[Ipe-discuss] How to resize image to specific length

Nikolaus Rath nrath at trialphaenergy.com
Tue Oct 11 17:02:51 CEST 2016

Hi Otfried,

Thanks, will try that procedure!

For making it more intuitive: can't you just make the scale factor 
proportional to the movement along *one* axis (e.g. the one where most 
of the movement happens)?

It seems to me that if you have the diagonal defined, and want to scale 
along that, than it is trivial to convert this to the corresponding 
movement on one axis. On the other hand, if you have the scaling along 
one axis then it's much harder to obtain the corresponding diagonal...


On 10/08/2016 06:49 AM, Otfried Cheong wrote:
> Yes, this is not as easy it might be - I noticed this several times.
> The problem is that in scale mode, the scaling factor is simply
> determined by the ratio by which you move the cursor (as seen from the
> scaling origin), so, as you say, the corner "drags behind", unless you
> move exactly on the diagonal.
> I'm open for suggestions for how scale mode could be more intuitive.
> Right now, what works is the following:
> With vertex snapping (F4) on, do:
> Translate the top left corner of the image to its target position.
> Then, go to the *target* top right corner and draw a vertical auxiliary
> line downwards from there.
> Go back to the top left corner and set the coordinate system there (F1).
> Go to the bottom right corner of the image and set the direction (F2).
> This will set the main coordinate direction to be the diagonal of the
> image.
>  Turn on boundary snapping (F5).  Use scale mode to drag the bottom
>  right corner of the image to the intersection of the coordinate axis
>  and the auxiliary line (since both boundary and angular snapping are
>  on, the cursor will snap to this intersection point).
> Cheers,
>  Otfried
> On Fri, Oct 7, 2016, at 18:44, Nikolaus Rath wrote:
>> Hello,
>> I would like to re-size an image to a specific length (or height), while
>> keeping the aspect ratio preserved.
>> How do I do that?
>> My naive attempt was to grab the left upper corner of the image (using
>> control point snapping) and move it to the desired location. Then I'd
>> grab the right upper corner with the resize tool, hold shift, and move
>> it horizontally to the desired position (using grid snapping).
>> Unfortunately this does not work. While the cursor snaps to the current
>> position, the corner of the image actually "drags behind", so it ends up
>> larger than it should be.
>> Best,
>> -Nikolaus
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Nikolaus Rath, Ph.D.
Senior Scientist
Tri Alpha Energy, Inc.
+1 949 830 2117 ext 211

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