrote:

> In a previous post I wrote:
>
> "By the way, I don't know how a blind person would carry out the second
> of the following two steps in John's procedure:
>
> * import the PDF into IVEO Creator Pro.
> * Check the PDF to find which pages have images of interest and emboss
> those
> pages.
>
> It seems that checking the pdf to find which pages have images would be
> similar to checking a screen shot of a page to find and crop the image. It
> seems that you would need to be able to see the pdf on the IVEO screen to
> know if it contains an image. I am working with pdf files containing
> anywhere between 30 and 80 pages. Embossing every page in order to identify
> the pages that contain images would not be practical."
>
> I have learned how a blind person could find the pages containing the
> images in a pdf file without having to see the screen. Here is one
> procedure for doing that.
>
> When you import a pdf file into Creator Pro, a set of SVG files is
> automatically created in the folder than contains the pdf file. There is
> one SVG file for each page in the pdf file. The file names indicate the pdf
> page number except that pages in a pdf file are typically numbered
> beginning with 1 while the file numbers produced by Creator Pro begin with
> 0. Thus, file number 0 will probably correspond to page 1 in the pdf
> document.
>
> Read the pdf file in your preferred pdf file reader. If from the pdf text,
> you can determine which pages in the pdf file contain images of interest,
> you can record those page numbers using whatever method you use to record
> information of that sort.
>
> Then you can import the pdf file into Creator Pro, producing the set of
> SVG files described above. Then you can open the SVG files that contain
> interesting images in your IVEO viewer software, emboss the pages, and
> proceed as John explained in an earlier post.
>
> Dick Baldwin
>
>
> On Fri, Jan 27, 2012 at 12:47 PM, Richard Baldwin <baldwin at dickbaldwin.com
> > wrote:
>
>> Michael wrote " There is one option I am aware of for a blind person to
>> do this independently, IVEO like John suggested,"
>>
>> I may be wrong, but I didn't get the idea that John's solution will
>> produce an output bitmap file - only an embossed image.
>>
>> I may be wrong again, but as near as I can tell, IVEO doesn't do any
>> image enhancement prior to embossing the image. If I am wrong on these
>> points, John will probably come online and set the record straight.
>>
>> IVEO seems to simply convert the bitmap image to gray scale and emboss
>> the gray scale. While gray scale embossing is okay for some images
>> (especially blank and white images), it is definitely not the best option
>> for many images. After all, if you convert 16 million colors to four levels
>> of gray scale, each level of gray scale represents 4 million different
>> colors. Pixels belonging to each set of 4 million colors will not be
>> distinguishable in the gray scale representation.
>>
>> My objective is to gain access to full-color bitmap images so that I can
>> enhance the image for embossing prior to throwing away all of the color
>> information.
>>
>> Embossed versions of bitmap images are often very difficult to
>> understand, even with a decent description. I believe we need to do
>> everything reasonable to improve the understandability of embossed bitmap
>> images. In some cases, image enhancement techniques at the full-color stage
>> can be used to provide those improvements.
>>
>> So, my quest continues, hopefully without having to pay $445.00 for
>> Acrobat Pro, just to get access to the images.
>>
>> The fallback position, of course, is to use screen shots and an image
>> editor program to crop out the individual images, but that approach is not
>> possible for a blind person to use. You can't crop an image out of a screen
>> shot unless you can see the image.
>>
>> By the way, I don't know how a blind person would carry out the second of
>> the following two steps in John's procedure:
>>
>> * import the PDF into IVEO Creator Pro.
>> * Check the PDF to find which pages have images of interest and emboss
>> those
>> pages.
>>
>> It seems that checking the pdf to find which pages have images would be
>> similar to checking a screen shot of a page to find and crop the image. It
>> seems that you would need to be able to see the pdf on the IVEO screen to
>> know if it contains an image. I am working with pdf files containing
>> anywhere between 30 and 80 pages. Embossing every page in order to identify
>> the pages that contain images would not be practical.
>>
>> Dick Baldwin
>>
>>
>> On Fri, Jan 27, 2012 at 11:48 AM, Richard Baldwin <
>> baldwin at dickbaldwin.com> wrote:
>>
>>> Amanda and others,
>>>
>>> I have contacted Adobe technical support. There solution to the problem
>>> is to purchase Acrobat Pro for $445.00. The tech support rep told me that
>>> their program will extract the pictures intact as separate bitmap files.
>>>
>>> Dick Baldwin
>>>
>>>
>>> On Fri, Jan 27, 2012 at 10:44 AM, Michael Whapples <mwhapples at aim.com>wrote:
>>>
>>>> Hello,
>>>> From what you are describing, my feeling is that the diagrams/images in
>>>> the PDF in question are created from a number of drawing elements rather
>>>> than a single image object. I'm not an expert on PDF, but I think you could
>>>> think of it like the difference of a bitmap being a single element (I think
>>>> PDF has a way to specify the start of a stream object like a bitmap) and an
>>>> SVG being formed from lots of elements like lines and shapes (I think in
>>>> PDF the lines and such like can be created with basic PDF drawing
>>>> facilities so are not in a separate object). When the image is formed from
>>>> lots of elements then it may be hard for the software to know what makes up
>>>> a given diagram in the book/document, it just lays it out as specified and
>>>> you work out what's related. I think one way to tell whether you have this
>>>> sort of image is to see if NVDA will read some of the text labels of the
>>>> image, if it does then its not a pure bitmap (you probably could use the
>>>> read out lout function of adobe reader as well). Therefore I imagine that
>>>> without clever recognition algorithms you are unlikely to get something
>>>> which will extract it as you want.
>>>>
>>>> There is one option I am aware of for a blind person to do this
>>>> independently, IVEO like John suggested, however IVEO isn't a cheap option
>>>> and depending on how much is to be done would determine whether its worth
>>>> the money if providing accessible diagrams from PDF was its only use. IVEO
>>>> does not require a tiger printer, swell paper would work, other embossers
>>>> may (the outputting from IVEO is the question as I think it may only output
>>>> to devices appearing as standard printers). Interesting, the IVEO route
>>>> again is requiring a human to make the decision on what forms the diagram.
>>>>
>>>> Michael Whapples
>>>>
>>>> -----Original Message----- From: Richard Baldwin
>>>> Sent: Friday, January 27, 2012 3:28 PM
>>>> To: Jamal Mazrui
>>>> Cc: Blind Math list for those interested in mathematics
>>>> Subject: Re: [Blindmath] Extracting bitmap images from pdf files
>>>>
>>>>
>>>> Hi Jamal,
>>>>
>>>> It is a great program, easy to use, and probably totally accessible. I
>>>> particularly like the fact that the program doesn't require a windows
>>>> installation. The output data is well organized and including the page
>>>> numbers in the bmp file names is a great help in analyzing them.
>>>>
>>>> Unfortunately, the output produced by the program suffers from the same
>>>> issues that I have encountered with all of the other image extractor
>>>> programs that I have tried. A few of the images come out intact. Most of
>>>> the images don't come out intact.
>>>>
>>>> For example, page three of one of the pdf files that I tested has a
>>>> single
>>>> image of a battery. It is the same image that I enhanced and posted in
>>>> an
>>>> earlier post. Your program produced 54 bmp files for that page. A few of
>>>> them were icons such as arrows exclamation marks, etc. The remaining bmp
>>>> files appear to be a very small pieces of the image of the battery. By
>>>> the
>>>> way, I got the earlier image of the battery by taking a screen shot of
>>>> the
>>>> page and using an image editing program to crop out the battery image.
>>>> None
>>>> of the image extraction programs that I have tested extract the image
>>>> intact.
>>>>
>>>> I don't know anything at all about the internal structure of pdf files,
>>>> and
>>>> this behavior of breaking an image into many small pieces may depend on
>>>> how
>>>> the file is constructed in the first place. In any event, my immediate
>>>> problem has to do with a specific set of pdf files that are the chapters
>>>> from a specific physics book, so this program doesn't solve my problem.
>>>>
>>>> Thanks for offering the program.
>>>> Dick Baldwin
>>>>
>>>> On Fri, Jan 27, 2012 at 5:18 AM, Jamal Mazrui <empower at smart.net>
>>>> wrote:
>>>>
>>>>  In an attempt to facilitate a free, non-web dependent solution, I have
>>>>> written a Windows console-mode utility called PDF2Images, built with
>>>>> PowerBASIC and a PDF library.  The distribution archive, including
>>>>> documentation and source code, is available at
>>>>>
>>>>> http://empowermentzone.com/****pdf2images.zip<http://empowermentzone.com/**pdf2images.zip>
>>>>> <http://**empowermentzone.com/**pdf2images.zip<http://empowermentzone.com/pdf2images.zip>
>>>>> >
>>>>>
>>>>>
>>>>> I am interested in any feedback on how well it works compared to other
>>>>> approaches.
>>>>>
>>>>> Jamal
>>>>>
>>>>>
>>>>>
>>>>>
>>>>
>>>> --
>>>> Richard G. Baldwin (Dick Baldwin)
>>>> Home of Baldwin's on-line Java Tutorials
>>>> http://www.DickBaldwin.com
>>>>
>>>> Professor of Computer Information Technology
>>>> Austin Community College
>>>> (512) 223-4758
>>>> mailto:Baldwin at DickBaldwin.com
>>>> http://www.austincc.edu/**baldwin/ <http://www.austincc.edu/baldwin/>
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>>>>
>>>
>>>
>>>
>>> --
>>> Richard G. Baldwin (Dick Baldwin)
>>> Home of Baldwin's on-line Java Tutorials
>>> http://www.DickBaldwin.com
>>>
>>> Professor of Computer Information Technology
>>> Austin Community College
>>> (512) 223-4758
>>> mailto:Baldwin at DickBaldwin.com
>>> http://www.austincc.edu/baldwin/
>>>
>>
>>
>>
>> --
>> Richard G. Baldwin (Dick Baldwin)
>> Home of Baldwin's on-line Java Tutorials
>> http://www.DickBaldwin.com
>>
>> Professor of Computer Information Technology
>> Austin Community College
>> (512) 223-4758
>> mailto:Baldwin at DickBaldwin.com
>> http://www.austincc.edu/baldwin/
>>
>
>
>
> --
> Richard G. Baldwin (Dick Baldwin)
> Home of Baldwin's on-line Java Tutorials
> http://www.DickBaldwin.com
>
> Professor of Computer Information Technology
> Austin Community College
> (512) 223-4758
> mailto:Baldwin at DickBaldwin.com
> http://www.austincc.edu/baldwin/
>



-- 
Richard G. Baldwin (Dick Baldwin)
Home of Baldwin's on-line Java Tutorials
http://www.DickBaldwin.com

Professor of Computer Information Technology
Austin Community College
(512) 223-4758
mailto:Baldwin at DickBaldwin.com
http://www.austincc.edu/baldwin/

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