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{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"Inconsistency with behavior of extent and origin in imshow()","articleBody":"Following a brief discussion on Gitter, I've decided to open an issue here but I'm not 100% sure if this is a bug or intended behavior. The following script compares the usage of origin and extent when the limits are fixed to the same intervals and same axis direction:\r\n\r\n```python\r\nimport numpy as np\r\nimport matplotlib.pyplot as plt\r\n\r\nimage = np.arange(100).reshape((10, 10))\r\n\r\nsubplot = 0\r\n\r\nfig = plt.figure(figsize=(8, 8))\r\n\r\nfor extent in [None, [1, 9, 1, 9]]:\r\n    for origin in ['lower', 'upper']:\r\n        subplot += 1\r\n        ax = fig.add_subplot(2, 2, subplot)\r\n        ax.imshow(image, interpolation='nearest', origin=origin,\r\n                  extent=extent)\r\n        ax.set_xlim(0, 10)\r\n        ax.set_ylim(0, 10)\r\n        ax.set_title('extent={0} origin={1}'.format(extent, origin),\r\n                     fontsize=8)\r\n\r\nfig.savefig('thumbs.png')\r\n```\r\n\r\nThe output is:\r\n\r\n![thumbs](https://cloud.githubusercontent.com/assets/314716/26653549/54905a3c-464b-11e7-910f-c375faf36ead.png)\r\n\r\nAs you can see, when no extent is specified, the origin keyword has no impact on the result whereas it does when the extent is specified.\r\n\r\nThere is either a bug here, or something that exists for historical reasons that deserves its own documentation section.\r\n\r\nIn any case, the documentation for ``origin`` doesn't make much sense:\r\n\r\n```\r\norigin : ['upper' | 'lower'], optional, default: None\r\n    Place the [0,0] index of the array in the upper left or lower left\r\n    corner of the axes. If None, default to rc `image.origin`.\r\n```\r\n\r\nthe concept of 'upper left' or 'lower left' is tricky since the axes can be made to go in either direction, so whether [0,0] is at the upper or lower corner visually depends on the direction of the axes.\r\n\r\nIt seems that when extent is not specified, origin simply means that the y limits are flipped but this can be reverted by setting ylim. When extent is present, the array is truly flipped vertically.\r\n\r\ncc @tacaswell @ngoldbaum @WeatherGod \r\n\r\n","author":{"url":"https://github.com/astrofrog","@type":"Person","name":"astrofrog"},"datePublished":"2017-05-31T20:55:27.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":9},"url":"https://github.com/8693/matplotlib/issues/8693"}