kivy Line with gradient color

[Degenerate Tech]

i have Line i want ro fill its texture with gradient color . how to do ?

[elli...@cox.net]

If you are creating a simple horizontal or vertical line, you could create a narrow rectangle and set the texture to be a gradient.

See: https://github.com/kengoon/KivyGradient

GitHub - kengoon/KivyGradient Contribute to kengoon/KivyGradient development by creating an account on GitHub. github.com

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Sent: Sunday, May 12, 2024 2:19 AM
To: Kivy users support <kivy-...@googlegroups.com>
Subject: [kivy-users] kivy Line with gradient color

 

i have Line i want ro fill its texture with gradient color . how to do ?

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[Degenerate Tech]

How to curve it. I want lines so I can it circle or other lines types

[elli...@cox.net]

Looking at the docs it appears that all of the drawing instructions can take a texture, so I created a small experiment.

I copied the core of the KivyGradient code ( it is just 2 methods) and drew a random line with a texture.  One strange effect, the texture needed to be updated or the line turns white.  I bound to the Window draw... This feels hacky.  It might be worth copying the gradient to a file,  and trying the source attribute.

Anyway - here is the code.

from kivy.app import App

from kivy.lang import Builder

from kivy.uix.widget import Widget

from kivy.graphics.texture import Texture

from kivy.properties import ObjectProperty

from kivy.utils import colormap, get_random_color

from kivy.clock import Clock

from kivy.core.window import Window

from itertools import chain

kv = """

<GradientWidget>:

    canvas:

        Line:

            width: 2

            points: [100, 100, 600, 100, 100, 200, 300, 500]  # just some random points

            texture: self.gradient

BoxLayout:

    GradientWidget:

        id: gw

"""

class Gradient:

    """

    From: https://github.com/kengoon/KivyGradient

    """

    @staticmethod

    def horizontal(*args):

        """

        Create a horizontal gradient

        :param args: colors that will make up the gradient in order

        :return: A Texture of the desired gradient

        """

        texture = Texture.create(size=(len(args), 1), colorfmt='rgba')

        buf = bytes([int(v * 255) for v in chain(*args)])  # flattens

        texture.blit_buffer(buf, colorfmt='rgba', bufferfmt='ubyte')

        return texture

    @staticmethod

    def vertical(*args):

        """

        Create a Vertical gradient

        :param args: colors that will make up the gradient in order

        :return: A Texture of the desired gradient

        """

        texture = Texture.create(size=(1, len(args)), colorfmt='rgba')

        buf = bytes([int(v * 255) for v in chain(*args)])  # flattens

        texture.blit_buffer(buf, colorfmt='rgba', bufferfmt='ubyte')

        return texture

class GradientWidget(Widget):

    gradient = ObjectProperty()

    def set_gradient(self, *args):

        try:

            colors = [colormap[arg] for arg in args]

            self.gradient = Gradient.horizontal(*colors)

        except KeyError:

            print('KeyError: invalid color used')

class GradientExperiment(App):

    def build(self):

        Window.bind(on_draw=self.win_update)  # need to update texture on redraw?

        return Builder.load_string(kv)

    def set_colors(self):

        self.root.ids.gw.set_gradient('red', 'yellow', 'green', 'lightgreen', 'lightblue',

                                      'darkblue', 'violet')

    def set_random_colors(self, dt):

        self.root.ids.gw.gradient = Gradient.horizontal(*[get_random_color() for _ in range(5)])

    def win_update(self, *args):

        self.set_colors()

GradientExperiment().run()

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From: kivy-...@googlegroups.com <kivy-...@googlegroups.com> on behalf of Degenerate Tech <sksah...@gmail.com>

Sent: Monday, May 13, 2024 12:56 AM

To: Kivy users support <kivy-...@googlegroups.com>

Subject: Re: [kivy-users] kivy Line with gradient color

 

To view this discussion on the web visit https://groups.google.com/d/msgid/kivy-users/52842654-d24c-4d87-bcb6-cadf9b42fdd3n%40googlegroups.com.

[Degenerate Tech]

Yeah . Great . Same thing I was thinking. Line also take texture 👍👍👍👍👍

[Degenerate Tech]

see in this code gradient textture is not loading . please see or where i am wrong ?

[ELLIOT GARBUS]

I suspect you are seeing the same issue I saw, note in my code that I am updating the texture on each redraw by binding to the Window on_draw event. 

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Sent: Sunday, May 26, 2024 6:37 AM

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[ELLIOT GARBUS]

Looking at the documentation, I found the answer:  https://kivy.org/doc/stable/api-kivy.graphics.texture.html#reloading-the-texture

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From: ELLIOT GARBUS <elli...@cox.net>
Sent: Sunday, May 26, 2024 9:02 AM

[ElliotG]

I updated my earlier experiment... I was not able to get the reload_observer to operate ( This was a surprise).  I just do not understand OGL well enough I suppose.  

This still feels like a hack - but it is better.

from kivy.app import App
from kivy.lang import Builder
from kivy.uix.widget import Widget
from kivy.graphics.texture import Texture

from kivy.utils import colormap
from kivy.graphics import Line
from kivy.clock import Clock

from itertools import chain


kv = """

BoxLayout:
    GradientWidget:
        id: gw
"""


class GradientWidget(Widget):

    def __init__(self, **kwargs):
        super().__init__(**kwargs)
        self.texture = None
        self.buf = None

    def horizontal(self, *args):

        """
        Create a horizontal gradient
        :param args: colors that will make up the gradient in order

        :return: None
        From: https://github.com/kengoon/KivyGradient
        """
        self.texture = Texture.create(size=(len(args), 1), colorfmt='rgba')
        # self.texture.add_reload_observer(self.rlo)  # not tiggered?
        self.buf = bytes([int(v * 255) for v in chain(*args)])  # flattens
        Clock.schedule_interval(self.update, 0)

    def rlo(self):
        print('rlo')  # Never called... ???

    def update(self, *args):
        print('update')
        self.texture.blit_buffer(self.buf, colorfmt='rgba', bufferfmt='ubyte')
        with self.canvas:
            Line(width=2, points=[100, 100, 600, 100, 100, 200, 300, 500], texture=self.texture)

    def set_gradient(self, *args):
        print('set gradient')

        try:
            colors = [colormap[arg] for arg in args]

            self.horizontal(*colors)

        except KeyError:
            print('KeyError: invalid color used')


class GradientExperiment(App):
    def build(self):

        return Builder.load_string(kv)

    def set_colors(self):
        self.root.ids.gw.set_gradient('red', 'yellow', 'green', 'lightgreen', 'lightblue',
                                      'darkblue', 'violet')

    def on_start(self):
        self.set_colors()


GradientExperiment().run()