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Posted to fop-users@xmlgraphics.apache.org by Vincent Hennebert <vh...@gmail.com> on 2009/04/24 12:54:24 UTC
Re: Resolution in vector formats [was: Is it possible to create PDFs
in 96 DPI?]
Hi Martin,
Unless I misunderstood you, this is a different topic. If all the
dimensions in the file are given using absolute units (pt, mm, in,
etc.), then the file is indeed independent of any resolution. It is up
to the output device to convert those measures into the right amount of
pixels, knowing its own resolution. A screen whose resolution is 72dpi
will render a one inch long line on 72 pixels. A screen at 96dpi on 96
pixels. A printer at 600dpi on 600 pixels, etc.
Now, it is true that in the SVG format there is the ‘px’ unit [1] for
which a correspondence must be given. To keep it short, the user has to
define to how many points (or cm, or in) 1 px must be mapped. In FOP
this is done using the ‘source-resolution’ parameter [2]: it tells how
many of those ‘px’ can be found in one inch (72, by default).
If in your SVG file you set the text size to 24pt and your system is
properly set up, then when you display the file on the screen at a zoom
of 100% you will actually see that the text is 24pt high.
[1] http://www.w3.org/TR/SVG11/coords.html#Units
[2] http://xmlgraphics.apache.org/fop/0.95/configuration.html
Vincent
Martin Jacobson wrote:
> Hi,
>
> <rant>
> There seems to be a misconception frequently found in the SVG/PDF
> community that because vector graphics can be scaled with no change in
> image quality, they are somehow 'independent' of notions of resolution.
> Unfortunately, this isn't correct. Any piece of vector image must be
> drawn at the same scale as all the others in order to have the correct
> relative size in the final image. So we have to know what that scale is.
> It would be nice to be able to set that scale so it matched the
> resolution of the output device because then we could place text at a
> given (absolute) size, such as 24pt knowing that changing the scale
> would not change the relative size of the text, but alas! this is not
> the case; someone decided that The Scale shall be 1:72, which means that
> text has to be manually scaled according to the output resolution.
> </rant>
>
> I feel better for that
> Martin
>
>
> On 24 Apr 2009, at 10:32, Vincent Hennebert wrote:
>
>> Hi,
>>
>> Like you noticed the resolution only applies to images. I am slightly
>> puzzled by the way you compare both outputs: are you putting the sheet
>> of paper next to the screen and looking for differences?
>>
>> Then note that the HTML result is likely to be highly different from one
>> environment to the other (think of a desktop machine compared to
>> a smartphone), and it is dependent on many settings: the resolution of
>> the screen, the default font and font sizes chosen by the user, the
>> default stylesheet they may want to apply, etc.
>>
>> Also, PDF is a vectorial format, so the notion of resolution doesn’t
>> apply to it (except the raster images that it may contain).
>>
>> So yes, in the end what you want to do is to play with font sizes,
>> rather on the FO output. For the HTML output better leave them to their
>> default values, and let the users choose the default sizes that suit
>> them.
>>
>> kkapelon freemail gr wrote:
>>> Hello list!
>>>
>>> I have an XML file which is either converted to PDF (via FOP) or to
>>> XHTML (via another XSL stylesheet)
>>>
>>> I have noticed however that things look different in (printed) PDF
>>> and (on-screen) HTML formats.
>>> The sizes are different for the text elements.
>>>
>>> After searching for a cause it came to my attention that PDF files
>>> from FOP
>>> are rendered at 72DPI (correct me if I am wrong) while the
>>> browser/screen/OS works at 96DPI.
>>>
>>> I found the configuration for dpi at
>>> http://xmlgraphics.apache.org/fop/0.95/configuration.html, but this
>>> applies only to images and not text.
>>>
>>> So is there a workaround to make things appear on print the same as
>>> they are on screen?
>>>
>>> I am thinking of manully changing the sizes in one stylesheet (either
>>> for FO or HTML) to bring it
>>> to the same "size" with the other. But I wonder if there is a more
>>> elegant solution.
>>>
>>> Thank you
>>
>>
>> Hope this clarifies the thing a bit.
>> Vincent
>>
>> ---------------------------------------------------------------------
>> To unsubscribe, e-mail: fop-users-unsubscribe@xmlgraphics.apache.org
>> For additional commands, e-mail: fop-users-help@xmlgraphics.apache.org
>>
>
> Sent from my Mac
>
>
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Re: Resolution in vector formats [was: Is it possible to create PDFs in 96 DPI?]
Posted by Martin Jacobson <ja...@gmail.com>.
Hi Vincent,
Having got my <rant /> off my chest, I won't argue with you - it is,
as you say, a little off-topic. My gripe is with the definition, not
the implementation!
best wishes,
Martin
On 24 Apr 2009, at 11:54, Vincent Hennebert wrote:
> Hi Martin,
>
> Unless I misunderstood you, this is a different topic. If all the
> dimensions in the file are given using absolute units (pt, mm, in,
> etc.), then the file is indeed independent of any resolution. It is up
> to the output device to convert those measures into the right amount
> of
> pixels, knowing its own resolution. A screen whose resolution is 72dpi
> will render a one inch long line on 72 pixels. A screen at 96dpi on 96
> pixels. A printer at 600dpi on 600 pixels, etc.
>
> Now, it is true that in the SVG format there is the ‘px’ unit [1] for
> which a correspondence must be given. To keep it short, the user has
> to
> define to how many points (or cm, or in) 1 px must be mapped. In FOP
> this is done using the ‘source-resolution’ parameter [2]: it tells how
> many of those ‘px’ can be found in one inch (72, by default).
>
> If in your SVG file you set the text size to 24pt and your system is
> properly set up, then when you display the file on the screen at a
> zoom
> of 100% you will actually see that the text is 24pt high.
>
> [1] http://www.w3.org/TR/SVG11/coords.html#Units
> [2] http://xmlgraphics.apache.org/fop/0.95/configuration.html
>
>
> Vincent
>
>
> Martin Jacobson wrote:
>> Hi,
>>
>> <rant>
>> There seems to be a misconception frequently found in the SVG/PDF
>> community that because vector graphics can be scaled with no change
>> in
>> image quality, they are somehow 'independent' of notions of
>> resolution.
>> Unfortunately, this isn't correct. Any piece of vector image must be
>> drawn at the same scale as all the others in order to have the
>> correct
>> relative size in the final image. So we have to know what that
>> scale is.
>> It would be nice to be able to set that scale so it matched the
>> resolution of the output device because then we could place text at a
>> given (absolute) size, such as 24pt knowing that changing the scale
>> would not change the relative size of the text, but alas! this is not
>> the case; someone decided that The Scale shall be 1:72, which means
>> that
>> text has to be manually scaled according to the output resolution.
>> </rant>
>>
>> I feel better for that
>> Martin
>>
>>
>> On 24 Apr 2009, at 10:32, Vincent Hennebert wrote:
>>
>>> Hi,
>>>
>>> Like you noticed the resolution only applies to images. I am
>>> slightly
>>> puzzled by the way you compare both outputs: are you putting the
>>> sheet
>>> of paper next to the screen and looking for differences?
>>>
>>> Then note that the HTML result is likely to be highly different
>>> from one
>>> environment to the other (think of a desktop machine compared to
>>> a smartphone), and it is dependent on many settings: the
>>> resolution of
>>> the screen, the default font and font sizes chosen by the user, the
>>> default stylesheet they may want to apply, etc.
>>>
>>> Also, PDF is a vectorial format, so the notion of resolution doesn’t
>>> apply to it (except the raster images that it may contain).
>>>
>>> So yes, in the end what you want to do is to play with font sizes,
>>> rather on the FO output. For the HTML output better leave them to
>>> their
>>> default values, and let the users choose the default sizes that suit
>>> them.
>>>
>>> kkapelon freemail gr wrote:
>>>> Hello list!
>>>>
>>>> I have an XML file which is either converted to PDF (via FOP) or to
>>>> XHTML (via another XSL stylesheet)
>>>>
>>>> I have noticed however that things look different in (printed) PDF
>>>> and (on-screen) HTML formats.
>>>> The sizes are different for the text elements.
>>>>
>>>> After searching for a cause it came to my attention that PDF files
>>>> from FOP
>>>> are rendered at 72DPI (correct me if I am wrong) while the
>>>> browser/screen/OS works at 96DPI.
>>>>
>>>> I found the configuration for dpi at
>>>> http://xmlgraphics.apache.org/fop/0.95/configuration.html, but this
>>>> applies only to images and not text.
>>>>
>>>> So is there a workaround to make things appear on print the same as
>>>> they are on screen?
>>>>
>>>> I am thinking of manully changing the sizes in one stylesheet
>>>> (either
>>>> for FO or HTML) to bring it
>>>> to the same "size" with the other. But I wonder if there is a more
>>>> elegant solution.
>>>>
>>>> Thank you
>>>
>>>
>>> Hope this clarifies the thing a bit.
>>> Vincent
>>>
>>> ---------------------------------------------------------------------
>>> To unsubscribe, e-mail: fop-users-unsubscribe@xmlgraphics.apache.org
>>> For additional commands, e-mail: fop-users-help@xmlgraphics.apache.org
>>>
>>
>> Sent from my Mac
>>
>>
>> ---------------------------------------------------------------------
>> To unsubscribe, e-mail: fop-users-unsubscribe@xmlgraphics.apache.org
>> For additional commands, e-mail: fop-users-
>> help@xmlgraphics.apache.org
>>
>
> ---------------------------------------------------------------------
> To unsubscribe, e-mail: fop-users-unsubscribe@xmlgraphics.apache.org
> For additional commands, e-mail: fop-users-help@xmlgraphics.apache.org
>
Sent from my Mac
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