René's URL Explorer Experiment

{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"Issues with `imshow` and  RGBA values","articleBody":"Raised at https://stackoverflow.com/questions/25089068/how-does-imshow-handle-the-alpha-channel-with-an-m-x-n-x-4-input  by @mwaskom\n\n```\nimport numpy as np\nimport matplotlib.pyplot as plt\n\nd = np.ones((100, 100, 4), dtype=np.uint8)*255\nd[:, :, 3] = np.linspace(0, 255, num=100)\nplt.imshow(d, interpolation='none')\nplt.show()\n```\n\nOne might expect the image to be completely white (as semi-transparent white over white should still be white), but is instead gray in the middle due to pre-multiplying of the alpha (1, 1, 1, .5) -\u003e (.5, .5, .5) which is then composited with the background as an opaque layer, hence the gray.\n\nPreviously (related) discussion:\n- https://www.mail-archive.com/matplotlib-users@lists.sourceforge.net/msg22377.html\n- PR #545\n","author":{"url":"https://github.com/tacaswell","@type":"Person","name":"tacaswell"},"datePublished":"2014-08-04T23:16:17.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":8},"url":"https://github.com/3343/matplotlib/issues/3343"}