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createPNG.py
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createPNG.py
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#!/usr/bin/env python
"""Simple PNG Canvas for Python - updated for bytearray()"""
__version__ = "1.0.1"
__author__ = "Rui Carmo (http://the.taoofmac.com)"
__copyright__ = "CC Attribution-NonCommercial-NoDerivs 2.0 Rui Carmo"
__contributors__ = ["http://collaboa.weed.rbse.com/repository/file/branches/pgsql/lib/spark_pr.rb"], ["Eli Bendersky"]
import os, sys, zlib, struct
signature = struct.pack("8B", 137, 80, 78, 71, 13, 10, 26, 10)
# alpha blends two colors, using the alpha given by c2
def blend(c1, c2):
return [c1[i]*(0xFF-c2[3]) + c2[i]*c2[3] >> 8 for i in range(3)]
# compute a new alpha given a 0-0xFF intensity
def intensity(c,i):
return [c[0],c[1],c[2],(c[3]*i) >> 8]
# compute perceptive grayscale value
def grayscale(c):
return int(c[0]*0.3 + c[1]*0.59 + c[2]*0.11)
# compute gradient colors
def gradientList(start,end,steps):
delta = [end[i] - start[i] for i in range(4)]
grad = []
for i in range(steps+1):
grad.append([start[j] + (delta[j]*i)/steps for j in range(4)])
return grad
class PNGCanvas:
def __init__(self, width, height, bgcolor=bytearray([0xff,0xff,0xff,0xff]),color=bytearray([0,0,0,0xff])):
self.width = width
self.height = height
self.color = color #rgba
self.bgcolor = bgcolor
self.canvas = bytearray(self.bgcolor * 4 * width * height)
def _offset(self, x, y):
return y * self.width * 4 + x * 4
def point(self,x,y,color=None):
if x<0 or y<0 or x>self.width-1 or y>self.height-1: return
if color == None:
color = self.color
o = self._offset(x,y)
self.canvas[o:o+3] = blend(self.canvas[o:o+3],bytearray(color))
def _rectHelper(self,x0,y0,x1,y1):
x0, y0, x1, y1 = int(x0), int(y0), int(x1), int(y1)
if x0 > x1: x0, x1 = x1, x0
if y0 > y1: y0, y1 = y1, y0
return [x0,y0,x1,y1]
def verticalGradient(self,x0,y0,x1,y1,start,end):
x0, y0, x1, y1 = self._rectHelper(x0,y0,x1,y1)
grad = gradientList(start,end,y1-y0)
for x in range(x0, x1+1):
for y in range(y0, y1+1):
self.point(x,y,grad[y-y0])
def rectangle(self,x0,y0,x1,y1):
x0, y0, x1, y1 = self._rectHelper(x0,y0,x1,y1)
self.polyline([[x0,y0],[x1,y0],[x1,y1],[x0,y1],[x0,y0]])
def filledRectangle(self,x0,y0,x1,y1):
x0, y0, x1, y1 = self._rectHelper(x0,y0,x1,y1)
for x in range(x0, x1+1):
for y in range(y0, y1+1):
self.point(x,y,self.color)
def copyRect(self,x0,y0,x1,y1,dx,dy,destination):
x0, y0, x1, y1 = self._rectHelper(x0,y0,x1,y1)
for x in range(x0, x1+1):
for y in range(y0, y1+1):
d = destination._offset(dx+x-x0,dy+y-y0)
o = self._offset(x,y)
destination.canvas[d:d+4] = self.canvas[o:o+4]
def blendRect(self,x0,y0,x1,y1,dx,dy,destination,alpha=0xff):
x0, y0, x1, y1 = self._rectHelper(x0,y0,x1,y1)
for x in range(x0, x1+1):
for y in range(y0, y1+1):
o = self._offset(x,y)
rgba = self.canvas[o:o+4]
rgba[3] = alpha
destination.point(dx+x-x0,dy+y-y0,rgba)
# draw a line using Xiaolin Wu's antialiasing technique
def line(self,x0, y0, x1, y1):
# clean params
x0, y0, x1, y1 = int(x0), int(y0), int(x1), int(y1)
if y0>y1:
y0, y1, x0, x1 = y1, y0, x1, x0
dx = x1-x0
if dx < 0:
sx = -1
else:
sx = 1
dx *= sx
dy = y1-y0
# 'easy' cases
if dy == 0:
for x in range(x0,x1,sx):
self.point(x, y0)
return
if dx == 0:
for y in range(y0,y1):
self.point(x0, y)
self.point(x1, y1)
return
if dx == dy:
for x in range(x0,x1,sx):
self.point(x, y0)
y0 = y0 + 1
return
# main loop
self.point(x0, y0)
e_acc = 0
if dy > dx: # vertical displacement
e = (dx << 16) / dy
for i in range(y0,y1-1):
e_acc_temp, e_acc = e_acc, (e_acc + e) & 0xFFFF
if (e_acc <= e_acc_temp):
x0 = x0 + sx
w = 0xFF-(e_acc >> 8)
self.point(x0, y0, intensity(self.color,(w)))
y0 = y0 + 1
self.point(x0 + sx, y0, intensity(self.color,(0xFF-w)))
self.point(x1, y1)
return
# horizontal displacement
e = (dy << 16) / dx
for i in range(x0,x1-sx,sx):
e_acc_temp, e_acc = e_acc, (e_acc + e) & 0xFFFF
if (e_acc <= e_acc_temp):
y0 = y0 + 1
w = 0xFF-(e_acc >> 8)
self.point(x0, y0, intensity(self.color,(w)))
x0 = x0 + sx
self.point(x0, y0 + 1, intensity(self.color,(0xFF-w)))
self.point(x1, y1)
def polyline(self,arr):
for i in range(0,len(arr)-1):
self.line(arr[i][0],arr[i][1],arr[i+1][0], arr[i+1][1])
def dump(self):
scanlines = bytearray()
for y in range(self.height):
scanlines.append('\0') # filter type 0 (None)
#print y * self.width * 4, (y+1) * self.width * 4
#print self.canvas[y * self.width * 4:(y+1) * self.width * 4]
scanlines.extend(self.canvas[(y * self.width * 4):((y+1) * self.width * 4)])
# image represented as RGBA tuples, no interlacing
return signature + \
self.pack_chunk('IHDR', struct.pack("!2I5B",self.width,self.height,8,6,0,0,0)) + \
self.pack_chunk('IDAT', zlib.compress(str(scanlines),9)) + \
self.pack_chunk('IEND', '')
def pack_chunk(self,tag,data):
to_check = tag + data
return struct.pack("!I",len(data)) + to_check + struct.pack("!I", zlib.crc32(to_check) & 0xFFFFFFFF)
def load(self,f):
assert f.read(8) == signature
for tag, data in self.chunks(f):
if tag == "IHDR":
( width,
height,
bitdepth,
colortype,
compression, filter, interlace ) = struct.unpack("!2I5B",data)
self.width = width
self.height = height
self.canvas = bytearray(self.bgcolor * 4 * width * height)
if (bitdepth,colortype,compression, filter, interlace) != (8,6,0,0,0):
raise TypeError('Unsupported PNG format')
# we ignore tRNS for the moment
elif tag == 'IDAT':
raw_data = zlib.decompress(data)
rows = []
i = 0
for y in range(height):
filtertype = ord(raw_data[i])
i = i + 1
cur = [ord(x) for x in raw_data[i:i+width*4]]
if y == 0:
rgba = self.defilter(cur,None,filtertype,4)
else:
rgba = self.defilter(cur,prev,filtertype,4)
prev = cur
i = i + width * 4
row = []
j = 0
for x in range(width):
self.point(x,y,rgba[j:j+4])
j = j + 4
def defilter(self,cur,prev,filtertype,bpp=3):
if filtertype == 0: # No filter
return cur
elif filtertype == 1: # Sub
xp = 0
for xc in range(bpp,len(cur)):
cur[xc] = (cur[xc] + cur[xp]) % 256
xp = xp + 1
elif filtertype == 2: # Up
for xc in range(len(cur)):
cur[xc] = (cur[xc] + prev[xc]) % 256
elif filtertype == 3: # Average
xp = 0
for xc in range(len(cur)):
cur[xc] = (cur[xc] + (cur[xp] + prev[xc])/2) % 256
xp = xp + 1
elif filtertype == 4: # Paeth
xp = 0
for i in range(bpp):
cur[i] = (cur[i] + prev[i]) % 256
for xc in range(bpp,len(cur)):
a = cur[xp]
b = prev[xc]
c = prev[xp]
p = a + b - c
pa = abs(p - a)
pb = abs(p - b)
pc = abs(p - c)
if pa <= pb and pa <= pc:
value = a
elif pb <= pc:
value = b
else:
value = c
cur[xc] = (cur[xc] + value) % 256
xp = xp + 1
else:
raise TypeError('Unrecognized scanline filter type')
return cur
def chunks(self,f):
while 1:
try:
length = struct.unpack("!I",f.read(4))[0]
tag = f.read(4)
data = f.read(length)
crc = struct.unpack("!i",f.read(4))[0]
except:
return
if zlib.crc32(tag + data) != crc:
raise IOError
yield [tag,data]
#width
#height
#r,g,b,a
#filename
if __name__ == '__main__':
argv = sys.argv
width = int(argv[1])
height = int(argv[2])
c = PNGCanvas(width,height)
c.color = bytearray([0xff,0,0,0xff] )
c.rectangle(0,0,width-1,height-1)
c.verticalGradient(1,1,width-2, height-2,[int(argv[3]),int(argv[4]),int(argv[5]),int(argv[6])],[0x20,0,0xff,0x80])
f = open(argv[7], "wb")
f.write(c.dump())
f.close()