Relationship between PDF and DPI

[Peter Kronenberg <pe...@torch.ai>]

I'm using PdfRenderer.renderImageToDPI() and I'm trying to understand exactly how the DPI is computed.  From looking at the code, it seems that 72 DPI is the default, meaning that it will have the same resolution as the original document.  Is this correct?
I'm my application, I want to create a thumbnail image, but lower the resolution so that the text is not really readable (even if you zoom in), but one can still see the structure of the page.  So I'm just trying to understand the terminology

Peter Kronenberg  |  Senior AI Analytic ENGINEER
C: 703.887.5623
[Torch AI]<http://www.torch.ai/>
4303 W. 119th St., Leawood, KS 66209
WWW.TORCH.AI<http://www.torch.ai/>

Re: Relationship between PDF and DPI

[Tilman Hausherr <TH...@t-online.de>]

Am 16.12.2021 um 20:07 schrieb Peter Kronenberg:
>
> I’m using PdfRenderer.renderImageToDPI() and I’m trying to understand 
> exactly how the DPI is computed.  From looking at the code, it seems 
> that 72 DPI is the default, meaning that it will have the same 
> resolution as the original document.  Is this correct?
>

72dpi is like scale 1 with the methods that don't have "dpi" in it.

There is no such thing as "resolution as the original document". The 
document could be pure vector graphics. There's only the target.

For thumbnails, a good strategy is to use 72dpi or above, then resize 
the result image so it fits into target width / height.

Tilman


> I’m my application, I want to create a thumbnail image, but lower the 
> resolution so that the text is not really readable (even if you zoom 
> in), but one can still see the structure of the page.  So I’m just 
> trying to understand the terminology
>
> *Peter Kronenberg****| **Senior AI Analytic ENGINEER *
>
> *C: 703.887.5623*
>
> Torch AI <http://www.torch.ai/>
>
> 4303 W. 119th St., Leawood, KS 66209
> WWW.TORCH.AI <http://www.torch.ai/>
>