On Wednesday 26 March 2003 06:35 pm, Daniel Carrera wrote:
> Hello,
> I've been using Gimp for a while.  I keep hearing that Gimp has a 72dpi
> limitation and Photoshop doesn't, but I really don't understand how that
> is.  I am interested in trying out some printed postes, and I want to
> understand this issue beforehand.
Gimp defaults to 72 pixels. But when you create a new item, or import a 
PostScritp file etc. you have the option of setting the dpi.
> This is how I understand the situation, perhaps someone can explain to me
> where I'm wrong:
> 1) Gimp understands images as a matrix of pixels.  There is no concept of
> physical units like 'inches'.
On most screens you have an op[tion of inches or pixels.
> 2) If I have an image that is 600x600 pixels, and I print it out so it
> comes out at 1x1 inches, I have printed a 600dpi image.
Correct AFAIK. I fyou brought this image into Gimp it ould automatically scale 
it at e.g., 25% so I wouldn't overflow the screen. But it would still be a 
600 dpi image internally.
> 3) The jpeg, gif and png formats are matrices of pixels.  They don't have
> a notion of 'inches'.
Gimp does. I resize images to a specific size all the time. 
Remember that Gimp is not handling your image in an external format. It is 
handling it in its own format. 
> 4) The eps format does have a notion of index.
> Given facts (1)-(4), I can produce a 10x15in poster at 600dpi this way:
> - Start with a jpeg/png that is 6000x9000 pixels.
> - Do some gimping.
> - Export to eps and set width and height to 10x15in.
> - Print the eps file.
You may find that a file that is as you describe is huge and unwieldy. But I 
think it could be done. 
> I don't see where the 72dpi limitation is.  It seems that Gimp has no
> knowlege of dpi except when it exports to eps.
No, it also has knowledge of dpi when you create a new image. And it appears 
to maintain the dpi when it imports an image. 

> Where exactly is Gimp's limitation?
Gimp is more oriented to online images than to printed images. But the only 
serious limitation it has AFAIK is that it does not work in CMYK internally.
So for color printing you have a couple of choices:
1. Produce an RPG file and convert it to CMYK using an external program.
2. Use Gimp to create CMYK separations. 

DISCLAIMER. I am a (perpetual) newbie and some of the above may be incorrect.

John Culleotn
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