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box2d

2D Graphics
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box2d

rectangle math


local box = require'box2d'

Math for 2D rectangles defined as (x, y, w, h) where w > 0 and h > 0.

API

representation forms
box.corners(x, y, w, h) -> x1, y1, x2, y2 left,top and right,bottom corners
box.rect(x1, y1, x2, y2) -> x, y, w, h box given left,top and right,bottom corners
normalization
box.normalize(x, y, w, h) -> x, y, w, h return the same box with positive width and height
layouting
box.align(w, h, halign, valign,
bx, by, bw, bh) -> x, y, w, h
align a box in another box
box.vsplit(i, sh, x, y, w, h) -> x, y, w, h slice a box horizontally at a certain height and return the i'th box. if sh is negative, slicing is done from the bottom side.
box.hsplit(i, sw, x, y, w, h) -> x, y, w, h slice a box vertically at a certain width and return the i'th box. if sw is negative, slicing is done from the right side.
box.nsplit(i, n, direction, x, y, w, h) -> x, y, w, h slice a box in n equal slices, vertically or horizontally, and return the i'th box. direction = 'v' or 'h'
box.translate(x0, y0, x, y, w, h) -> x, y, w, h move a box
box.offset(d, x, y, w, h) -> x, y, w, h offset a box by d, outward if d is positive
box.fit(w, h, bw, bh) -> w, h fit a box into another box preserving aspect ratio. use align() to position the box
hit testing
box.hit(x0, y0, x, y, w, h) -> true | false check if a point (x0, y0) is inside rect (x, y, w, h)
box.hit_edges(x0, y0, d, x, y, w, h)
-> hit, left, top, right, bottom
hit test for edges and corners
edge snapping
box.snap_edges(d, x, y, w, h, rectangles[, opaque])
-> x, y, w, h
snap the sides of a rectangle against a list of rectangles of form {{x=,y=,w=,h=},...}. if opaque = true, the rectangles are considered opaque, in which case they must be sorted front-to-back.
box.snap_pos(d, x, y, w, h, rectangles[, opaque])
-> x, y, w, h
snap the position of a rectangle against a list of rectangles.
box.snapped_edges(d, x1, y1, w1, h1, x2, y2, w2, h2[, opaque])
-> snapped, left, top, right, bottom
check if two boxes are snapped and on which edges.
overlapping test
box.overlapping(x1, y1, w1, h1, x2, y2, w2, h2) -> true | false check if two boxes overlap.
clipping
box.clip(x, y, w, h, x0, y0, w0, h0) -> x1, y1, w1, h1 intersect two normalized boxes

OOP API

Operations never mutate the object, instead they return a new one.

box(x, y, w, h) -> box create a new box object
box.x, box.y, box.w, box.h box coordinates (for reading and writing)
box:rect() -> x, y, w, h
box() -> x, y, w, h
coordinates unpacked
box:corners() -> x1, y1, x2, y2 left,top and right,bottom corners
box:align(halign, valign, parent_box) -> box align
box:vsplit(i, sh) -> box split vertically
box:hsplit(i, sw) -> box split horizontally
box:nsplit(i, n, direction) -> box split in equal parts
box:translate(x0, y0) -> box translate
box:offset(d) -> box offset by d (outward if d is positive)
box:fit(parent_box, halign, valign) -> box enlarge/shrink-to-fit and align
box:hit(x0, y0) -> true | false hit test
box:hit_edges(x0, y0, d) -> hit, left, top, right, bottom hit test for edges
box:snap_edges(d, boxes) -> box snap the edges to a list of boxes
box:snap_pos(d, boxes) -> box snap the position
box:overlapping(box) -> true | false overlapping test
box:clip(box) -> box clip box to fit inside another box

Last updated: 23 months ago | Edit on GitHub

Pkg type:Lua
Version: r2-8-g6a49a98
Last commit:
License: PD
Requires: none
Required by: bitmap  cplayer  nw  bmp  videoinput 

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