signals.py

from vispy import gloo
from vispy import app
import numpy as np
import math

m = 20
n = 25000
x = np.tile(np.linspace(-1., 1., n), m)
y = .1 * np.random.randn(m, n)
y += np.arange(m).reshape((-1, 1))

data = np.zeros(n*m, dtype=[
    ('a_position', np.float32, 2),
    ('a_color', np.float32, 3),
    ('a_index', np.float32, 1),
])

data['a_position'] = np.zeros((n*m, 2), dtype=np.float32)
data['a_position'][:,0] = x
data['a_position'][:,1] = .9*(y.ravel()/y.max()*2-1)

data['a_color'] = np.repeat(np.random.uniform(size=(m, 3), low=.5, high=.9), n, axis=0)

data['a_index'] = np.repeat(np.arange(m), n)

VERT_SHADER = """
#version 120
attribute vec2 a_position;
attribute float a_index;
varying float v_index;

attribute vec3 a_color;
varying vec3 v_color;

uniform vec2 u_pan;
uniform vec2 u_scale;

void main() {
    
    vec2 position_tr = u_scale * (a_position + u_pan);
    gl_Position = vec4(position_tr, 0.0, 1.0);
    v_color = a_color;
    v_index = a_index;
}
"""

FRAG_SHADER = """
#version 120
varying vec3 v_color;
varying float v_index;
void main() {
    gl_FragColor = vec4(v_color, 1.0);
    if ((fract(v_index) > .00001) && (fract(v_index) < .99999))
        gl_FragColor.a = 0.;
}
"""

class Canvas(app.Canvas):
    def __init__(self):
        app.Canvas.__init__(self, close_keys='escape')
        self.program = gloo.Program(VERT_SHADER, FRAG_SHADER)
        self.program.bind(gloo.VertexBuffer(data))
        
        self.program['u_pan'] = (0., 0.)
        self.program['u_scale'] = (1., 1.)

    def on_initialize(self, event):
        gloo.set_state(clear_color=(1, 1, 1, 1), blend=True, 
                       blend_func=('src_alpha', 'one_minus_src_alpha'))

    def on_resize(self, event):
        self.width, self.height = event.size
        gloo.set_viewport(0, 0, self.width, self.height)

    def on_draw(self, event):
        gloo.clear(color=(0.0, 0.0, 0.0, 1.0))
        self.program.draw('line_strip')

    def on_mouse_move(self, event):
        
        def _normalize((x, y)):
            w, h = float(self.width), float(self.height)
            return x/(w/2.)-1., y/(h/2.)-1.
            
        if event.is_dragging:
            x0, y0 = _normalize(event.press_event.pos)
            x1, y1 = _normalize(event.last_event.pos)
            x, y = _normalize(event.pos)
            dx, dy = x - x1, -(y - y1)
            button = event.press_event.button
            
            pan_x, pan_y = self.program['u_pan']
            scale_x, scale_y = self.program['u_scale']
            
            if button == 1:
                self.program['u_pan'] = (pan_x+dx/scale_x, pan_y+dy/scale_y)
            elif button == 2:
                scale_x_new, scale_y_new = scale_x * math.exp(2.5*dx), scale_y * math.exp(2.5*dy)
                self.program['u_scale'] = (scale_x_new, scale_y_new)
                self.program['u_pan'] = (pan_x - x0 * (1./scale_x - 1./scale_x_new), 
                                         pan_y + y0 * (1./scale_y - 1./scale_y_new))
            self.update()
        
c = Canvas()
c.show()
app.run()