Re: Use MetaPost to distort images?

[Henning Hraban Ramm via ntg-context <ntg-context@ntg.nl>]

> Am 03.09.2021 um 18:24 schrieb Hans Hagen via ntg-context <ntg-context@ntg.nl>:
> 
> On 9/3/2021 12:28 PM, Henning Hraban Ramm via ntg-context wrote:
>> Hi, is it possible to apply geometric transformations to images using MetaPost?
>> This is again way over my head, but I’m still trying different methods to let a ConTeXt document look more “hand-made”.
>> In my example*, I added frame and shadow to a photo and _distorted_ it slightly to have it look like a postcard was glued on the page (with a piece of tape). I’d like to automate and randomize that process.
>> I guess I could achieve something similar with ImageMagick (not with GraphicsMagick), but if it would be possible inside LMTX that would be great.
> the question is not so much if it can be done but how far we should go in doing things .. so, only as friday afternoon distraction, and because
> i wanted to upload anyway (not done yet) i'll meta-imp-magick that uses the gm lib interface (that only does simple conversions, but i added bur and noise an dcan add some more if needed as long as there is no weird stuff or code bloat)
> 
> not in the core, just as 'imp' because we don't want library dependencies (and the optional libs are lightweight delayed loading ones)
> 
> now, the drawback of course is that one needs gm installed (quite large) but it does work on my windows box so ...

Thank you!

That’s interesting and I can probably use it for a different project, but for what I had in mind, GM wasn’t enough. IM has much more features (and probably also flaws), is even bigger, with more dependencies, but I could install both with MacPorts.

I guess it’s on me to write a wiki page about GM.
And maybe adapt your code to IM...

I just thought since MP is great for geometrical calculations it might also be able to use transformation matrices on images.
But since I don’t understand matrix calculations anyway, I’ll live without.

Generally, I’d like to delay image manipulation as long as possible – only ConTeXt knows the final size of the used images, and since I want to keep e.g. frames and shadows at the same size for all images I need to calculate with that final size. 


Hraban
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