Point Inside a Polygon //JavaScript Function

jonasraoni (Jonas Raoni Soares Silva) — Sun, 30 Mar 2008 16:57:56 GMT

Checks whether a point is inside a polygon.
Adapted from: [http://www.ecse.rpi.edu/Homepages/wrf/Research/Short_Notes/pnpoly.html]

[UPDATED CODE AND HELP CAN BE FOUND HERE: Point Inside a Polygon]



//+ Jonas Raoni Soares Silva

//@ http://jsfromhell.com/classes/is-point-in-poly [v1.0]



function isPointInPoly(poly, pt){

	for(var c = false, i = -1, l = poly.length, j = l - 1; ++i < l; j = i)

		((poly[i].y <= pt.y && pt.y < poly[j].y) || (poly[j].y <= pt.y && pt.y < poly[i].y))

		&& (pt.x < (poly[j].x - poly[i].x) * (pt.y - poly[i].y) / (poly[j].y - poly[i].y) + poly[i].x)

		&& (c = !c);

	return c;

}

Example

Drawing an arrow cursor

korakot (Korakot Chaovavanich) — Fri, 10 Feb 2006 09:06:11 GMT

Calling polygon may be faster than a blit.



x,y = 20,20

arrow = [(0,0), (0,10), (2,8), (4,12), (6,11), (4,7), (7,7)]

canvas.polygon([(x+dx,y+dy) for dx,dy in arrow], 0, 0xffffff)

Here's an example app. It let you move cursor around.
When you press the select key, a red circle is drawn.
The longer you press, the bigger the circle.

Start with the usual stuff



import e32

from appuifw import *

from key_codes import *



class Keyboard(object):

    def __init__(self):

        self.state = {}  # is this key pressing ?

        self.buffer= {}  # is it waiting to be processed ?

    def handle_event(self, event): # for event_callback

        code = event['scancode']

        if event['type'] == EEventKeyDown:

            self.buffer[code]= 1   # put into queue

            self.state[code] = 1

        elif event['type'] == EEventKeyUp:

            self.state[code] = 0

    def pressing(self, code):      # just check

        return self.state.get(code,0)

    def pressed(self, code):       # check and process the event

        if self.buffer.get(code,0):

            self.buffer[code] = 0  # take out of queue

            return 1

        return 0



key = Keyboard()

app.body = canvas = Canvas(event_callback=key.handle_event)



def quit():

    global running

    running = 0



app.exit_key_handler = quit

running = 1

Then the main part of this specific app.



x,y = 20,20

arrow = [(0,0), (0,10), (2,8), (4,12), (6,11), (4,7), (7,7)]



while running:

    if key.pressing(EScancodeUpArrow):

        y -= 1

    if key.pressing(EScancodeDownArrow):

        y += 1

    if key.pressing(EScancodeLeftArrow):

        x -= 1

    if key.pressing(EScancodeRightArrow):

        x += 1

    if key.pressed(EScancodeSelect):

        r = 1

        while key.pressing(EScancodeSelect):

            r += 1       # bigger red circle

            canvas.ellipse([(x-r,y-r),(x+r,y+r)], fill=0xff0000)

            canvas.polygon([(x+dx,y+dy) for dx,dy in arrow], 0, 0xffffff)

            e32.ao_sleep(0.03)



    canvas.clear()

    canvas.polygon([(x+dx,y+dy) for dx,dy in arrow], 0, 0xffffff)

    e32.ao_sleep(0.01)

DZone Snippets: polygon code

Point Inside a Polygon //JavaScript Function

Drawing an arrow cursor