#10 Inverse Function Question

[Anonymous]

Hi Timo,

we use JavaScript Clipper for our painting app PaintSupreme which is right now in early alpha at www.paintsupreme.com.

The whole selection tool is based on Clipper. Now a question.

If I have a project like 640x480 with a selection path which is inside that space but can also be partially outside the canvas, how would I compute the inverse path of the selection path relative to the 640x480 canvas ?

Thanks for any help and thanks alot for JavaScript Clipper. It helps us a lot with PaintSupreme.

Markus

[Timo Kähkönen]

Hi, Markus!

Hard to say without any example image. Could you make an image about the situation?

[Ernesto Civello]

Hi Markus, accordin to me you can reverse your path (via ReversePath
command) and call AddPath with the path of your canvas.

So, if your path is A and your rectangle (640,480) is B, you have to compute

addPath(reverse(A),B)

Bye bye.

Il giorno mar 7 giu 2016 alle ore 15:21 Timo timo23414@users.sf.net ha
scritto:

Hi, Markus!

Hard to say without any example image. Could you make an image about the
situation?

---

• [tickets:#10] https://sourceforge.net/p/jsclipper/tickets/10/ Inverse
  Function Question*

Status: open
Milestone: 1.0
Created: Tue Jun 07, 2016 08:50 AM UTC by Anonymous
Last Updated: Tue Jun 07, 2016 08:50 AM UTC
Owner: nobody

Hi Timo,

we use JavaScript Clipper for our painting app PaintSupreme which is right
now in early alpha at www.paintsupreme.com.

The whole selection tool is based on Clipper. Now a question.

If I have a project like 640x480 with a selection path which is inside
that space but can also be partially outside the canvas, how would I
compute the inverse path of the selection path relative to the 640x480
canvas ?

Thanks for any help and thanks alot for JavaScript Clipper. It helps us a
lot with PaintSupreme.

Markus

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[Markus Moenig]

Hi Timo,

attached is an image of a selection in the canvas. The inverse would be that everything INSIDE the canvas would be in the opposite state.

Ernesto, thanks for the tip, will try it out!

Best,

Markus

[Timo Kähkönen]

It is the DIFFERENCE operation so that the SUBJECT is the canvas path (eg 640x480) and the CLIP is the selection path (or UNION of selection paths).

You can experiment these in:
http://jsclipper.sourceforge.net/6.1.3.2/main_demo.html

SUBJECT: M415,283.89 L85,283.89 L85,66.09 L415,66.09Z

CLIP: M74.5,115.5 L111,111 L108,7 L385,6 L380,83 L480,95 L479,156 L191,143 L184,341 L127,339 L118,148 L12,146 L11.5,113.5Z

You can add these paths pressing Polygons - Custom and pasting those into Subj and Clip fields and press Save as New. Then press DIFFERENCE in the Clip type (operation) -field.

[Timo Kähkönen]

Or if you need also those outside-areas, use XOR.

[Markus Moenig]

Thanks a lot for your (fast) help! Yes, the difference operator works just great for this. Great support!