test_crop.py

'''Demonstrate showing a cropped image using get_region

Drop any image supported by kivy on the window and play with the sliders
'''
from kivy.app import App
from kivy.lang import Builder
from kivy.core.window import Window
from kivy import properties as P


KV = '''
BoxLayout:
    orientation: 'vertical'
    Label:
        text: 'drop an image file on the window and play with the sliders'
        size_hint_y: None
        height: self.texture_size[1]
        font_size: dp(25)
        text_size: self.width, None

    BoxLayout:
        Image:
            id: full_image
            source: app.source
        Image:
            crop_rect: crop_left.value, crop_bottom.value, crop_width.value, crop_height.value
            crop_rect:
            texture:
                full_image.texture.get_region(
                (full_image.texture_size[0] * crop_left.value),
                (full_image.texture_size[1] * crop_bottom.value),
                (full_image.texture_size[0] * (crop_left.value + crop_width.value)),
                (full_image.texture_size[1] * (crop_bottom.value + crop_height.value)),
                ) if full_image.texture else None

    GridLayout:
        cols: 2
        Label:
            text: 'crop left'
        Slider:
            id: crop_left
            min: 0
            max: 1
            value: 1

        Label:
            text: 'crop bottom'
        Slider:
            id: crop_bottom
            min: 0
            max: 1
            value: 1

        Label:
            text: 'crop width'
        Slider:
            id: crop_width
            min: .0001
            max: 1
            value: 1

        Label:
            text: 'crop height'
        Slider:
            id: crop_height
            min: .0001
            max: 1
            value: 1
'''  # noqa


class Application(App):
    source = P.StringProperty()

    def build(self):
        Window.bind(on_dropfile=self.update_source)
        return Builder.load_string(KV)

    def update_source(self, window, path):
        try:
            self.source = path.decode('utf8')
        except Exception as exception:
            print(exception)
            self.source = ''


if __name__ == "__main__":
    Application().run()