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visiblespectrum.py
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from PIL import Image, ImageDraw, ImageFont
from matplotlib import font_manager
font_addr = font_manager.findfont(font_manager.FontProperties(family='sans'))
def generate_data():
"""
Creates a list of dictionaries
containing data on the visible
portion of the electromagnetic
spectrum.
"""
data = []
c = 3 * 10**8 # speed of light in m/s
h = 6.62607015 * 10**-34 # Planck's constant in Js
for nm in range(380, 781):
item = {}
item["nm"] = nm
item["Hz"] = (c / (nm * 10**-9))
item["THz"] = int(item["Hz"] * 10**-12)
item["rgb"] = _wavelength_to_rgb(nm)
item["J"] = h * item["Hz"]
item["E"] = item["J"] * 10**19
data.append(item)
return data
def print_data(data):
"""
Prints the data structure returned by
generate_data in a table format.
"""
width = 37
pow_minus19 = chr(8315) + chr(185) + chr(8313)
print("-" * width)
print(f"|{chr(955)}(nm)|f(THz)|E(J) |R |G |B |")
print("-" * width)
for item in data:
print(f"|{item['nm']:>5.0f}|", end="")
print(f"{item['THz']:>6.0f}|", end="")
print(f"{item['E']:>4.2f}x10{pow_minus19}|", end="")
print(f"{item['rgb'][0]:>3.0f}|", end="")
print(f"{item['rgb'][1]:>3.0f}|", end="")
print(f"{item['rgb'][2]:>3.0f}|")
print("-" * width)
def plot_wavelength_frequency(data, filename):
"""
Plots the data structure from generate_data
with wavelength on the x-axis and frequency
on the y-axis using an approximation
of the actual colours.
"""
border_width = 70
width_scaling = 2
height_scaling = 0.5
image_width = int(401 * width_scaling) + (border_width * 2)
image_height = int(800 * height_scaling) + (border_width * 2)
column_width = width_scaling
column_bottom = image_height - border_width
x = border_width
image = Image.new("RGB", (image_width, image_height), (32, 32, 32))
image = _draw_labels(image, "Visible Spectrum", "Wavelength (nm)", "Frequency (THz)")
_draw_x_axes(image, border_width, 380, 780, 50)
_draw_y_axes(image, border_width, 0, 800, 50)
draw = ImageDraw.Draw(image)
for item in data:
column_top = column_bottom - (item["THz"] * height_scaling)
draw.rectangle(xy=[x, column_top, x + column_width, column_bottom],
fill=item["rgb"])
x += column_width
try:
image.save(filename, "PNG")
except IOError as e:
print(e)
def plot_frequency_wavelength(data, filename):
"""
Plots the data structure from generate_data
with frequency on the x-axis and wavelength
on the y-axis using an approximation
of the actual colours.
"""
border_width = 70
width_scaling = 2
height_scaling = 0.5
image_width = int(406 * width_scaling) + (border_width * 2)
image_height = int(800 * height_scaling) + (border_width * 2)
column_width = width_scaling
column_bottom = image_height - border_width
x = image_width - border_width
image = Image.new("RGB", (image_width, image_height), (32, 32, 32))
image = _draw_labels(image, "Visible Spectrum", "Frequency (THz)", "Wavelength (nm)")
_draw_x_axes(image, border_width, 384, 789, 50)
_draw_y_axes(image, border_width, 0, 800, 50)
draw = ImageDraw.Draw(image)
for (item, prev) in zip(data, [data[0]] + data[:-1]):
column_top = column_bottom - (item["nm"] * height_scaling)
column_left = image_width - border_width - (data[0]["THz"] - item["THz"] + 1) * width_scaling
column_right = image_width - border_width - (data[0]["THz"] - prev["THz"] + 1) * width_scaling
draw.rectangle(xy=[column_left, column_top, column_right, column_bottom],
fill=item["rgb"])
try:
image.save(filename, "PNG")
except IOError as e:
print(e)
def _draw_labels(image, heading_text, x_axis_text, y_axis_text):
heading_font = ImageFont.truetype(font_addr, 32)
axis_font = ImageFont.truetype(font_addr, 16)
draw = ImageDraw.Draw(image)
heading_text_size = heading_font.getbbox(text=heading_text)
draw.text(xy=((image.width / 2)-(heading_text_size[2] / 2), 8),
text=heading_text,
align="center",
font=heading_font,
fill=(255, 255, 255))
x_axis_text_size = axis_font.getbbox(text=x_axis_text)
draw.text(xy=((image.width / 2) - (x_axis_text_size[2] / 2), image.height - 24),
text=x_axis_text,
font=axis_font,
fill=(255, 255, 255))
image = image.rotate(270, expand=1)
draw = ImageDraw.Draw(image)
y_axis_text_size = axis_font.getbbox(text=y_axis_text)
draw.text(xy=((image.width / 2)-(y_axis_text_size[2] / 2), 8),
text=y_axis_text,
font=axis_font,
fill=(255, 255, 255))
image = image.rotate(90, expand=1)
return image
def _draw_y_axes(image, border_width, y_axis_start, y_axis_end, y_axis_interval):
y_axis_indices_x_left = border_width - 8
y_axis_indices_x_right = border_width
y = image.height - border_width
y_distance = ((image.height - (border_width * 2)) / (y_axis_end - y_axis_start)) * y_axis_interval
index_font = ImageFont.truetype(font_addr, 12)
draw = ImageDraw.Draw(image)
for v in range(y_axis_start, y_axis_end + 1, y_axis_interval):
draw.line(xy=[y_axis_indices_x_left, y, y_axis_indices_x_right, y],
fill=(255, 255, 255),
width=1)
v_str = str(v)
v_str_size = index_font.getbbox(text=v_str)
draw.text(xy=[y_axis_indices_x_left - 2 - (v_str_size[2]), y - (v_str_size[3] / 2)],
text=v_str,
font=index_font,
fill=(255, 255, 255))
y -= y_distance
def _draw_x_axes(image, border_width, x_axis_start, x_axis_end, x_axis_interval):
x_axis_indices_y_top = image.height - border_width
x_axis_indices_y_bottom = x_axis_indices_y_top + 8
x = border_width
x_distance = ((image.width - (border_width * 2)) / (x_axis_end - x_axis_start)) * x_axis_interval
index_font = ImageFont.truetype(font_addr, 12)
draw = ImageDraw.Draw(image)
for v in range(x_axis_start, x_axis_end + 1, x_axis_interval):
draw.line(xy=[x, x_axis_indices_y_bottom, x, x_axis_indices_y_top],
fill=(255, 255, 255),
width=1)
v_str = str(v)
v_str_size = index_font.getbbox(text=v_str)
draw.text(xy=[x - (v_str_size[2] / 2), x_axis_indices_y_bottom + 2],
text=v_str,
font=index_font,
fill=(255, 255, 255))
x += x_distance
def _wavelength_to_rgb(nm):
gamma = 0.8
max_intensity = 255
factor = 0
rgb = {"R": 0, "G": 0, "B": 0}
if 380 <= nm <= 439:
rgb["R"] = -(nm - 440) / (440 - 380)
rgb["G"] = 0.0
rgb["B"] = 1.0
elif 440 <= nm <= 489:
rgb["R"] = 0.0
rgb["G"] = (nm - 440) / (490 - 440)
rgb["B"] = 1.0
elif 490 <= nm <= 509:
rgb["R"] = 0.0
rgb["G"] = 1.0
rgb["B"] = -(nm - 510) / (510 - 490)
elif 510 <= nm <= 579:
rgb["R"] = (nm - 510) / (580 - 510)
rgb["G"] = 1.0
rgb["B"] = 0.0
elif 580 <= nm <= 644:
rgb["R"] = 1.0
rgb["G"] = -(nm - 645) / (645 - 580)
rgb["B"] = 0.0
elif 645 <= nm <= 780:
rgb["R"] = 1.0
rgb["G"] = 0.0
rgb["B"] = 0.0
if 380 <= nm <= 419:
factor = 0.3 + 0.7 * (nm - 380) / (420 - 380)
elif 420 <= nm <= 700:
factor = 1.0
elif 701 <= nm <= 780:
factor = 0.3 + 0.7 * (780 - nm) / (780 - 700)
if rgb["R"] > 0:
rgb["R"] = int(max_intensity * ((rgb["R"] * factor) ** gamma))
else:
rgb["R"] = 0
if rgb["G"] > 0:
rgb["G"] = int(max_intensity * ((rgb["G"] * factor) ** gamma))
else:
rgb["G"] = 0
if rgb["B"] > 0:
rgb["B"] = int(max_intensity * ((rgb["B"] * factor) ** gamma))
else:
rgb["B"] = 0
return (rgb["R"], rgb["G"], rgb["B"])