Rectpack is a collection of heuristic algorithms for solving the 2D knapsack problem, also known as the bin packing problem. In essence packing a set of rectangles into the smallest number of bins.
Download the package or clone the repository, and then install with:
python setup.py installor use pypi:
pip install rectpackPacking rectangles into a number of bins is very simple:
from rectpack import newPacker
rectangles = [(100, 30), (40, 60), (30, 30),(70, 70), (100, 50), (30, 30)]
bins = [(300, 450), (80, 40), (200, 150)]
packer = newPacker()
# Add the rectangles to packing queue
for r in rectangles:
packer.add_rect(*r)
# Add the bins where the rectangles will be placed
for b in bins:
packer.add_bin(*b)
# Start packing
packer.pack()Once the rectangles have been packed the results can be accessed individually
# Obtain number of bins used for packing
nbins = len(packer)
# Index first bin
abin = packer[0]
# Bin dimmensions (bins can be reordered during packing)
width, height = abin.width, abin.height
# Number of rectangles packed into first bin
nrect = len(packer[0])
# Second bin first rectangle
rect = packer[1][0]
# rect is a Rectangle object
x = rect.x # rectangle bottom-left x coordinate
y = rect.y # rectangle bottom-left y coordinate
w = rect.width
h = rect.heightlooping over all of them
for abin in packer:
print(abin.bid) # Bin id if it has one
for rect in abin:
print(rect)or using rect_list()
# Full rectangle list
all_rects = packer.rect_list()
for rect in all_rects:
b, x, y, w, h, rid = rect
# b - Bin index
# x - Rectangle bottom-left corner x coordinate
# y - Rectangle bottom-left corner y coordinate
# w - Rectangle width
# h - Rectangle height
# rid - User asigned rectangle id or NoneLastly all the dimmension (bins and rectangles) must be integers or decimals to avoid collisions caused by floating point rounding. If your data is floating point use float2dec to convert float values to decimals (see float below)
A more detailed description of API calls:
class newPacker([, mode][, bin_algo][, pack_algo][, sort_algo][, rotation])
Return a new packer object
packer.add_bin(width, height[, count][, bid])
Add empty bin or bins to a packer
packer.add_rect(width, height[, rid])
Add rectangle to packing queue
packer.pack():
Starts packing process (only for offline mode).
packer.rect_list():
Returns the list of packed rectangles, each one represented by the tuple (b, x, y, w, h, rid) where:
This library implements three of the algorithms described in [1] Skyline, Maxrects, and Guillotine, with the following variants:
MaxRects
Skyline
Guillotine
I recommend to use the default algorithm unless the packing is too slow, in that case switch to one of the Guillotine variants for example GuillotineBssfSas. You can learn more about the algorithms in [1].
Rectpack is thoroughly tested, run the tests with:
python setup.py testor
python -m unittest discoverIf you need to use floats just convert them to fixed-point using a Decimal type, be carefull rounding up so the actual rectangle size is always smaller than the conversion. Rectpack provides helper funcion float2dec for this task, it accepts a number and the number of decimals to round to, and returns the rounded Decimal.
from rectpack import float2dec, newPacker
float_rects = [...]
dec_rects = [(float2dec(r[0], 3), float2dec(r[1], 3)) for r in float_rects]
p = newPacker()
...[1] Jukka Jylang - A Thousand Ways to Pack the Bin - A Practical Approach to Two-Dimensional Rectangle Bin Packing (2010)
[2] Huang, E. Korf - Optimal Rectangle Packing: An Absolute Placement Approach (2013)