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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