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Fix #152455: OpenEXR DWAA/DWAB saving leads to inf values

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DWAA/DWAB lossy compression uses DCT-based encoding, where values near
HALF_MAX can overshoot to infinity after decompression, due to DCT ringing.

There are different ways to resolves it and it's not so clear what the ideal
solution would be and how it would be handled upstream. By default it
will already convert values > HALF_MAX to inf and it's up to the application
to clamp if they want to (like we do).

As a workaround, clamp half float values before writing with an empirically
determined value that takes into account that lower quality makes this
problem worse. The resulting files should then decompress without inf in
existing software.

Pull Request: https://projects.blender.org/blender/blender/pulls/154061
This commit is contained in:
Brecht Van Lommel 2026-01-31 12:44:56 +01:00 • committed by Gitea
parent c17eb901f7
commit fac8b300e0
15 changed files with 78 additions and 14 deletions
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15
tests/python/bl_imbuf_save.py
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@ -18,6 +18,7 @@ args = None
TEMPLATE_RGBA08 = "template-rgba08.png"
TEMPLATE_RGBA32 = "template-rgba32.exr"
TEMPLATE_HIGH_VALUES = "extreme_values/template-high-values.exr"
class ImBufTest(AbstractImBufTest):
@ -31,7 +32,7 @@ class ImBufTest(AbstractImBufTest):
def _load_template_image(self, name, template_name):
image_path = str(self.test_dir.joinpath(template_name))
bpy.ops.image.open(filepath=image_path)
img = bpy.data.images[template_name]
img = bpy.data.images[pathlib.Path(template_name).name]
img.name = name
return img
@ -47,7 +48,7 @@ class ImBufTest(AbstractImBufTest):
name += str(settings[s]).rjust(2, '0') + "-"
# do not embed exr quality into test file name unless it is DWAA/DWAB
elif not (s == "quality" and ext == "exr" and
settings.get("exr_codec") not in ("DWAA", "DWAB")):
settings.get("exr_codec") not in ("DWAA", "DWAB")):
name += str(settings[s]) + "-"
setattr(image_settings, s, settings[s])
@ -60,6 +61,7 @@ class ImBufTest(AbstractImBufTest):
loaders = {
"rgba08": lambda name: self._load_template_image(name, TEMPLATE_RGBA08),
"rgba32": lambda name: self._load_template_image(name, TEMPLATE_RGBA32),
"high-values": lambda name: self._load_template_image(name, TEMPLATE_HIGH_VALUES),
}
# Load the template image and assign it the image name
@ -144,6 +146,15 @@ class ImBufSaveTest(ImBufTest):
self.check(src="rgba32", ext="exr", settings={"file_format": "OPEN_EXR", "color_mode": "RGB", "color_depth": "16", "exr_codec": "HTJ2K"})
self.check(src="rgba32", ext="exr", settings={"file_format": "OPEN_EXR", "color_mode": "RGBA", "color_depth": "32", "exr_codec": "HTJ2K"})
def test_save_exr_dwa_high_values(self):
self.skip_if_format_missing("OPENEXR")
# Tests for correct clamping of values that exceed HALF_MAX.
self.check(src="high-values", ext="exr", settings={"file_format": "OPEN_EXR", "color_mode": "RGB", "color_depth": "16", "exr_codec": "DWAA", "quality": 100})
self.check(src="high-values", ext="exr", settings={"file_format": "OPEN_EXR", "color_mode": "RGB", "color_depth": "16", "exr_codec": "DWAA", "quality": 90})
self.check(src="high-values", ext="exr", settings={"file_format": "OPEN_EXR", "color_mode": "RGB", "color_depth": "16", "exr_codec": "DWAA", "quality": 75})
self.check(src="high-values", ext="exr", settings={"file_format": "OPEN_EXR", "color_mode": "RGB", "color_depth": "16", "exr_codec": "DWAA", "quality": 50})
def test_save_hdr(self):
self.check(src="rgba08", ext="hdr", settings={"file_format": "HDR", "color_mode": "BW"})
self.check(src="rgba08", ext="hdr", settings={"file_format": "HDR", "color_mode": "RGB"})