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'''
This is an example of creating your own effect by writing a glsl string.
'''
from kivy.base import runTouchApp
from kivy.lang import Builder
from kivy.uix.effectwidget import EffectWidget, EffectBase
# The effect string is glsl code defining an effect function.
effect_string = '''
vec4 effect(vec4 color, sampler2D texture, vec2 tex_coords, vec2 coords)
{
// Note that time is a uniform variable that is automatically
// provided to all effects.
float red = color.x * abs(sin(time*2.0));
float green = color.y; // No change
float blue = color.z * (1.0 - abs(sin(time*2.0)));
return vec4(red, green, blue, color.w);
}
'''
class DemoEffect(EffectWidget):
def __init__(self, *args, **kwargs):
self.effect_reference = EffectBase(glsl=effect_string)
super(DemoEffect, self).__init__(*args, **kwargs)
widget = Builder.load_string('''
DemoEffect:
effects: [self.effect_reference] if checkbox.active else []
orientation: 'vertical'
Button:
text: 'Some text so you can see what happens.'
BoxLayout:
size_hint_y: None
height: dp(50)
Label:
text: 'Enable effect?'
CheckBox:
id: checkbox
active: True
''')
runTouchApp(widget)
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