python - Tkinter:在 Canvas 上缩放项目

Question

我试图了解 Canvas 缩放的工作原理。

例如，下面的代码。为什么绑定(bind)到鼠标滚轮的 canvas.scale("all", ...) 正在缩放所有矩形而不是文本。

如何实现文本与矩形一起缩放？

import Tkinter as tk
import random

pressed = False

class Example(tk.Frame):
    def __init__(self, root):
        tk.Frame.__init__(self, root)
        self.canvas = tk.Canvas(self, width=400, height=400, background="bisque")
        self.xsb = tk.Scrollbar(self, orient="horizontal", command=self.canvas.xview)
        self.ysb = tk.Scrollbar(self, orient="vertical", command=self.canvas.yview)
        self.canvas.configure(yscrollcommand=self.ysb.set, xscrollcommand=self.xsb.set)
        self.canvas.configure(scrollregion=(0,0,1000,1000))

        self.xsb.grid(row=1, column=0, sticky="ew")
        self.ysb.grid(row=0, column=1, sticky="ns")
        self.canvas.grid(row=0, column=0, sticky="nsew")
        self.grid_rowconfigure(0, weight=1)
        self.grid_columnconfigure(0, weight=1)

        #Plot some rectangles
        for n in range(50):
            x0 = random.randint(0, 900)
            y0 = random.randint(50, 900)
            x1 = x0 + random.randint(50, 100)
            y1 = y0 + random.randint(50,100)
            color = ("red", "orange", "yellow", "green", "blue")[random.randint(0,4)]
            self.canvas.create_rectangle(x0,y0,x1,y1, outline="black", fill=color, activefill="black", tags=n)
        self.canvas.create_text(50,10, anchor="nw", text="Click and drag to move the canvas\nScroll to zoom.")

        # This is what enables using the mouse:
        self.canvas.bind("<ButtonPress-1>", self.move_start)
        self.canvas.bind("<B1-Motion>", self.move_move)

        self.canvas.bind("<ButtonPress-2>", self.pressed2)
        self.canvas.bind("<Motion>", self.move_move2)

        #linux scroll
        self.canvas.bind("<Button-4>", self.zoomerP)
        self.canvas.bind("<Button-5>", self.zoomerM)
        #windows scroll
        self.canvas.bind("<MouseWheel>",self.zoomer)
        # Hack to make zoom work on Windows
        root.bind_all("<MouseWheel>",self.zoomer)

    #move
    def move_start(self, event):
        self.canvas.scan_mark(event.x, event.y)
    def move_move(self, event):
        self.canvas.scan_dragto(event.x, event.y, gain=1)

    #move
    def pressed2(self, event):
        global pressed
        pressed = not pressed
        self.canvas.scan_mark(event.x, event.y)
    def move_move2(self, event):
        if pressed:   
            self.canvas.scan_dragto(event.x, event.y, gain=1)        

    #windows zoom
    def zoomer(self,event):
        if (event.delta > 0):
            self.canvas.scale("all", event.x, event.y, 1.1, 1.1)
        elif (event.delta < 0):
            self.canvas.scale("all", event.x, event.y, 0.9, 0.9)
        self.canvas.configure(scrollregion = self.canvas.bbox("all"))

    #linux zoom
    def zoomerP(self,event):
        self.canvas.scale("all", event.x, event.y, 1.1, 1.1)
        self.canvas.configure(scrollregion = self.canvas.bbox("all"))
    def zoomerM(self,event):
        self.canvas.scale("all", event.x, event.y, 0.9, 0.9)
        self.canvas.configure(scrollregion = self.canvas.bbox("all"))

if __name__ == "__main__":
    root = tk.Tk()
    Example(root).pack(fill="both", expand=True)
    root.mainloop()

Answer 1

文本缩放并不是“真正”的文本缩放。这是(至少对于 Canvas-widget)字体的改变。

来自documentation :

This method will not change the size of a text item, but may move it.

编辑:此行为也适用于图像(使用 Tkinter.Canvas.create_image(...) 创建)和窗口(使用 Tkinter.Canvas.create_window(...) 创建) .由于文档将缩放定义为

.scale(tagOrId, xOffset, yOffset, xScale, yScale)

Scale all objects according to their distance from a point P=(xOffset, yOffset). The scale factors xScale and yScale are based on a value of 1.0, which means no scaling. Every point in the objects selected by tagOrId is moved so that its x distance from P is multiplied by xScale and its y distance is multiplied by yScale.

请注意缩放如何工作的 斜体部分。

结束编辑

如果您想增加字体大小，您需要使用 itemconfigure 方法自行配置所有文本元素。

要以非常实用的方式实现它，您可以使用 tags 来标识所有文本元素。如果您首先获取字体大小 (itemcget)，然后根据比例因子增加它，则不仅可以绝对增加，还可以相对增加。