[course]04 —— 画图 2
1. Draw a Rectangle with create_rectangle(left, top, right, bottom)
def draw(canvas, width, height):
# The first four parameters are the upper-left (x,y)
# and the lower-right (x,y) of the rectangle
canvas.create_rectangle(0,0,150,150)Result: 
2. Graphics Parameters
def draw(canvas, width, height):
# most graphics functions allow you to use optional parameters
# to change the appearance of the object. These are written with the code
# paramName=paramValue
# after the core parameters in the code
# fill changes the internal color of the shape
canvas.create_rectangle( 0, 0, 150, 150, fill="yellow")
# width changes the size of the border
canvas.create_rectangle(100, 50, 250, 100, fill="orange", width=5)
# outline changes the color of the border
canvas.create_rectangle( 50, 100, 150, 200, fill="green",
outline="red", width=3)
# width=0 removes the border entirely
canvas.create_rectangle(125, 25, 175, 190, fill="purple", width=0)Result: 
3.Draw Other Shapes and Text
def draw(canvas, width, height):
# ovals provide the coordinates of the bounding box
canvas.create_oval(100, 50, 300, 150, fill="yellow")
# polygons and lines provide the (x,y) coordinates of each point
# polygons must have 3+ points; lines must have 2+
canvas.create_polygon(100,30,200,50,300,30,200,10, fill="green")
canvas.create_line(100, 50, 300, 150, fill="red", width=5)
# text provides a single (x,y) point, then anchors the text there
# text also requires the text, and can have a font
canvas.create_text(200, 100, text="Amazing!",
fill="purple", font="Helvetica 26 bold underline")
canvas.create_text(200, 100, text="Carpe Diem!", anchor="sw",
fill="darkBlue", font="Times 28 bold italic")Result: 
Other shapes can have optional parameters too. You don't need to know these, but they can be fun to use!
def draw(canvas, width, height):
# smooth lets you make interesting curvy shapes using polygons or lines
canvas.create_polygon(10, 10, 50, 150, 100, 50, smooth=1)
# but if you want to draw an arc, use create_arc
canvas.create_line(10, 10, 50, 150, 100, 50,
width=5, fill="red", smooth=1)
# lines can also add arrows to the end
canvas.create_line(350, 50, 200, 150, arrow=BOTH, fill="blue")
# by default, text is drawn all on one line
# using width breaks the text into multiple lines at that width
canvas.create_text(200, 100, text="Hello World! Isn't it a wonderful day?", width=50, anchor="e")Result: 
4.Draw Custom Colors
def rgbString(red, green, blue):
# Don't worry about how this code works yet.
return "#%02x%02x%02x" % (red, green, blue)
def draw(canvas, width, height):
pistachio = rgbString(147, 197, 114)
maroon = rgbString(176, 48, 96)
canvas.create_rectangle(0, 0, width/2, height/2, fill=pistachio)
canvas.create_rectangle(width/2, height/2, width, height, fill=maroon)Result: 
5. Draw Centered Shapes
def draw(canvas, width, height):
margin = 10
# Approach #1: Add margin to top/left, subtract margin from bottom/right:
canvas.create_rectangle(margin, margin, width-margin, height-margin,
fill="darkGreen")
# Approach #2: add/subtract width/height from center (cx, cy)
(cx, cy) = (width/2, height/2)
(rectWidth, rectHeight) = (width/4, height/4)
canvas.create_rectangle(cx - rectWidth/2, cy - rectHeight/2,
cx + rectWidth/2, cy + rectHeight/2,
fill="orange")Result: 
6. Graphics Helper Functions
def drawBelgianFlag(canvas, x0, y0, x1, y1):
# draw a Belgian flag in the area bounded by (x0,y0) in
# the top-left and (x1,y1) in the bottom-right
width = (x1 - x0)
canvas.create_rectangle(x0, y0, x0+width/3, y1, fill="black", width=0)
canvas.create_rectangle(x0+width/3, y0, x0+width*2/3, y1,
fill="yellow", width=0)
canvas.create_rectangle(x0+width*2/3, y0, x1, y1, fill="red", width=0)
def draw(canvas, width, height):
# Draw a large Belgian flag
drawBelgianFlag(canvas, 25, 25, 175, 150)
# And draw a smaller one below it
drawBelgianFlag(canvas, 75, 160, 125, 200)
# Now let's have some fun and draw a whole grid of Belgian flags!
flagWidth = 30
flagHeight = 25
margin = 5
for row in range(4):
for col in range(6):
left = 200 + col * flagWidth + margin
top = 50 + row * flagHeight + margin
right = left + flagWidth - margin
bottom = top + flagHeight - margin
drawBelgianFlag(canvas, left, top, right, bottom)Result: 
7. Dynamically sizing text
def draw(canvas, width, height):
# Dynamically sizing text is harder, but possible!
# Just compute the font size based on the width or height
# Some guesswork helps to get the ratio right
textSize = width // 10
canvas.create_text(width/2, height/2, text="Hello, World!",
font=f'Arial {textSize} bold')Copy
Result: 
8. Drawing Circular Patterns with Trigonometry
Trig 101
Circle centered at origin
Circle centered at (cx, cy)
Circle centered at (cx, cy) in Python graphics ("up is down!")
Example:
import math
def draw(canvas, width, height):
(cx, cy, r) = (width/2, height/2, min(width, height)/3)
canvas.create_oval(cx-r, cy-r, cx+r, cy+r, fill="yellow")
r *= 0.85 # make smaller so time labels lie inside clock face
for hour in range(12):
hourAngle = math.pi/2 - (2*math.pi)*(hour/12)
hourX = cx + r * math.cos(hourAngle)
hourY = cy - r * math.sin(hourAngle)
label = str(hour if (hour > 0) else 12)
canvas.create_text(hourX, hourY, text=label, font="Arial 16 bold")Result: 
9. Example: Clocks!
import math
def drawClock(canvas, x0, y0, x1, y1, hour, minute):
# draw a clock in the area bounded by (x0,y0) in
# the top-left and (x1,y1) in the bottom-right
# with the given time
# draw an outline rectangle
canvas.create_rectangle(x0, y0, x1, y1, outline="black", width=1)
# find relevant values for positioning clock
width = (x1 - x0)
height = (y1 - y0)
r = min(width, height)/2
cx = (x0 + x1)/2
cy = (y0 + y1)/2
# draw the clock face
canvas.create_oval(cx-r, cy-r, cx+r, cy+r, outline="black", width=2)
# adjust the hour to take the minutes into account
hour += minute/60.0
# find the hourAngle and draw the hour hand
# but we must adjust because 0 is vertical and
# it proceeds clockwise, not counter-clockwise!
hourAngle = math.pi/2 - 2*math.pi*hour/12
hourRadius = r*1/2
hourX = cx + hourRadius * math.cos(hourAngle)
hourY = cy - hourRadius * math.sin(hourAngle)
canvas.create_line(cx, cy, hourX, hourY, fill="black", width=1)
# repeat with the minuteAngle for the minuteHand
minuteAngle = math.pi/2 - 2*math.pi*minute/60
minuteRadius = r*9/10
minuteX = cx + minuteRadius * math.cos(minuteAngle)
minuteY = cy - minuteRadius * math.sin(minuteAngle)
canvas.create_line(cx, cy, minuteX, minuteY, fill="black", width=1)
def draw(canvas, width, height):
# Draw a large clock showing 2:30
drawClock(canvas, 25, 25, 175, 150, 2, 30)
# And draw a smaller one below it showing 7:45
drawClock(canvas, 75, 160, 125, 200, 7, 45)
# Now let's have some fun and draw a whole grid of clocks!
width = 40
height = 40
margin = 5
hour = 0
for row in range(3):
for col in range(4):
left = 200 + col * width + margin
top = 50 + row * height + margin
right = left + width - margin
bottom = top + height - margin
hour += 1
drawClock(canvas, left, top, right, bottom, hour, 0)Result: 
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