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Support Y-channel PSNR and SSIM #250

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Apr 12, 2021
Merged

Support Y-channel PSNR and SSIM #250

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82082ed
Support Y-channel PSNR and SSIM
ckkelvinchan Apr 12, 2021
cf5a2db
fix bug
ckkelvinchan Apr 12, 2021
1dd1009
update naming and unittest
ckkelvinchan Apr 12, 2021
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30 changes: 28 additions & 2 deletions mmedit/core/evaluation/metrics.py
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Original file line number Diff line number Diff line change
Expand Up @@ -165,7 +165,7 @@ def reorder_image(img, input_order='HWC'):
return img


def psnr(img1, img2, crop_border=0, input_order='HWC'):
def psnr(img1, img2, crop_border=0, input_order='HWC', convert_to=None):
"""Calculate PSNR (Peak Signal-to-Noise Ratio).

Ref: https://en.wikipedia.org/wiki/Peak_signal-to-noise_ratio
Expand All @@ -177,6 +177,10 @@ def psnr(img1, img2, crop_border=0, input_order='HWC'):
pixels are not involved in the PSNR calculation. Default: 0.
input_order (str): Whether the input order is 'HWC' or 'CHW'.
Default: 'HWC'.
convert_to (str): Whether to convert the images to other color models.
If None, the images are not altered. When computing for 'Y',
the images are assumed to be in BGR order. Options are 'Y' and
None. Default: None.

Returns:
float: psnr result.
Expand All @@ -191,6 +195,14 @@ def psnr(img1, img2, crop_border=0, input_order='HWC'):
img1 = reorder_image(img1, input_order=input_order)
img2 = reorder_image(img2, input_order=input_order)

if isinstance(convert_to, str) and convert_to.lower() == 'y':
img1, img2 = img1.astype(np.float32), img2.astype(np.float32)
img1 = mmcv.bgr2ycbcr(img1 / 255., y_only=True) * 255.
img2 = mmcv.bgr2ycbcr(img2 / 255., y_only=True) * 255.
elif convert_to is not None:
raise ValueError(f'Wrong color model. Supported values are '
'"Y" and None.')

if crop_border != 0:
img1 = img1[crop_border:-crop_border, crop_border:-crop_border, None]
img2 = img2[crop_border:-crop_border, crop_border:-crop_border, None]
Expand Down Expand Up @@ -236,7 +248,7 @@ def _ssim(img1, img2):
return ssim_map.mean()


def ssim(img1, img2, crop_border=0, input_order='HWC'):
def ssim(img1, img2, crop_border=0, input_order='HWC', convert_to=None):
"""Calculate SSIM (structural similarity).

Ref:
Expand All @@ -255,6 +267,10 @@ def ssim(img1, img2, crop_border=0, input_order='HWC'):
pixels are not involved in the SSIM calculation. Default: 0.
input_order (str): Whether the input order is 'HWC' or 'CHW'.
Default: 'HWC'.
convert_to (str): Whether to convert the images to other color models.
If None, the images are not altered. When computing for 'Y',
the images are assumed to be in BGR order. Options are 'Y' and
None. Default: None.

Returns:
float: ssim result.
Expand All @@ -269,6 +285,16 @@ def ssim(img1, img2, crop_border=0, input_order='HWC'):
img1 = reorder_image(img1, input_order=input_order)
img2 = reorder_image(img2, input_order=input_order)

if isinstance(convert_to, str) and convert_to.lower() == 'y':
img1, img2 = img1.astype(np.float32), img2.astype(np.float32)
img1 = mmcv.bgr2ycbcr(img1 / 255., y_only=True) * 255.
img2 = mmcv.bgr2ycbcr(img2 / 255., y_only=True) * 255.
img1 = np.expand_dims(img1, axis=2)
img2 = np.expand_dims(img2, axis=2)
elif convert_to is not None:
raise ValueError(f'Wrong color model. Supported values are '
'"Y" and None')

if crop_border != 0:
img1 = img1[crop_border:-crop_border, crop_border:-crop_border, None]
img2 = img2[crop_border:-crop_border, crop_border:-crop_border, None]
Expand Down
16 changes: 16 additions & 0 deletions tests/test_metrics.py
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Original file line number Diff line number Diff line change
Expand Up @@ -36,6 +36,9 @@ def test_calculate_psnr():
with pytest.raises(ValueError):
psnr(img_hw_1, img_hw_2, crop_border=0, input_order='HH')

with pytest.raises(ValueError):
psnr(img_hw_1, img_hw_2, crop_border=0, convert_to='ABC')

psnr_result = psnr(img_hw_1, img_hw_2, crop_border=0)
np.testing.assert_almost_equal(psnr_result, 48.1308036)
psnr_result = psnr(img_hwc_1, img_hwc_2, crop_border=0, input_order='HWC')
Expand All @@ -50,6 +53,11 @@ def test_calculate_psnr():
psnr_result = psnr(img_chw_1, img_chw_2, crop_border=4, input_order='CHW')
np.testing.assert_almost_equal(psnr_result, 48.1308036)

psnr_result = psnr(img_hwc_1, img_hwc_2, crop_border=0, convert_to=None)
np.testing.assert_almost_equal(psnr_result, 48.1308036)
psnr_result = psnr(img_hwc_1, img_hwc_2, crop_border=0, convert_to='Y')
np.testing.assert_almost_equal(psnr_result, 49.4527218)

# test float inf
psnr_result = psnr(img_hw_1, img_hw_1, crop_border=0)
assert psnr_result == float('inf')
Expand All @@ -66,6 +74,9 @@ def test_calculate_ssim():
with pytest.raises(ValueError):
ssim(img_hw_1, img_hw_2, crop_border=0, input_order='HH')

with pytest.raises(ValueError):
ssim(img_hw_1, img_hw_2, crop_border=0, input_order='ABC')

ssim_result = ssim(img_hw_1, img_hw_2, crop_border=0)
np.testing.assert_almost_equal(ssim_result, 0.9130623)
ssim_result = ssim(img_hwc_1, img_hwc_2, crop_border=0, input_order='HWC')
Expand All @@ -80,6 +91,11 @@ def test_calculate_ssim():
ssim_result = ssim(img_chw_1, img_chw_2, crop_border=4, input_order='CHW')
np.testing.assert_almost_equal(ssim_result, 0.9130623)

ssim_result = ssim(img_hwc_1, img_hwc_2, crop_border=0, convert_to=None)
np.testing.assert_almost_equal(ssim_result, 0.9130623)
ssim_result = ssim(img_hwc_1, img_hwc_2, crop_border=0, convert_to='Y')
np.testing.assert_almost_equal(ssim_result, 0.9987801)


def test_calculate_niqe():
img = mmcv.imread('tests/data/gt/baboon.png')
Expand Down