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copied!<p>It looks like there are some bugs with converting to/from numpy with the <code>1</code> mode.</p> <p>If you convert it to <code>L</code> first, it works fine:</p> <pre><code>>>> im <BmpImagePlugin.BmpImageFile image mode=1 size=2x2 at 0x17F17E8> >>> im2 = im.convert('L') >>> numpy.asarray(im2) array([[ 0, 255], [255, 0]], dtype=uint8) </code></pre> <p>Also, if you try and convert a <code>bool</code> numpy array to PIL, you get strange results:</p> <pre><code>>>> testarr = numpy.array([[True,False],[True,False]], dtype=numpy.bool) >>> testpil = Image.fromarray(testarr, mode='1') >>> numpy.asarray(testpil) array([[False, False], [False, False]], dtype=bool) </code></pre> <p>However, the exact same thing with <code>uint8</code> works fine:</p> <pre><code>>>> testarr = numpy.array([[255,0],[0,255]], dtype=numpy.uint8) >>> Image.fromarray(testarr) <Image.Image image mode=L size=2x2 at 0x1B51320> >>> numpy.asarray(Image.fromarray(testarr)) array([[255, 0], [ 0, 255]], dtype=uint8) </code></pre> <p>So I would suggest using <code>L</code> as an intermediate datatype and then converting to <code>1</code> before saving if you need to save it in that format. Something like this:</p> <pre><code>>>> im <BmpImagePlugin.BmpImageFile image mode=1 size=2x2 at 0x17F17E8> >>> im2 = im.convert('L') >>> arr = numpy.asarray(im2) >>> arr array([[ 0, 255], [255, 0]], dtype=uint8) >>> arr = arr == 255 >>> arr array([[False, True], [ True, False]], dtype=bool) </code></pre> <p>Then to convert back:</p> <pre><code>>>> backarr = numpy.zeros(arr.shape, dtype=numpy.uint8) >>> backarr[arr] = 255 >>> backarr array([[ 0, 255], [255, 0]], dtype=uint8) >>> Image.fromarray(backarr).convert('1') <Image.Image image mode=1 size=2x2 at 0x1B41CB0> </code></pre>

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