先载入必备的包：
from tkinter import Tk, ttk, PhotoImage, Canvas
from tkinter import Menu, StringVar, filedialog, Listbox
1 一个可以滚动的画布
class App(Tk):
def __init__(self):
super().__init__()
self._set_scroll()
self._create_canvas()
self._scroll_command()
self._create_button()
self.canvas.create_window((0, 0), window=self.frame,
anchor='nw')
self.layout()
self.bind("<Configure>", self.resize)
self.update_idletasks()
self.minsize(self.winfo_width(), self.winfo_height())
def _set_scroll(self):
self.scroll_x = ttk.Scrollbar(orient='horizontal')
self.scroll_y = ttk.Scrollbar(orient='vertical')
def _create_canvas(self):
self.canvas = Canvas(width=300, height=100,
xscrollcommand=self.scroll_x.set,
yscrollcommand=self.scroll_y.set)
def _scroll_command(self):
self.scroll_x['command'] = self.canvas.xview
self.scroll_y['command'] = self.canvas.yview
def _create_button(self):
self.frame = ttk.Frame(self.canvas)
self.button = ttk.Button(self.frame, text="载入图片",
command=self.load_image)
def layout(self):
self.button.grid()
self.canvas.grid(row=0, column=0, sticky="nswe")
self.scroll_x.grid(row=1, column=0, sticky="we")
self.scroll_y.grid(row=0, column=1, sticky="ns")
self.rowconfigure(0, weight=1)
self.columnconfigure(0, weight=1)
def resize(self, event):
region = self.canvas.bbox('all')
self.canvas.configure(scrollregion=region)
def load_image(self):
self.button.destroy()
self.image = PhotoImage(file="python.gif")
ttk.Label(self.frame, image=self.image).grid()
if __name__ == "__main__":
app = App()
app.mainloop()
create_window 方法将框架添加到可滚动画布。第一个参数是放置与窗口选项一起传递的小部件的位置。由于 Canvas 小控件的 x 轴和 y 轴从左上角开始，因此我们将框架置于 位置，并且还将其与该角对齐，并带有
anchor='nw'。当主窗口调整大小时，绑定到 <Configure> 事件将帮助我们正确重新配置画布。为了获得容器的实际大小，我们必须强制几何管理器通过调用update_idletasks 来绘制所有子小部件。此方法在所有小部件类中都可用，并强制 Tkinter 处理所有挂起的空闲事件，如重新绘制和几何重新计算。要轻松重新计算，可以使用 bbox 方法与 all 常数。这将返回整个"canvas"微件的边界框。
效果图：
图1 提供载入图片的按钮
点击按钮将销毁按钮并载入图片，可以使用滑块查看图片：
图2 点击按钮载入图片
2 显示鼠标的坐标
class App(Tk):
def __init__(self):
super().__init__()
self.title("canvas 基础")
self.canvas = Canvas(bg="white")
self.label = ttk.Label()
self.canvas.bind("<Motion>", self.mouse_motion)
self.canvas.grid()
self.label.grid()
def mouse_motion(self, event):
self.label['text'] = f"鼠标位置: ({event.x}, {event.y})"
if __name__ == "__main__":
app = App()
app.mainloop()
效果图：
图2 显示鼠标的位置
3 画线
class LineForm(ttk.LabelFrame):
arrows = ('none', 'first', 'last', 'both')
colors = ("black", "red", "blue", "green")
def __init__(self, master=None, **kw):
super().__init__(master, text="线条的选择", **kw)
self.create_var()
self.set_arrow()
self.set_color()
self.set_line()
self.layout()
self.arrow.set(self.arrows[0])
self.color.set(self.colors[0])
self.line_width.set(1)
def create_var(self):
self.arrow = StringVar()
self.color = StringVar()
def set_arrow(self):
self.arrow_label = ttk.Label(self, text="Arrow style")
self.arrow_option = ttk.OptionMenu(self, self.arrow, *self.arrows)
def set_color(self):
self.color_label = ttk.Label(self, text="Fill color")
self.color_option = ttk.OptionMenu(self, self.color, *self.colors)
def set_line(self):
self.line_width_label = ttk.Label(self, text="Line width")
self.line_width = ttk.Spinbox(self, from_=1, to=5, width=5)
def layout(self):
self.arrow_label.grid(sticky='w', row=0, column=0)
self.arrow_option.grid(row=0, column=1, pady=10)
self.color_label.grid(sticky='w', row=1, column=0)
self.color_option.grid(row=1, column=1, pady=10)
self.line_width_label.grid(sticky='w', row=2, column=0)
self.line_width.grid(row=2, column=1, pady=10)
def get_value(self, var_name):
if var_name == 'arrow':
return self.arrow.get()
elif var_name == 'color':
return self.color.get()
elif var_name == 'line_width':
return int(self.line_width.get())
class App(Tk):
def __init__(self):
super().__init__()
self.title("Basic canvas")
self.line_start = None
self.form = LineForm()
self.canvas = Canvas(bg="white")
self.canvas.bind("<Button-1>", self.draw)
self.form.grid(row=0, column=0, padx=10, pady=10)
self.canvas.grid(row=0, column=1)
def draw(self, event):
x, y = event.x, event.y
if not self.line_start:
self.line_start = (x, y)
else:
x_origin, y_origin = self.line_start
self.line_start = None
line = (x_origin, y_origin, x, y)
arrow, color, width = [self.form.get_value(name)
for name in ('arrow', 'color', 'line_width')]
self.canvas.create_line(*line, arrow=arrow,
fill=color, width=width)
if __name__ == "__main__":
app = App()
app.mainloop()
显示效果：
图3 不同格式的线
4 画出文本
class App(Tk):
def __init__(self):
super().__init__()
self.title("Canvas text items")
self.geometry("300x100")
self.var = StringVar()
self.entry = ttk.Entry(self, textvariable=self.var)
self.canvas = Canvas(self, bg="white")
self.entry.pack(pady=5)
self.canvas.pack()
self.update()
w, h = self.canvas.winfo_width(), self.canvas.winfo_height()
options = {"font": "courier", "fill": "blue",
"activefill": "red"}
self.text_id = self.canvas.create_text((w/2, h/2), **options)
self.var.trace("w", self.write_text)
def write_text(self, *args):
self.canvas.itemconfig(self.text_id, text=self.var.get())
if __name__ == "__main__":
app = App()
app.mainloop()
图4 画出文本
画出不同的形状
class App(Tk):
shapes = ("rectangle", "oval", "arc")
def __init__(self):
super().__init__()
self.title("Drawing standard items")
style = ttk.Style()
style.map("C.TButton",
foreground=[('pressed', 'red'), ('active', 'blue')],
background=[('pressed', '!disabled', 'black'),
('active', 'white')],
relief=[('pressed', '!disabled', 'sunken')]
)
self.start = None
self.shape = None
self.canvas = Canvas(self, bg="white")
frame = ttk.Frame(self)
for shape in self.shapes:
btn = ttk.Button(frame, text=shape.capitalize(), style="C.TButton")
btn.config(command=partial(self.set_selection, shape))
btn.pack(side='left', expand=True, fill='both')
self.canvas.bind("<Button-1>", self.draw_item)
self.canvas.pack()
frame.pack(fill='both')
def set_selection(self, shape):
self.shape = shape
def draw_item(self, event):
x, y = event.x, event.y
if not self.start:
self.start = (x, y)
else:
x_origin, y_origin = self.start
self.start = None
bbox = (x_origin, y_origin, x, y)
if self.shape == "rectangle":
self.canvas.create_rectangle(*bbox, fill="blue",
activefill="yellow")
elif self.shape == "oval":
self.canvas.create_oval(*bbox, fill="red",
activefill="yellow")
elif self.shape == "arc":
self.canvas.create_arc(*bbox, fill="green",
activefill="yellow")
if __name__ == "__main__":
app = App()
app.mainloop()
图5 点击不同按钮画不同的图形
设置图形可用鼠标隐藏的操作
root = Tk()
canvas = Canvas(root)
canvas.create_rectangle(10, 10, 200, 200, fill='red', tags='rect')
canvas.create_rectangle(100, 100, 300, 300, fill='blue', tags='rect1')
def set_hidden(event):
canvas.itemconfigure('rect1', state = 'hidden')
canvas.tag_bind('rect1', '<1>', set_hidden)
canvas.grid()
root.mainloop()
当您使用鼠标左键将会把蓝色的矩形隐藏。
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