fitting a picture to the available space

* fitting a picture to the available space
@ 2008-09-10 22:06 Thomas A. Schmitz
  2008-09-11  7:28 ` Hans Hagen
  2008-09-11 16:31 ` Mojca Miklavec
  0 siblings, 2 replies; 18+ messages in thread
From: Thomas A. Schmitz @ 2008-09-10 22:06 UTC (permalink / raw)
  To: mailing ConTeXt users list for

Hi guys,

I'm pulling my hair out. I'm trying to set up an automatism to fit  
pictures to the available space on a slide. I need to consider three  
parameters:

1. If the user supplies a value for width= or height= , use this value  
(captured in a macro);

2. respect the maxwidth and maxheight which must not exceed the frame;

3. if the picture is smaller than the available space, blow it up so  
that it reaches the maxwidth or maxheight (but doesn't exceed either).

factor=max or =fit does not work because it allows pictures to exceed  
one of the maximum values. About a year ago Giuseppe Bilotta wrote a  
message which I append; it describes my problem. Is there a generic  
solution for this problem? If there is, I'll gladly take it; if there  
isn't, I thought I had a solution but may need help with expanding and  
conditionals, then I'll be back with more questions.

Anyway, good night all, and thanks.

Thomas

> Subject: Re: [NTG-context] factor=fit images don't fit
> Sunday, July 22, 2007 Hans Hagen wrote:
>
> > the fit assumes operating on a page not in a box;
>
> Ah, didn't know that. I couldn't even tell from the sources,
> since it uses enclosing box dimensions and not page or paper
> sizes. I suspect the logic is broken at the page level too
> though, let me explain why.
>
> Currently, if I understand the code correctly, factor=fit
> expands the figure to have its major direction fit, while
> factor=max expands the figure to have its minor direction
> fit.
>
> Instead, the behavior I would expect from fit (resp. max) is
> for the *expansion ratio* to be the minimum (resp. maximum)
> of the expansion ratios in the two directions (not the sizes
> in those directions, but the ratio between the sizes of the
> figure and the container). The difference is noticeable when
> the container and contained have different aspect ratios.
>
> Consider for example a 20x30mm figure in a 50x150mm page
> (strange numbers, just used to show what I mean): with the
> current code, using 'fit' would consider the largest
> dimension (30) and thus calculate a factor of 150/30 = 5,
> but this gives us an image which is 100x150mm, i.e. an image
> that doesn't fit! Whereas, if we computed the ratios 50/20 =
> 2.5 and 150/30 = 5, we would know that the ratio to be
> picked was 2.5 in 'fit' and 5 in 'max'.
>
> Or I misintepreting the meaning of 'fit' and 'max'?
>
> > an alternative is:
>
> > \framed[width=5cm,height4cm]
> >
> > {\externalfigure[mill.png][maxwidth=4cm,maxheight=5cm,width=10cm]}
>
> > i.e. setting the maximum values
>
> I hadn't thought about using width and maxwidth (and
> maxheight) at the same time, thanks. Of course, I'd rather
> have 'fit' and 'max' usable in boxes :)
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