Pyglet draw text into texture

Question

I'm trying to render an image with OpenGL using Pyglet. So far I've been able to setup the framebuffer and texture, render into it and save it as a PNG image. But I can't find out how to use Pyglets font rendering.

import numpy as np
import pyglet
from pyglet.gl import *
from ctypes import byref, sizeof, POINTER

width = 800
height = 600
cpp = 4

# Create the framebuffer (rendering target).
buf = gl.GLuint(0)
glGenFramebuffers(1, byref(buf))
glBindFramebuffer(GL_FRAMEBUFFER, buf)

# Create the texture (internal pixel data for the framebuffer).
tex = gl.GLuint(0)
glGenTextures(1, byref(tex))
glBindTexture(GL_TEXTURE_2D, tex)
glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, width, height, 0, GL_RGBA, GL_FLOAT, None)

# Bind the texture to the framebuffer.
glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_2D, tex, 0)

# Something may have gone wrong during the process, depending on the
# capabilities of the GPU.
res = glCheckFramebufferStatus(GL_FRAMEBUFFER)
if res != GL_FRAMEBUFFER_COMPLETE:
  raise RuntimeError('Framebuffer not completed')

glViewport(0, 0, width, height)

# DRAW BEGIN
# =====================
glClearColor(0.1, 0.1, 0.1, 1.0)
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glColor3f(1.0, 0.5, 0.02)
glRectf(-0.75, -0.75, 0.75, 0.75)

glColor3f(1.0, 1.0, 1.0)
label = pyglet.text.Label(
  "Hello, World", font_name='Times New Roman', font_size=36,
  x=0, y=0, anchor_x='center', anchor_y='center')
label.draw()
# =====================
# DRAW END

# Read the buffer contents into a numpy array.
data = np.empty((height, width, cpp), dtype=np.float32)
glReadPixels(0, 0, width, height, GL_RGBA, GL_FLOAT, data.ctypes.data_as(POINTER(GLfloat)))

# Save the image.
import imageio
data = np.uint8(data * 255)
imageio.imwrite("foo.png", data)

The text does not appear on the framebuffer. How can I render the label on the framebuffer?

Answer 1

For rendering labels in Pyglet, first, an orthographic projection should be set up. In the given example, do it as follows:

glMatrixMode(GL_PROJECTION)
glLoadIdentity()
glOrtho(0, width, 0, height, -1, 1)
glMatrixMode(GL_MODELVIEW)
glLoadIdentity()
glColor3f(1.0, 1.0, 1.0)
label = pyglet.text.Label(
  "Hello, World", font_name='Times New Roman', font_size=36,
  x=width/2, y=height/2, anchor_x='center', anchor_y='center')
label.draw()

Then, the label is rendered as expected. (Note: moved the label's offset to the image center, ie x=width/2, y=height/2, )

foo.png (output framebuffer image)