René's URL Explorer Experiment

{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"[Doc]: documentation of how to properly rasterize output of contourf","articleBody":"### Documentation Link\n\nhttps://matplotlib.org/stable/gallery/images_contours_and_fields/contourf_demo.html\n\n### Problem\n\nThe contourf demo could use a clear example of how to properly rasterize the output.   It may be useful to include this information directly in the contourf documentation.  \r\n\r\nHere's a minimal example that shows what used to work for me (based on the example in the [contourf demo](https://matplotlib.org/stable/gallery/images_contours_and_fields/contourf_demo.html) and the top answer from [stackoverflow](https://stackoverflow.com/questions/47698830/rasterization-of-contours-in-filled-contour-plot)), but is now deprecated as of matplotlib 3.8:\r\n\r\n```\r\nimport numpy as np\r\nimport matplotlib.pyplot as plt\r\ndelta = 0.025\r\n\r\nx = y = np.arange(-3.0, 3.01, delta)\r\nX, Y = np.meshgrid(x, y)\r\nZ1 = np.exp(-X**2 - Y**2)\r\nZ2 = np.exp(-(X - 1)**2 - (Y - 1)**2)\r\nZ = (Z1 - Z2) * 2\r\n\r\nfig, ax = plt.subplots()\r\n\r\ncont = ax.contourf(X,Y,Z, levels = 100)\r\n\r\nfor c in cont.collections:\r\n    c.set_rasterized(True)\r\n```\r\nThis now returns:\r\n```\r\nMatplotlibDeprecationWarning: The collections attribute was deprecated in Matplotlib 3.8 and will be removed two minor releases later.\r\n  for c in cont.collections:\r\n```\r\n\r\nIt's not obvious to me how I should be rasterizing a contourf for matplotlib\u003e=3.8 (regardless of whether the method I used above was sensical or not...at least it worked).\r\n\r\nIf I try to apply something similar to what is in the current [rasterization demo](https://matplotlib.org/stable/gallery/misc/rasterization_demo.html),  (which I think resulted from https://github.com/matplotlib/matplotlib/issues/17708/ ),\r\n```\r\nfig2, ax2 = plt.subplots()\r\ncont = ax2.contourf(X,Y,Z, levels = 100, rasterized=True)\r\n```\r\nthen I get the following error:\r\n```\r\nUserWarning: The following kwargs were not used by contour: 'rasterized'\r\n  cont = ax2.contourf(X,Y,Z, levels = 100, rasterized=True)\r\n```\r\n\r\n\n\n### Suggested improvement\n\n1. Include a paragraph and code snippet somewhere in https://matplotlib.org/stable/gallery/images_contours_and_fields/contourf_demo.html explaining how to rasterize contourf.  \r\n\r\n2. maybe include a description of how to rasterize directly in the documentation of contourf","author":{"url":"https://github.com/tarrla","@type":"Person","name":"tarrla"},"datePublished":"2024-01-18T23:25:55.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":3},"url":"https://github.com/27669/matplotlib/issues/27669"}