Hi all,

I want to render an image 720x576 pixels with an horizontal and vertical
resolution of 300 ppp. The format of the image may be bmp or better png.
By "default", the resolution I obtain is 96 ppp.

I read all the documentation and didn't find anything telling me I can
change the resolution of images rendered. Can we modify the resolution ?

Subsidiary question for the experts :
If i decide to render an image of 2106x1728, with 96 ppp resolution
and then use ImageMagick or something else to reduce the size of the image
to 720x576, but with 300ppp
Am I totally crazy ? or is it the only way to obtain what i want ?

Thanks

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breizh_france <nomail@nomail> wrote:
> I want to render an image 720x576 pixels with an horizontal and vertical
> resolution of 300 ppp. The format of the image may be bmp or better png.
> By "default", the resolution I obtain is 96 ppp.

  What's "ppp"?

  What is it that you want anyways? Do you want a 720x576 pixels image,
or do you want a "300 ppp" (whatever that means) image? You are wanting
to different resolutions at the same time? That's obviously impossible.
That's like saying "I want a 640x480-pixel image which is 2000 pixels
wide". That's an oxymoron.

> If i decide to render an image of 2106x1728, with 96 ppp resolution
> and then use ImageMagick or something else to reduce the size of the image
> to 720x576, but with 300ppp
> Am I totally crazy ? or is it the only way to obtain what i want ?

  What is "ppp"?

  The resolution of the image is either 2106x1728 or 720x576. There's nothing
else in those two cases.

-- 
                                                          - Warp

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Warp <war### [at] tagpovrayorg> wrote:
> breizh_france <nomail@nomail> wrote:
> > I want to render an image 720x576 pixels with an horizontal and vertical
> > resolution of 300 ppp. The format of the image may be bmp or better png.
> > By "default", the resolution I obtain is 96 ppp.
>
>   What's "ppp"?
>
>   What is it that you want anyways? Do you want a 720x576 pixels image,
> or do you want a "300 ppp" (whatever that means) image? You are wanting
> to different resolutions at the same time? That's obviously impossible.
> That's like saying "I want a 640x480-pixel image which is 2000 pixels
> wide". That's an oxymoron.
>
> > If i decide to render an image of 2106x1728, with 96 ppp resolution
> > and then use ImageMagick or something else to reduce the size of the image
> > to 720x576, but with 300ppp
> > Am I totally crazy ? or is it the only way to obtain what i want ?
>
>   What is "ppp"?
>
>   The resolution of the image is either 2106x1728 or 720x576. There's nothing
> else in those two cases.
>
> --
>                                                           - Warp

I think he may be referring to dpi/ppi which is really irrelavent in digital
imaging.

Resolution of an image is constant no matter what its 'dpi' is.  Dpi only
effects the way it is displayed on some sort of medium, and this can be
controlled by other means than a setting within an image.  For image
display on a monitor, dpi is defined by the monitor's setting.   In
printing, the dpi can be controlled by the printing software/hardware.

Read here: http://www.rideau-info.com/photos/mythdpi.html

-tgq

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breizh_france nous apporta ses lumieres en ce 2007/07/18 09:58:
> Hi all,
> 
> I want to render an image 720x576 pixels with an horizontal and vertical
> resolution of 300 ppp. The format of the image may be bmp or better png.
> By "default", the resolution I obtain is 96 ppp.
> 
> I read all the documentation and didn't find anything telling me I can
> change the resolution of images rendered. Can we modify the resolution ?
> 
> Subsidiary question for the experts :
> If i decide to render an image of 2106x1728, with 96 ppp resolution
> and then use ImageMagick or something else to reduce the size of the image
> to 720x576, but with 300ppp
> Am I totally crazy ? or is it the only way to obtain what i want ?
> 
> Thanks
> 
> 
> 
The "ppp/ppi" information is any image file is just a number, and a meaningless 
one at that. I say meaningless because it almost NEVER corelate to your actual 
display: My screen is at 120 ppp and images I create where taged 72 ppp under 
Windows 2000, and 96 ppp under XP. SAME image, SAME screen resolution, SAME 
monitor, SAME displayed dimentions, different ppp number.
Pixels Par  Pouce (ppp French), or Pixel Per Inch (ppi English) was an usefull 
information when  printing tramed images, like in newspapers, and changing the 
dimention of the image.

If you want to print at 300 ppp an image that is 720x576 pixels, it will be 
2.4x1.92 inches.

There is a thing called interpolation and dithering, and, to my knowlege, ANY 
printer driver CAN do that. It can take an image of 800x600 pixels and print 
12x9 inches at 1440 ppp. Chose "error diffusion", or something equivalent, 
dithering to prevent any tramé effect.

An image with 720x576 pixel resolution have a dimention dictated by HOW you 
display it, NOT by the number of pixels, and even less by any ppp information.

-- 
Alain
-------------------------------------------------
A day without sunshine is like, night

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Alain wrote:
> The "ppp/ppi" information is any image file is just a number, and a 
> meaningless one at that.

Some layout software uses it to pick the default size for an image when 
you place it on a page. That's about it. I just use PaintShop to 
globally change the "resolution" of a bunch of images I took with my 
camera, or I'd wind up having to manually shrink them all from 10 feet 
wide down to fit on the page.

-- 
   Darren New / San Diego, CA, USA (PST)
     I bet exercise equipment would be a lot more
     expensive if we had evolved from starfish.

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Darren New nous apporta ses lumieres en ce 2007/07/18 21:32:
> Alain wrote:
>> The "ppp/ppi" information is any image file is just a number, and a 
>> meaningless one at that.
> 
> Some layout software uses it to pick the default size for an image when 
> you place it on a page. That's about it. I just use PaintShop to 
> globally change the "resolution" of a bunch of images I took with my 
> camera, or I'd wind up having to manually shrink them all from 10 feet 
> wide down to fit on the page.
> 
That's a bug in the layout software, or at least, a conception miss-asumption.
Today, the asumption you SHOULD make is that any PPI/DPI you find is 
meaningless, and to be ignored.

-- 
Alain
-------------------------------------------------
Where the press is free and every man able to read, all is safe.
Thomas Jefferson

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Thanks for your answers

As it has been said before said, everything is here :

http://www.rideau-info.com/photos/changedpi.html

Regards,

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I _highly_ recommend Irfanview. It is the second best $20 I have ever spent on 
computer software next to V (fileviewer). Irfanview is the easiest and quickest 
image post processing tool I have ever come across in over 30 years of 
operations. I use this tool pretty much every time I turn one of my boxes on.

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Marty Schrader nous apporta ses lumieres en ce 2007/08/18 01:08:
> I _highly_ recommend Irfanview. It is the second best $20 I have ever 
> spent on computer software next to V (fileviewer). Irfanview is the 
> easiest and quickest image post processing tool I have ever come across 
> in over 30 years of operations. I use this tool pretty much every time I 
> turn one of my boxes on.
IrfanView is FREE for presonal, non-comercial, at home use.

-- 
Alain
-------------------------------------------------
Support bacteria. They're the only culture some people have.

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