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Preserve the channel axis in HSL conversions #125

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Preserve the channel axis in HSL conversions #125

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9 changes: 6 additions & 3 deletions dm_pix/_src/color_conversion.py
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Original file line number Diff line number Diff line change
Expand Up @@ -212,7 +212,7 @@ def rgb_to_hsl(
(2 * eps + jnp.where(c_sum <= 1, c_sum, 2 - c_sum)))
l = c_sum / 2

return jnp.stack([h, s, l], axis=-1)
return jnp.stack([h, s, l], axis=channel_axis)


def hsl_to_rgb(
Expand Down Expand Up @@ -246,8 +246,11 @@ def _f(hue):
hue < 0.5, m2,
jnp.where(hue < 2 / 3, m1 + 6 * (m2 - m1) * (2 / 3 - hue), m1)))

image_rgb = jnp.stack([_f(h + 1 / 3), _f(h), _f(h - 1 / 3)], axis=-1)
return jnp.where(s[..., jnp.newaxis] == 0, l[..., jnp.newaxis], image_rgb) # pyrefly: ignore[bad-index]
image_rgb = jnp.stack(
[_f(h + 1 / 3), _f(h), _f(h - 1 / 3)], axis=channel_axis)
return jnp.where(
jnp.expand_dims(s == 0, axis=channel_axis),
jnp.expand_dims(l, axis=channel_axis), image_rgb)


def rgb_to_grayscale(
Expand Down
28 changes: 28 additions & 0 deletions dm_pix/_src/color_conversion_test.py
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Original file line number Diff line number Diff line change
Expand Up @@ -233,6 +233,34 @@ def test_hsl_to_rgb_golden(self):
np.testing.assert_allclose(
hsl_to_rgb(image_hsl), rgb_true, atol=1E-5, rtol=1E-5)

@parameterized.product(
conversion=('rgb_to_hsl', 'hsl_to_rgb'),
channel_axis=(0, 1, -2, -1),
batched=(False, True),
use_jit=(False, True),
)
def test_hsl_channel_axis(self, conversion, channel_axis, batched, use_jit):
rgb = np.array([
[[0., 0., 0.], [1., 1., 1.], [0.5, 0.5, 0.5], [1., 0., 0.]],
[[0., 1., 0.], [0., 0., 1.], [0.2, 0.4, 0.7], [0.8, 0.3, 0.1]],
], dtype=np.float32)
if batched:
rgb = np.stack([rgb, rgb[::-1]])
hsl = []
for pixel in rgb.reshape(-1, 3):
h, l, s = colorsys.rgb_to_hls(*map(float, pixel))
hsl.append([h, s, l])
hsl = np.asarray(hsl, dtype=np.float32).reshape(rgb.shape)
image, expected = (rgb, hsl) if conversion == 'rgb_to_hsl' else (hsl, rgb)
image = jnp.asarray(np.moveaxis(image, -1, channel_axis))
expected = np.moveaxis(expected, -1, channel_axis)
convert = functools.partial(
getattr(color_conversion, conversion), channel_axis=channel_axis)
actual = (jax.jit(convert) if use_jit else convert)(image)
self.assertEqual(actual.shape, image.shape)
self.assertEqual(actual.dtype, image.dtype)
np.testing.assert_allclose(actual, expected, atol=1e-6, rtol=1e-6)

@chex.all_variants
def test_hsl_rgb_roundtrip(self):
key = jax.random.PRNGKey(0)
Expand Down
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