def nextPixelInShape(im, px):
'''
Return a tuple which represents the next coordinate when proceeding
clockwise around a shape. It is an implementation of the square tracing
algorithm, which works as follows:
if on a black square, turn left of previous direction and go forward
if on a white square, turn right of previous direction and go forward
Arguments:
im is of type Image. Contains the image which is being processed.
px is of type tuple. Contains float elements (x, y) which represent the
current coordinate.
'''
global direc, done
pixels = im.load()
try:
pixel = pixel = sum(im.getpixel((px[0], px[1])))
except IndexError:
pixel = sum((255, 255, 255))
# 0 = right, 1 = up, 2 = left, 3 = down
if pixel < sum((127, 127, 127)):
direc = (direc - 1) % 4
else:
direc = (direc + 1) % 4
# Implementation of description in docstring
if direc == 0:
x = px[0] + 1
y = px[1]
elif direc == 1:
x = px[0]
y = px[1] + 1
elif direc == 2:
x = px[0] - 1
y = px[1]
elif direc == 3:
x = px[0]
y = px[1] - 1
try:
pixel = sum(im.getpixel((x, y)))
except IndexError:
pixel = sum((255, 255, 255))
# Since this function returns the next pixel, it can't return an off-shape
# white pixel. It recurses until it finds a black pixel, which it returns.
if pixel < sum((127, 127, 127)):
if (x, y) not in done:
done.append((x, y))
return (x, y)
else:
return nextPixelInShape(im, (x, y))
def nextPixelInShape(im, px):
'''
Return a tuple which represents the next coordinate when proceeding
clockwise around a shape. It is an implementation of the square tracing
algorithm, which works as follows:
if on a black square, turn left of previous direction and go forward
if on a white square, turn right of previous direction and go forward
Arguments:
im is of type Image. Contains the image which is being processed.
px is of type tuple. Contains float elements (x, y) which represent the
current coordinate.
'''
global direc, done
pixels = im.load()
try: pixel = pixel = sum(im.getpixel((px[0], px[1])))
except IndexError: pixel = sum((255, 255, 255))
# 0 = right, 1 = up, 2 = left, 3 = down
if pixel < sum((127, 127, 127)):
direc = (direc - 1) % 4
else:
direc = (direc + 1) % 4
# Implementation of description in docstring
if direc == 0:
x = px[0] + 1
y = px[1]
elif direc == 1:
x = px[0]
y = px[1] + 1
elif direc == 2:
x = px[0] - 1
y = px[1]
elif direc == 3:
x = px[0]
y = px[1] - 1
try: pixel = sum(im.getpixel((x, y)))
except IndexError: pixel = sum((255, 255, 255))
# Since this function returns the next pixel, it can't return an off-shape
# white pixel. It recurses until it finds a black pixel, which it returns.
if pixel < sum((127, 127, 127)):
if (x, y) not in done:
done.append((x, y))
return (x, y)
else:
return nextPixelInShape(im, (x, y))
def readFromRaster(filename):
'''
Return a list of sublists of tuples which correspond to (x, y) coordinates.
Read the coordinates from a raster image, tracing the outline of each shape
in the image.
Arguments:
filename is of type string. Contains name of image file.
'''
global done
# Create Image object from file in local folder
im = initRaster(filename)
# Find first point
point = nextShape(im)
start = point
nextpoint = (0, 0)
i = 0
shapeList = []
# While there are still shapes in the image
while point != (-1, -1):
start = point
shapeList.append([])
shapeList[i].append(point)
# While it has not yet fully traced around the image
while nextpoint != start:
nextpoint = nextPixelInShape(im, point)
point = nextpoint
done.append(point)
shapeList[i].append(point)
i += 1
point = nextShape(im)
# Smooth coordinates in image
shapeList = smoothRasterCoords(shapeList)
# Ensure that each shape starts and ends on the same coordinate
for i in range(len(shapeList)):
if shapeList[i][-1] != shapeList[i][0]:
shapeList[i].append(shapeList[i][0])
return shapeList
def readFromRaster(filename):
'''
Return a list of sublists of tuples which correspond to (x, y) coordinates.
Read the coordinates from a raster image, tracing the outline of each shape
in the image.
Arguments:
filename is of type string. Contains name of image file.
'''
global done
# Create Image object from file in local folder
im = initRaster(filename)
# Find first point
point = nextShape(im)
start = point
nextpoint = (0, 0)
i = 0
shapeList = []
# While there are still shapes in the image
while point != (-1, -1):
start = point
shapeList.append([])
shapeList[i].append(point)
# While it has not yet fully traced around the image
while nextpoint != start:
nextpoint = nextPixelInShape(im, point)
point = nextpoint
done.append(point)
shapeList[i].append(point)
i += 1
point = nextShape(im)
# Smooth coordinates in image
shapeList = smoothRasterCoords(shapeList)
# Ensure that each shape starts and ends on the same coordinate
for i in range(len(shapeList)):
if shapeList[i][-1] != shapeList[i][0]:
shapeList[i].append(shapeList[i][0])
return shapeList
def nextShape(im):
'''
Return a tuple which represents the leftmost point of the next shape.
Arguments:
im is of type Image. Contains the image which is being processed.
'''
global IMDIM, done
# Check the brightness of every point in the image
for x in range(IMDIM):
for y in range(IMDIM):
# If a dark pixel is found that was not already read, return it
if sum(im.getpixel((x, y))) < sum((127, 127, 127)) and\
isOnEdge(im, (x, y)) and not (x, y) in done:
done.append((x, y))
return(x, y)
# If no shape is found, return a special tuple
return (-1, -1)
def nextShape(im):
'''
Return a tuple which represents the leftmost point of the next shape.
Arguments:
im is of type Image. Contains the image which is being processed.
'''
global IMDIM, done
# Check the brightness of every point in the image
for x in range(IMDIM):
for y in range(IMDIM):
# If a dark pixel is found that was not already read, return it
if sum(im.getpixel((x, y))) < sum((127, 127, 127)) and\
isOnEdge(im, (x, y)) and not (x, y) in done:
done.append((x, y))
return(x, y)
# If no shape is found, return a special tuple
return (-1, -1)
