diffvg/apps/test_eval_positions.py

import pydiffvg
import torch
import skimage
import numpy as np

# Use GPU if available
pydiffvg.set_use_gpu(torch.cuda.is_available())

canvas_width = 256
canvas_height = 256
circle = pydiffvg.Circle(radius = torch.tensor(40.0),
                         center = torch.tensor([128.0, 128.0]))
shapes = [circle]
circle_group = pydiffvg.ShapeGroup(shape_ids = torch.tensor([0]),
    fill_color = torch.tensor([0.3, 0.6, 0.3, 1.0]))
shape_groups = [circle_group]
scene_args = pydiffvg.RenderFunction.serialize_scene(\
    canvas_width, canvas_height, shapes, shape_groups,
    output_type = pydiffvg.OutputType.sdf)

render = pydiffvg.RenderFunction.apply
img = render(256, # width
             256, # height
             2,   # num_samples_x
             2,   # num_samples_y
             0,   # seed
             None, # background_image
             *scene_args)
img = img / 256 # Normalize SDF to [0, 1]
pydiffvg.imwrite(img.cpu(), 'results/test_eval_positions/target.png')
target = img.clone()

# Move the circle to produce initial guess
# normalize radius & center for easier learning rate
radius_n = torch.tensor(20.0 / 256.0, requires_grad=True)
center_n = torch.tensor([108.0 / 256.0, 138.0 / 256.0], requires_grad=True)
color = torch.tensor([0.3, 0.2, 0.8, 1.0], requires_grad=True)
circle.radius = radius_n * 256
circle.center = center_n * 256
circle_group.fill_color = color
scene_args = pydiffvg.RenderFunction.serialize_scene(\
    canvas_width, canvas_height, shapes, shape_groups,
    output_type = pydiffvg.OutputType.sdf)
img = render(256, # width
             256, # height
             2,   # num_samples_x
             2,   # num_samples_y
             1,   # seed
             None, # background_image
             *scene_args)
img = img / 256 # Normalize SDF to [0, 1]
pydiffvg.imwrite(img.cpu(), 'results/test_eval_positions/init.png')

# Optimize for radius & center
optimizer = torch.optim.Adam([radius_n, center_n, color], lr=1e-2)
# Run 200 Adam iterations.
for t in range(200):
    print('iteration:', t)
    optimizer.zero_grad()
    # Forward pass: render the image.
    circle.radius = radius_n * 256
    circle.center = center_n * 256
    circle_group.fill_color = color
    # Evaluate 1000 positions
    eval_positions = torch.rand(1000, 2).to(img.device) * 256
    # for grid_sample()
    grid_eval_positions = (eval_positions / 256.0) * 2.0 - 1.0
    scene_args = pydiffvg.RenderFunction.serialize_scene(\
        canvas_width, canvas_height, shapes, shape_groups,
        output_type = pydiffvg.OutputType.sdf,
        eval_positions = eval_positions)
    samples = render(256,   # width
                     256,   # height
                     0,     # num_samples_x
                     0,     # num_samples_y
                     t+1,   # seed
                     None, # background_image
                     *scene_args)
    samples = samples / 256 # Normalize SDF to [0, 1]
    target_sampled = torch.nn.functional.grid_sample(\
        target.view(1, 1, target.shape[0], target.shape[1]),
        grid_eval_positions.view(1, -1, 1, 2), mode='nearest')
    loss = (samples - target_sampled).pow(2).mean()
    print('loss:', loss.item())

    # Backpropagate the gradients.
    loss.backward()
    # Print the gradients
    print('radius.grad:', radius_n.grad)
    print('center.grad:', center_n.grad)
    print('color.grad:', color.grad)

    # Take a gradient descent step.
    optimizer.step()
    # Print the current params.
    print('radius:', circle.radius)
    print('center:', circle.center)
    print('color:', circle_group.fill_color)

# Render the final result.
scene_args = pydiffvg.RenderFunction.serialize_scene(\
    canvas_width, canvas_height, shapes, shape_groups,
    output_type = pydiffvg.OutputType.sdf)
img = render(256,   # width
             256,   # height
             2,     # num_samples_x
             2,     # num_samples_y
             102,    # seed
             None, # background_image
             *scene_args)
img = img / 256 # Normalize SDF to [0, 1]
# Save the images and differences.
pydiffvg.imwrite(img.cpu(), 'results/test_eval_positions/final.png')