Vispy heatmap

heatmap.py

import numpy as np
from vispy import app, gloo


vertex = """
uniform vec4 viewport;
attribute vec2 position;
attribute vec2 texcoord;
varying vec2 v_texcoord;
varying vec2 v_pixcoord;
varying vec2 v_quadsize;
void main()
{
    gl_Position = vec4(position,0.0,1.0);
    v_texcoord = texcoord;
    v_quadsize = viewport.zw;
    v_pixcoord = texcoord * v_quadsize;
}
"""

fragment = """
uniform sampler2D texture;
varying vec2 v_texcoord;
varying vec2 v_quadsize;
varying vec2 v_pixcoord;
vec4 filled(float distance, float linewidth, float antialias, vec4 fill)
{
    vec4 frag_color;
    float t = linewidth/2.0 - antialias;
    float signed_distance = distance;
    float border_distance = abs(signed_distance) - t;
    float alpha = border_distance/antialias;
    alpha = exp(-alpha*alpha);
    if( border_distance < 0.0 )
        frag_color = fill;
    else if( signed_distance < 0.0 )
        frag_color = fill;
    else
        frag_color = vec4(fill.rgb, alpha * fill.a);
    return frag_color;
}
float marker(vec2 P, float size)
{
    return max(abs(P.x), abs(P.y)) - size/2.0;
}
void main()
{
    const float rows = 50.0;
    const float cols = 50.0;
    float v = texture2D(texture, v_texcoord).r;
    vec2 size = v_quadsize / vec2(cols,rows);
    vec2 center = (floor(v_pixcoord/size) + vec2(0.5,0.5)) * size;
    float d = marker(v_pixcoord - center, 0.9*size.x);
    gl_FragColor = filled(d, 1.0, 1.0, vec4(v,v,v,1));
}
"""

c = app.Canvas(keys='interactive', size=(600, 600))

program = gloo.Program(vertex, fragment)
program['position'] = np.array([(-1,-1), (-1,1), (1,-1), (1,1)],
                               dtype=np.float32)
program['texcoord'] = np.array([( 0, 1), ( 0, 0), ( 1, 1), ( 1, 0)],
                               dtype=np.float32)
program['texture'] = np.random.uniform(0,1,(50,50)).astype(np.float32)

@c.connect
def on_draw(ev):
    gloo.clear('white')
    program.draw("triangle_strip")

@c.connect
def on_resize(ev):
    width, height = ev.size
    program['viewport'] = 0, 0, width, height

c.show()
app.run()

Do you know how I can add color this, and also set a 1:1 aspect ratio?

Took me a while, but I figured it out...

Replace

width, height = ev.size
program['viewport'] = 0, 0, width, height

with ' gloo.set_viewport` and some fixed size, like

gloo.set_viewport(0, 0, 1000, 1000)

This last line of code can also be placed under def on_draw(ev):

Phew!

Vispy is a remarkable piece of software, but, even assuming proficiency in GLSL, it's non-obvious how vispy interfaces with gloo/OpenGL.... @rossant Do you know of any Vispy tutorials other than your (pretty good) IPython Cookbook one? There's a ton of material on GLSL and OpenGL ES 2.0, but I'm desperately looking for more material on the vispy API other than the official documentation (which is not the most verbose, if you don't mind me saying) and the source itself.