Error

AssertionError: Images differ: maxDiff=0.942383 at position (0, 2); value=-0.464844 vs. 0.477539

Stacktrace

self = <test_fitsCompression.ImageCompressionTestCase testMethod=testQuantization>

    def testQuantization(self):

        """Test that our quantization produces the same values as cfitsio

            Our quantization is more configurable (e.g., choice of scaling algorithm,

            specifying mask planes) and extensible (logarithmic, asinh scalings)

            than cfitsio's. However, cfitsio uses its own fuzz ("subtractive dithering")

            when reading the data, so if we don't want to add random values twice,

            we need to be sure that we're using the same random values. To check that,

            we write one image with our scaling+compression, and one with cfitsio's

            compression using exactly the BSCALE and dither seed we used for our own.

            That way, the two codes will quantize independently, and we can compare

            the results.

            """

        bscaleSet = 1.0

        bzeroSet = self.background - 10*self.noise

        algorithm = ImageCompressionOptions.GZIP

        classList = (lsst.afw.image.ImageF, lsst.afw.image.ImageD)

        tilesList = ((4, 5), (0, 0), (0, 5), (4, 0), (0, 1))

        for cls, tiles in itertools.product(classList, tilesList):

            tiles = np.array(tiles, dtype=np.int64)

            compression = ImageCompressionOptions(algorithm, tiles, -bscaleSet)

            original = self.makeImage(cls)

            with lsst.utils.tests.getTempFilePath(self.extension) as filename:

                with lsst.afw.fits.Fits(filename, "w") as fits:

                    options = lsst.afw.fits.ImageWriteOptions(compression)

                    original.writeFits(fits, options)

                cfitsio = cls(filename)

                header = lsst.afw.image.readMetadata(filename, 1)

                seed = header.get("ZDITHER0")

                self.assertEqual(header.get("BSCALE"), bscaleSet)

            compression = ImageCompressionOptions(algorithm, tiles, 0.0)

            scaling = ImageScalingOptions(ImageScalingOptions.MANUAL, 32, [u"BAD"], bscale=bscaleSet,

                                          bzero=bzeroSet, fuzz=True, seed=seed)

            unpersisted = self.checkCompressedImage(cls, original, compression, scaling, atol=bscaleSet)

            oursDiff = unpersisted.getArray() - original.getArray()

            cfitsioDiff = cfitsio.getArray() - original.getArray()

>           self.assertImagesAlmostEqual(oursDiff, cfitsioDiff, atol=0.0)

tests/test_fitsCompression.py:720: 

_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 

python/lsst/afw/image/testUtils.py:118: in assertImagesAlmostEqual

    testCase.fail("%s: %s" % (msg, errStr))

E   AssertionError: Images differ: maxDiff=0.942383 at position (0, 2); value=-0.464844 vs. 0.477539

Standard Output

<class 'lsst.afw.image.image.image.ImageF'> CompressionAlgorithm.GZIP 8640 5760.0 1.5

Astropy currently doesn't read our compressed images perfectly.

<class 'lsst.afw.image.image.image.ImageF'> CompressionAlgorithm.GZIP 8640 5760.0 1.5

Astropy currently doesn't read our compressed images perfectly.

<class 'lsst.afw.image.image.image.ImageF'> CompressionAlgorithm.GZIP 8640 5760.0 1.5

Astropy currently doesn't read our compressed images perfectly.

<class 'lsst.afw.image.image.image.ImageF'> CompressionAlgorithm.GZIP 8640 5760.0 1.5

Astropy currently doesn't read our compressed images perfectly.

<class 'lsst.afw.image.image.image.ImageF'> CompressionAlgorithm.GZIP 8640 5760.0 1.5

Astropy currently doesn't read our compressed images perfectly.