def cover_with(self, cover_color):
"""
Mix the two colors respecting their alpha value.
Puts cover_color over itself compositing the colors using the alpha
values.
"""
# fastpath for solid colors
if cover_color.alpha == 255:
return Color(cover_color.red, cover_color.green, cover_color.blue,
cover_color.alpha)
srca = fdiv(cover_color.alpha, 255)
dsta = fdiv(self.alpha, 255)
outa = srca + dsta * (1 - srca)
srcr, srcg, srcb = cover_color.red, cover_color.green, cover_color.blue
dstr, dstg, dstb = self.red, self.green, self.blue
outr = (srcr * srca + dstr * dsta * (1 - srca)) / outa
outg = (srcg * srca + dstg * dsta * (1 - srca)) / outa
outb = (srcb * srca + dstb * dsta * (1 - srca)) / outa
red = int(round(outr))
green = int(round(outg))
blue = int(round(outb))
alpha = int(round(outa * 255))
return Color(red, green, blue, alpha)
def resize(self, source, width, height, resize_canvas=True):
if not resize_canvas:
# this optimised implementation doesn't deal with this.
# so delegate to affine()
return super(Nearest, self).resize(source,
width,
height,
resize_canvas=resize_canvas)
pixels = array.array('B')
pixelsize = source.pixelsize
x_ratio = fdiv(source.width, width) # get the x-axis ratio
y_ratio = fdiv(source.height, height) # get the y-axis ratio
y_range = range(
height) # an iterator over the indices of all lines (y-axis)
x_range = range(
width) # an iterator over the indices of all rows (x-axis)
for y in y_range:
y += 0.5 # use the center of each pixel
source_y = int(y * y_ratio) # get the source line
for x in x_range:
x += 0.5 # use the center of each pixel
source_x = int(x * x_ratio) # get the source row
pixels.extend(source.pixels.get(source_x, source_y))
return get_pixel_array(pixels, width, height, pixelsize)
def cover_with(self, cover_color):
"""
Mix the two colors respecting their alpha value.
Puts cover_color over itself compositing the colors using the alpha
values.
"""
# fastpath for solid colors
if cover_color.alpha == 255:
return Color(cover_color.red, cover_color.green, cover_color.blue, cover_color.alpha)
srca = fdiv(cover_color.alpha, 255)
dsta = fdiv(self.alpha, 255)
outa = srca + dsta * (1 - srca)
srcr, srcg, srcb = cover_color.red, cover_color.green, cover_color.blue
dstr, dstg, dstb = self.red, self.green, self.blue
outr = (srcr * srca + dstr * dsta * (1 - srca)) / outa
outg = (srcg * srca + dstg * dsta * (1 - srca)) / outa
outb = (srcb * srca + dstb * dsta * (1 - srca)) / outa
red = int(round(outr))
green = int(round(outg))
blue = int(round(outb))
alpha = int(round(outa * 255))
return Color(red, green, blue, alpha)
def __init__(self, start_x, start_y, end_x, end_y):
self.start_x = start_x
self.start_y = start_y
self.end_x = end_x
self.end_y = end_y
steep = abs(self.end_y - self.start_y) > abs(self.end_x - self.start_x)
if steep:
x0, y0 = self.start_y, self.start_x
x1, y1 = self.end_y, self.end_x
else:
x0, y0 = self.start_x, self.start_y
x1, y1 = self.end_x, self.end_y
if x0 > x1:
x0, x1 = x1, x0
y0, y1 = y1, y0
self.x0, self.x1, self.y0, self.y1 = x0, x1, y0, y1
delta_x = x1 - x0
delta_y = abs(y1 - y0)
self.error = 0.0
self.delta_error = fdiv(delta_y, delta_x)
if y0 < y1:
self.ystep = 1
else:
self.ystep = -1
self.y = y0
self.iterator = self.steep_iterator if steep else self.normal_iterator
def __init__(self, start_x, start_y, end_x, end_y):
self.start_x = start_x
self.start_y = start_y
self.end_x = end_x
self.end_y = end_y
steep = abs(self.end_y - self.start_y) > abs(self.end_x - self.start_x)
if steep:
x0, y0 = self.start_y, self.start_x
x1, y1 = self.end_y, self.end_x
else:
x0, y0 = self.start_x, self.start_y
x1, y1 = self.end_x, self.end_y
if x0 > x1:
x0, x1 = x1, x0
y0, y1 = y1, y0
self.x0, self.x1, self.y0, self.y1 = x0, x1, y0, y1
delta_x = x1 - x0
delta_y = abs(y1 - y0)
self.error = 0.0
self.delta_error = fdiv(delta_y, delta_x)
if y0 < y1:
self.ystep = 1
else:
self.ystep = -1
self.y = y0
self.iterator = self.steep_iterator if steep else self.normal_iterator
def cover_with(self, base):
"""
Mix the two colors respecting their alpha value.
"""
srca = fdiv(base.alpha, 255)
dsta = fdiv(self.alpha, 255)
outa = srca + dsta * (1 - srca)
srcr, srcg, srcb = base.red, base.green, base.blue
dstr, dstg, dstb = self.red, self.green, self.blue
outr = (srcr * srca + dstr * dsta * (1 - srca)) / outa
outg = (srcg * srca + dstg * dsta * (1 - srca)) / outa
outb = (srcb * srca + dstb * dsta * (1 - srca)) / outa
return Color(*map(int, [outr, outg, outb, outa * 255]))
def nearest(source, width, height, pixelsize):
assert pixelsize == 1, "yea... gotta implement this generically"
pixels = []
pixelappend = pixels.append # cache for cpython
x_ratio = fdiv(source.width, width) # get the x-axis ratio
y_ratio = fdiv(source.height, height) # get the y-axis ratio
y_range = range(height) # an iterator over the indices of all lines (y-axis)
x_range = range(width) # an iterator over the indices of all rows (x-axis)
for y in y_range:
source_y = int(round(y * y_ratio)) # get the source line
line = array.array('B') # initialize a new line
lineappend = line.append # cache for cypthon
for x in x_range:
source_x = int(round(x * x_ratio)) # get the source row
lineappend(source.pixels[source_y][source_x])
pixelappend(line)
return pixels
def nearest(source, width, height, pixelsize):
pixels = []
pixelappend = pixels.append # cache for cpython
x_ratio = fdiv(source.width, width) # get the x-axis ratio
y_ratio = fdiv(source.height, height) # get the y-axis ratio
y_range = range(height) # an iterator over the indices of all lines (y-axis)
x_range = range(width) # an iterator over the indices of all rows (x-axis)
for y in y_range:
source_y = int(round(y * y_ratio)) # get the source line
line = array.array('B') # initialize a new line
lineextend = line.extend # cache for cypthon
for x_coord in x_range:
source_x_coord = int(round(x_coord * x_ratio)) # get the source row
source_x_start = source_x_coord * pixelsize
source_x_end = source_x_start + pixelsize
lineextend(source.pixels[source_y][source_x_start:source_x_end])
pixelappend(line)
return pixels
def iter_pixels(self, color):
"""
Use Bresenham Line Algorithm (http://en.wikipedia.org/wiki/Bresenham's_line_algorithm):
function line(x0, x1, y0, y1)
boolean steep := abs(y1 - y0) > abs(x1 - x0)
if steep then
swap(x0, y0)
swap(x1, y1)
if x0 > x1 then
swap(x0, x1)
swap(y0, y1)
int deltax := x1 - x0
int deltay := abs(y1 - y0)
real error := 0
real deltaerr := deltay / deltax
int ystep
int y := y0
if y0 < y1 then ystep := 1 else ystep := -1
for x from x0 to x1
if steep then plot(y,x) else plot(x,y)
error := error + deltaerr
if error ≥ 0.5 then
y := y + ystep
error := error - 1.0
"""
steep = abs(self.end_y - self.start_y) > abs(self.end_x - self.start_x)
if steep:
x0, y0 = self.start_y, self.start_x
x1, y1 = self.end_y, self.end_x
else:
x0, y0 = self.start_x, self.start_y
x1, y1 = self.end_x, self.end_y
if x0 > x1:
x0, x1 = x1, x0
y0, y1 = y1, y0
delta_x = x1 - x0
delta_y = abs(y1 - y0)
error = 0.0
delta_error = fdiv(delta_y, delta_x)
if y0 < y1:
ystep = 1
else:
ystep = -1
y = y0
for x in range(x0, x1):
if steep:
yield y, x, color
else:
yield x, y, color
error += delta_error
if error >= 0.5:
y = y + ystep
error = error - 1.0
def resize(self, source, width, height, resize_canvas=True):
if not resize_canvas:
# this optimised implementation doesn't deal with this.
# so delegate to affine()
return super(Nearest, self).resize(
source, width, height, resize_canvas=resize_canvas
)
pixels = array.array('B')
pixelsize = source.pixelsize
x_ratio = fdiv(source.width, width) # get the x-axis ratio
y_ratio = fdiv(source.height, height) # get the y-axis ratio
y_range = range(height) # an iterator over the indices of all lines (y-axis)
x_range = range(width) # an iterator over the indices of all rows (x-axis)
for y in y_range:
y += 0.5 # use the center of each pixel
source_y = int(y * y_ratio) # get the source line
for x in x_range:
x += 0.5 # use the center of each pixel
source_x = int(x * x_ratio) # get the source row
pixels.extend(source.pixels.get(source_x, source_y))
return get_pixel_array(pixels, width, height, pixelsize)
def init(self):
if self.current_pass > self.LAST_PASS:
self.done = True
return
self.xstart, self.ystart, self.xstep, self.ystep = self.passes[self.current_pass]
self.pixels_per_row = int(math.ceil(fdiv(self.reader.width - self.xstart, self.xstep)))
self.row_bytes = int(math.ceil(self.reader.psize * self.pixels_per_row))
self.reader.scanline_length = self.get_scanline_length()
if self.ystart >= self.reader.height:
# empty pass
self.next_pass()
elif self.xstart >= self.reader.width:
# empty pass
self.next_pass()
else:
self.yiter = irange(self.ystart, self.reader.height, self.ystep)
self.current_y = next(self.yiter)
def init(self):
if self.current_pass > self.LAST_PASS:
self.done = True
return
self.xstart, self.ystart, self.xstep, self.ystep = self.passes[
self.current_pass]
self.pixels_per_row = int(
math.ceil(fdiv(self.reader.width - self.xstart, self.xstep)))
self.row_bytes = int(
math.ceil(self.reader.pixelsize * self.pixels_per_row))
self.reader.scanline_length = self.get_scanline_length()
if self.ystart >= self.reader.height:
# empty pass
self.next_pass()
elif self.xstart >= self.reader.width:
# empty pass
self.next_pass()
else:
self.yiter = irange(self.ystart, self.reader.height, self.ystep)
self.current_y = next(self.yiter)
def _mixin_alpha(colors, alpha):
from pymaging.utils import fdiv
ratio = fdiv(alpha, 255)
return [int(round(color * ratio)) for color in colors]
def iter_pixels(self, color):
"""
Use Xiaolin Wu's line algorithm: http://en.wikipedia.org/wiki/Xiaolin_Wu%27s_line_algorithm
function plot(x, y, c) is
plot the pixel at (x, y) with brightness c (where 0 ≤ c ≤ 1)
function ipart(x) is
return integer part of x
function round(x) is
return ipart(x + 0.5)
function fpart(x) is
return fractional part of x
function rfpart(x) is
return 1 - fpart(x)
function drawLine(x1,y1,x2,y2) is
dx = x2 - x1
dy = y2 - y1
if abs(dx) < abs(dy) then
swap x1, y1
swap x2, y2
swap dx, dy
end if
if x2 < x1
swap x1, x2
swap y1, y2
end if
gradient = dy / dx
// handle first endpoint
xend = round(x1)
yend = y1 + gradient * (xend - x1)
xgap = rfpart(x1 + 0.5)
xpxl1 = xend // this will be used in the main loop
ypxl1 = ipart(yend)
plot(xpxl1, ypxl1, rfpart(yend) * xgap)
plot(xpxl1, ypxl1 + 1, fpart(yend) * xgap)
intery = yend + gradient // first y-intersection for the main loop
// handle second endpoint
xend = round (x2)
yend = y2 + gradient * (xend - x2)
xgap = fpart(x2 + 0.5)
xpxl2 = xend // this will be used in the main loop
ypxl2 = ipart (yend)
plot (xpxl2, ypxl2, rfpart (yend) * xgap)
plot (xpxl2, ypxl2 + 1, fpart (yend) * xgap)
// main loop
for x from xpxl1 + 1 to xpxl2 - 1 do
plot (x, ipart (intery), rfpart (intery))
plot (x, ipart (intery) + 1, fpart (intery))
intery = intery + gradient
end function
"""
def _plot(x, y, c):
"""
plot the pixel at (x, y) with brightness c (where 0 ≤ c ≤ 1)
"""
return int(x), int(y), color.get_for_brightness(c)
dx = self.end_x - self.start_x
dy = self.end_y - self.start_y
x1, x2, y1, y2 = self.start_x, self.end_x, self.start_y, self.end_y
if abs(dx) > abs(dy):
x1, y1 = y1, x1
x2, y2 = y2, x2
dx, dy = dy, dx
if x2 < x1:
x1, x2 = x2, x1
y1, y2 = y2, y1
gradient = fdiv(dy, dx)
xend = round(x1)
yend = y1 + gradient * (xend - x1)
xgap = _rfpart(x1 + 0.5)
xpxl1 = xend
ypxl1 = _ipart(yend)
yield _plot(xpxl1, ypxl1, _rfpart(yend) * xgap)
yield _plot(xpxl1, ypxl1 + 1, _fpart(yend) * xgap)
intery = yend + gradient
xend = _round(x2)
yend = y2 + gradient * (xend - x2)
xgap = _fpart(x2 + 0.5)
xpxl2 = xend
ypxl2 = _ipart(yend)
yield _plot(xpxl2, ypxl2, _rfpart(yend) * xgap)
yield _plot(xpxl2, ypxl2 + 1, _fpart(yend) * xgap)
for x in range(xpxl1 + 1, xpxl2 - 1):
yield _plot(x, _ipart(intery), _rfpart(intery))
yield _plot(x, _ipart(intery) + 1, _fpart(intery))
intery += gradient
def _mixin_alpha(colors, alpha):
ratio = fdiv(alpha, 255)
return [int(round(color * ratio)) for color in colors]
def _mixin_alpha(colors, alpha):
ratio = fdiv(alpha, 255)
return [int(round(color * ratio)) for color in colors]
def handle_chunk_IHDR(self, chunk, length):
# http://www.w3.org/TR/PNG/#11IHDR
if length != 13:
raise ChunkError('IHDR chunk has incorrect length %s, should be 13.' % length)
(self.width, self.height, self.bit_depth, self.color_type,
self.compression_method, self.filter_method,
self.interlace_method) = struct.unpack("!2I5B", chunk)
# Check that the header specifies only valid combinations.
if self.bit_depth not in ALLOWED_BIT_DEPTHS:
raise PNGReaderError("invalid bit depth %d" % self.bit_depth)
if self.color_type not in ALLOWED_COLOR_TYPES:
raise PNGReaderError("invalid colour type %d" % self.color_type)
# Check indexed (palettized) images have 8 or fewer bits
# per pixel; check only indexed or greyscale images have
# fewer than 8 bits per pixel.
if ((self.color_type & 1 and self.bit_depth > 8) or
(self.bit_depth < 8 and self.color_type not in (0,3))):
raise PNGReaderError("Illegal combination of bit depth (%d)"
" and colour type (%d)."
" See http://www.w3.org/TR/2003/REC-PNG-20031110/#table111 ."
% (self.bit_depth, self.color_type))
if self.compression_method != 0:
raise PNGReaderError("unknown compression method %d" % self.compression_method)
if self.filter_method != 0:
raise PNGReaderError("Unknown filter method %d,"
" see http://www.w3.org/TR/2003/REC-PNG-20031110/#9Filters ."
% self.filter_method)
if self.interlace_method not in (0, 1):
raise PNGReaderError("Unknown interlace method %d,"
" see http://www.w3.org/TR/2003/REC-PNG-20031110/#8InterlaceMethods ."
% self.interlace_method)
# Derived values
# http://www.w3.org/TR/PNG/#6Colour-values
colormap = bool(self.color_type & 1)
greyscale = not (self.color_type & 2)
alpha = bool(self.color_type & 4)
if greyscale or colormap:
color_planes = 1
else:
color_planes = 3
planes = color_planes + alpha
self.colormap = colormap
self.greyscale = greyscale
self.alpha = alpha
self.color_planes = color_planes
self.planes = planes
self.psize = fdiv(self.bit_depth, 8) * planes
if int(self.psize) == self.psize:
self.psize = int(self.psize)
self.filter_unit = max(1, self.psize)
self.row_bytes = int(math.ceil(self.width * self.psize))
# scanline stuff
self.scanline = array('B')
if self.bit_depth == 16:
array_code = 'H'
else:
array_code = 'B'
if self.interlace_method:
self.adam7 = Adam7(self)
self.pixels = [array(array_code, [0] * self.width * self.psize) for _ in range(self.height)]
self.scanline_length = self.adam7.get_scanline_length()
self._process_scanline = self._process_interlaced_scanline
else:
self.previous_scanline = None
self.pixels = []
self.scanline_length = self.row_bytes + 1
self._process_scanline = self._process_straightlaced_scanline
def handle_chunk_IHDR(self, chunk, length):
# http://www.w3.org/TR/PNG/#11IHDR
if length != 13:
raise ChunkError(
'IHDR chunk has incorrect length %s, should be 13.' % length)
(self.width, self.height, self.bit_depth, self.color_type,
self.compression_method, self.filter_method,
self.interlace_method) = struct.unpack("!2I5B", chunk)
# Check that the header specifies only valid combinations.
if self.bit_depth not in ALLOWED_BIT_DEPTHS:
raise PNGReaderError("invalid bit depth %d" % self.bit_depth)
if self.color_type not in ALLOWED_COLOR_TYPES:
raise PNGReaderError("invalid colour type %d" % self.color_type)
# Check indexed (palettized) images have 8 or fewer bits
# per pixel; check only indexed or greyscale images have
# fewer than 8 bits per pixel.
if ((self.color_type & 1 and self.bit_depth > 8)
or (self.bit_depth < 8 and self.color_type not in (0, 3))):
raise PNGReaderError(
"Illegal combination of bit depth (%d)"
" and colour type (%d)."
" See http://www.w3.org/TR/2003/REC-PNG-20031110/#table111 ." %
(self.bit_depth, self.color_type))
if self.compression_method != 0:
raise PNGReaderError("unknown compression method %d" %
self.compression_method)
if self.filter_method != 0:
raise PNGReaderError(
"Unknown filter method %d,"
" see http://www.w3.org/TR/2003/REC-PNG-20031110/#9Filters ." %
self.filter_method)
if self.interlace_method not in (0, 1):
raise PNGReaderError(
"Unknown interlace method %d,"
" see http://www.w3.org/TR/2003/REC-PNG-20031110/#8InterlaceMethods ."
% self.interlace_method)
self.pixelsize = {
0: 1,
2: 3,
3: 1,
4: 2,
6: 4,
}[self.color_type]
# Derived values
# http://www.w3.org/TR/PNG/#6Colour-values
colormap = bool(self.color_type & 1)
greyscale = not (self.color_type & 2)
alpha = bool(self.color_type & 4)
if greyscale or colormap:
color_planes = 1
else:
color_planes = 3
planes = color_planes + alpha
self.colormap = colormap
self.greyscale = greyscale
self.alpha = alpha
self.mode = RGBA if self.alpha else RGB
self.color_planes = color_planes
self.planes = planes
self.psize = fdiv(self.bit_depth, 8) * planes
if int(self.psize) == self.psize:
self.psize = int(self.psize)
self.filter_unit = max(1, self.psize)
self.row_bytes = int(math.ceil(self.width * self.psize))
# scanline stuff
self.scanline = array.array('B')
if self.bit_depth == 16:
array_code = 'H'
else:
array_code = 'B'
data = array.array(array_code,
[0] * self.width * self.height * self.pixelsize)
self.pixels = get_pixel_array(data, self.width, self.height,
self.pixelsize)
if self.interlace_method:
self.adam7 = Adam7(self)
self.scanline_length = self.adam7.get_scanline_length()
self._process_scanline = self._process_interlaced_scanline
else:
self.previous_scanline = None
self.scanline_length = self.row_bytes + 1
self.current_y = 0
self._process_scanline = self._process_straightlaced_scanline
def resize(self, source, width, height, resize_canvas=True):
if not resize_canvas:
# this optimised implementation doesn't deal with this.
# so delegate to affine()
return super(Bilinear, self).resize(
source, width, height, resize_canvas=resize_canvas
)
x_ratio = fdiv(source.width, width) # get the x-axis ratio
y_ratio = fdiv(source.height, height) # get the y-axis ratio
pixelsize = source.pixelsize
pixels = array.array('B')
if source.palette:
raise NotImplementedError("Resampling of paletted images is not yet supported")
if x_ratio < 1 and y_ratio < 1:
if not (width % source.width) and not (height % source.height):
# optimisation: if doing a perfect upscale,
# can just use nearest neighbor (it's much faster)
return nearest.resize(source, width, height)
has_alpha = source.mode.alpha
color_channels_range = range(pixelsize - 1 if has_alpha else pixelsize)
y_range = range(height) # an iterator over the indices of all lines (y-axis)
x_range = range(width) # an iterator over the indices of all rows (x-axis)
for y in y_range:
src_y = (y + 0.5) * y_ratio - 0.5 # use the center of each pixel
src_y_i = int(src_y)
weight_y0 = 1 - abs(src_y - src_y_i)
for x in x_range:
src_x = (x + 0.5) * x_ratio - 0.5
src_x_i = int(src_x)
weight_x0 = 1 - abs(src_x - src_x_i)
channel_sums = [0.0] * pixelsize
# populate <=4 nearest src_pixels, taking care not to go off
# the edge of the image.
src_pixels = [source.get_color(src_y_i, src_x_i), None, None, None]
if src_x_i + 1 < source.width:
src_pixels[1] = source.get_color(src_y_i, src_x_i + 1)
else:
weight_x0 = 1
if src_y_i + 1 < source.height:
src_pixels[2] = source.get_color(src_y_i + 1, src_x_i)
if src_x_i + 1 < source.height:
src_pixels[3] = source.get_color(src_y_i + 1, src_x_i + 1)
else:
weight_y0 = 1
for i, src_pixel in enumerate(src_pixels):
if src_pixel is None:
continue
src_pixel = src_pixel.to_pixel(pixelsize)
weight_x = (1 - weight_x0) if (i % 2) else weight_x0
weight_y = (1 - weight_y0) if (i // 2) else weight_y0
alpha_weight = weight_x * weight_y
color_weight = alpha_weight
alpha = 255
if has_alpha:
alpha = src_pixel[-1]
if not alpha:
continue
color_weight *= (alpha / 255.0)
for channel_index, channel_value in zip(color_channels_range, src_pixel):
channel_sums[channel_index] += color_weight * channel_value
if has_alpha:
channel_sums[-1] += alpha_weight * alpha
if has_alpha:
total_alpha_multiplier = channel_sums[-1] / 255.0
if total_alpha_multiplier: # (avoid div/0)
for channel_index in color_channels_range:
channel_sums[channel_index] /= total_alpha_multiplier
pixels.extend([int(round(s)) for s in channel_sums])
return get_pixel_array(pixels, width, height, pixelsize)
def iter_pixels(self, color):
"""
Use Xiaolin Wu's line algorithm: http://en.wikipedia.org/wiki/Xiaolin_Wu%27s_line_algorithm
function plot(x, y, c) is
plot the pixel at (x, y) with brightness c (where 0 ≤ c ≤ 1)
function ipart(x) is
return integer part of x
function round(x) is
return ipart(x + 0.5)
function fpart(x) is
return fractional part of x
function rfpart(x) is
return 1 - fpart(x)
function drawLine(x1,y1,x2,y2) is
dx = x2 - x1
dy = y2 - y1
if abs(dx) < abs(dy) then
swap x1, y1
swap x2, y2
swap dx, dy
end if
if x2 < x1
swap x1, x2
swap y1, y2
end if
gradient = dy / dx
// handle first endpoint
xend = round(x1)
yend = y1 + gradient * (xend - x1)
xgap = rfpart(x1 + 0.5)
xpxl1 = xend // this will be used in the main loop
ypxl1 = ipart(yend)
plot(xpxl1, ypxl1, rfpart(yend) * xgap)
plot(xpxl1, ypxl1 + 1, fpart(yend) * xgap)
intery = yend + gradient // first y-intersection for the main loop
// handle second endpoint
xend = round (x2)
yend = y2 + gradient * (xend - x2)
xgap = fpart(x2 + 0.5)
xpxl2 = xend // this will be used in the main loop
ypxl2 = ipart (yend)
plot (xpxl2, ypxl2, rfpart (yend) * xgap)
plot (xpxl2, ypxl2 + 1, fpart (yend) * xgap)
// main loop
for x from xpxl1 + 1 to xpxl2 - 1 do
plot (x, ipart (intery), rfpart (intery))
plot (x, ipart (intery) + 1, fpart (intery))
intery = intery + gradient
end function
"""
def _plot(x, y, c):
"""
plot the pixel at (x, y) with brightness c (where 0 ≤ c ≤ 1)
"""
return int(x), int(y), color.get_for_brightness(c)
dx = self.end_x - self.start_x
dy = self.end_y - self.start_y
x1, x2, y1, y2 = self.start_x, self.end_x, self.start_y, self.end_y
if abs(dx) > abs(dy):
x1, y1 = y1, x1
x2, y2 = y2, x2
dx, dy = dy, dx
if x2 < x1:
x1, x2 = x2, x1
y1, y2 = y2, y1
gradient = fdiv(dy, dx)
xend = round(x1)
yend = y1 + gradient * (xend - x1)
xgap = _rfpart(x1 + 0.5)
xpxl1 = xend
ypxl1 = _ipart(yend)
yield _plot(xpxl1, ypxl1, _rfpart(yend) * xgap)
yield _plot(xpxl1, ypxl1 + 1, _fpart(yend) * xgap)
intery = yend + gradient
xend = _round(x2)
yend = y2 + gradient * (xend - x2)
xgap = _fpart(x2 + 0.5)
xpxl2 = xend
ypxl2 = _ipart(yend)
yield _plot(xpxl2, ypxl2, _rfpart(yend) * xgap)
yield _plot(xpxl2, ypxl2 + 1, _fpart(yend) * xgap)
for x in range (xpxl1 + 1, xpxl2 - 1):
yield _plot(x, _ipart(intery), _rfpart(intery))
yield _plot(x, _ipart(intery) + 1, _fpart(intery))
intery += gradient
