Kivy：图像的绝对位置和大小

Question

使用Kivy，如何找到图像的位置和大小？

以下代码将位置打印为[0,72]，图像尺寸打印为[800，480]。我怀疑这分别是BoxLayout的位置和大小。如果我们在下面使用Mels图片，很明显位置和大小都不正确。

from kivy.uix.boxlayout import BoxLayout
from kivy.lang import Builder
from kivy.app import App
from kivy.uix.screenmanager import ScreenManager, Screen

Builder.load_string("""

<MyScreenManager>:
    ThirdScreen:
        id: third_screen

<ThirdScreen>:
    name: '_third_screen_'
    id: third_screen
    BoxLayout:
        orientation: "vertical"
        id: third_screen_boxlayout
        canvas:
        Label:
            id: main_title
            text: "Title"
            size_hint: (1, 0.1)
        Image:
            id: main_image
            source: "C:/Users/OneDrive/0. T2/6. Kivy/4/claymore.jpg"
        BoxLayout:
            id: button_boxlayout
            orientation: "horizontal"
            padding: 10
            size_hint: (1, 0.15)
            Button:
                id: accept_button
                text: "Okay"
                size_hint: (0.33, 1)
                on_press: root.image_accepted_by_user(root.image_address)
            Button:
                id: crop_button
                text: "Crop"
                size_hint: (0.33, 1)
                on_press: root.enable_cropping()
            Button:
                id: cancel_button
                text: "Cancel"
                size_hint: (0.33, 1) 
                on_press: root.manager.current = '_first_screen_'
""")


class ThirdScreen(Screen, BoxLayout):
    def enable_cropping(self):
        print(self.ids.main_image.pos)
        print(self.ids.main_image.size)

# Create the screen manager
sm = ScreenManager()
sm.add_widget(ThirdScreen(name='_third_screen_'))

class MyApp(App):
    def build(self):
        return sm


if __name__ == '__main__':
    MyApp().run()

Answer 1

绝对位置和大小

• 绝对大小，请使用self.ids.main_image.norm_image_size
• 绝对位置x，使用self.ids.main_image.center_x - self.ids.main_image.norm_image_size[0] / 2.
• 绝对位置，使用self.ids.main_image.center_y - self.ids.main_image.norm_image_size[1] / 2.

摘要

class ThirdScreen(Screen):
    def enable_cropping(self):
        print("\nThirdScreen:")
        print(self.ids.main_image.pos)
        print(self.ids.main_image.size)
        print("\tAbsolute size=", self.ids.main_image.norm_image_size)
        print("\tAbsolute pos_x=", self.ids.main_image.center_x - self.ids.main_image.norm_image_size[0] / 2.)
        print("\tAbsolute pos_y=", self.ids.main_image.center_y - self.ids.main_image.norm_image_size[1] / 2.)

示例

main.py

from kivy.uix.boxlayout import BoxLayout
from kivy.lang import Builder
from kivy.app import App
from kivy.uix.screenmanager import ScreenManager, Screen

Builder.load_string("""

<MyScreenManager>:
    ThirdScreen:
        id: third_screen

<ThirdScreen>:
    name: '_third_screen_'
    id: third_screen
    BoxLayout:
        orientation: "vertical"
        id: third_screen_boxlayout
        canvas:
        Label:
            id: main_title
            text: "Title"
            size_hint: (1, 0.1)
            canvas.before:
                Color:
                    rgba: 1, 0, 0, 1    # red
                Rectangle:
                    pos: self.pos
                    size: self.size
        Image:
            id: main_image
            # source: "C:/Users/OneDrive/0. T2/6. Kivy/4/claymore.jpg"
            source: "./claymore.jpeg"
            canvas.before:
                Color:
                    rgba: 0, 0, 1, 0.5    # blue
                Rectangle:
                    pos: self.pos
                    size: self.size
        BoxLayout:
            id: button_boxlayout
            orientation: "horizontal"
            padding: 10
            size_hint: (1, 0.15)
            Button:
                id: accept_button
                text: "Okay"
                size_hint: (0.33, 1)
                on_press: root.image_accepted_by_user(root.image_address)
            Button:
                id: crop_button
                text: "Crop"
                size_hint: (0.33, 1)
                on_press: root.enable_cropping()
            Button:
                id: cancel_button
                text: "Cancel"
                size_hint: (0.33, 1) 
                on_press: root.manager.current = '_first_screen_'
""")


class MyScreenManager(ScreenManager):
    pass


class ThirdScreen(Screen):
    def enable_cropping(self):
        print("\nThirdScreen:")
        print(self.ids.main_image.pos)
        print(self.ids.main_image.size)
        print("\tAbsolute size=", self.ids.main_image.norm_image_size)
        print("\tAbsolute pos_x=", self.ids.main_image.center_x - self.ids.main_image.norm_image_size[0] / 2.)
        print("\tAbsolute pos_y=", self.ids.main_image.center_y - self.ids.main_image.norm_image_size[1] / 2.)


class MyApp(App):
    def build(self):
        return MyScreenManager()


if __name__ == '__main__':
    MyApp().run()

输出