{
  "__type": "IngestedDoc",
  "__tag": 4010,
  "_content": {
    "Notes": {
      "__type": "Section",
      "__tag": 4015,
      "children": [
        {
          "__type": "Paragraph",
          "__tag": 4045,
          "children": [
            {
              "__type": "Text",
              "__tag": 4046,
              "value": "If "
            },
            {
              "__type": "ParamRef",
              "__tag": 4071,
              "name": "data_range"
            },
            {
              "__type": "Text",
              "__tag": 4046,
              "value": " is not specified, the range is automatically guessed based on the image data type. However for floating-point image data, this estimate yields a result double the value of the desired range, as the "
            },
            {
              "__type": "InlineRole",
              "__tag": 4003,
              "value": "dtype_range",
              "domain": null,
              "role": null,
              "inventory": null
            },
            {
              "__type": "Text",
              "__tag": 4046,
              "value": " in "
            },
            {
              "__type": "InlineRole",
              "__tag": 4003,
              "value": "skimage.util.dtype.py",
              "domain": null,
              "role": null,
              "inventory": null
            },
            {
              "__type": "Text",
              "__tag": 4046,
              "value": " has defined intervals from -1 to +1. This yields an estimate of 2, instead of 1, which is most often required when working with image data (as negative light intensities are nonsensical). In case of working with YCbCr-like color data, note that these ranges are different per channel (Cb and Cr have double the range of Y), so one cannot calculate a channel-averaged SSIM with a single call to this function, as identical ranges are assumed for each channel."
            }
          ]
        },
        {
          "__type": "Paragraph",
          "__tag": 4045,
          "children": [
            {
              "__type": "Text",
              "__tag": 4046,
              "value": "To match the implementation of Wang et al. "
            },
            {
              "__type": "FootnoteReference",
              "__tag": 4066,
              "label": "1"
            },
            {
              "__type": "Text",
              "__tag": 4046,
              "value": ", set "
            },
            {
              "__type": "ParamRef",
              "__tag": 4071,
              "name": "gaussian_weights"
            },
            {
              "__type": "Text",
              "__tag": 4046,
              "value": " to True, "
            },
            {
              "__type": "CrossRef",
              "__tag": 4002,
              "value": "sigma",
              "reference": {
                "__type": "RefInfo",
                "__tag": 4000,
                "module": null,
                "version": null,
                "kind": "local",
                "path": "sigma"
              },
              "kind": "local"
            },
            {
              "__type": "Text",
              "__tag": 4046,
              "value": " to 1.5, "
            },
            {
              "__type": "CrossRef",
              "__tag": 4002,
              "value": "use_sample_covariance",
              "reference": {
                "__type": "RefInfo",
                "__tag": 4000,
                "module": null,
                "version": null,
                "kind": "local",
                "path": "use_sample_covariance"
              },
              "kind": "local"
            },
            {
              "__type": "Text",
              "__tag": 4046,
              "value": " to False, and specify the "
            },
            {
              "__type": "ParamRef",
              "__tag": 4071,
              "name": "data_range"
            },
            {
              "__type": "Text",
              "__tag": 4046,
              "value": " argument."
            }
          ]
        },
        {
          "__type": "Admonition",
          "__tag": 4056,
          "kind": "versionchanged",
          "base_type": "neutral",
          "children": [
            {
              "__type": "AdmonitionTitle",
              "__tag": 4055,
              "children": [
                {
                  "__type": "Text",
                  "__tag": 4046,
                  "value": "versionchanged 0.16"
                }
              ]
            },
            {
              "__type": "Paragraph",
              "__tag": 4045,
              "children": [
                {
                  "__type": "Text",
                  "__tag": 4046,
                  "value": "This function was renamed from "
                },
                {
                  "__type": "InlineCode",
                  "__tag": 4051,
                  "value": "skimage.measure.compare_ssim"
                },
                {
                  "__type": "Text",
                  "__tag": 4046,
                  "value": " to "
                },
                {
                  "__type": "InlineCode",
                  "__tag": 4051,
                  "value": "skimage.metrics.structural_similarity"
                },
                {
                  "__type": "Text",
                  "__tag": 4046,
                  "value": "."
                }
              ]
            }
          ]
        }
      ],
      "title": [],
      "level": 0,
      "target": null
    },
    "Warns": {
      "__type": "Section",
      "__tag": 4015,
      "children": [],
      "title": [],
      "level": 0,
      "target": null
    },
    "Raises": {
      "__type": "Section",
      "__tag": 4015,
      "children": [],
      "title": [],
      "level": 0,
      "target": null
    },
    "Yields": {
      "__type": "Section",
      "__tag": 4015,
      "children": [],
      "title": [],
      "level": 0,
      "target": null
    },
    "Methods": {
      "__type": "Section",
      "__tag": 4015,
      "children": [],
      "title": [],
      "level": 0,
      "target": null
    },
    "Returns": {
      "__type": "Section",
      "__tag": 4015,
      "children": [
        {
          "__type": "Parameters",
          "__tag": 4026,
          "children": [
            {
              "__type": "DocParam",
              "__tag": 4016,
              "name": "mssim",
              "annotation": "float",
              "desc": [
                {
                  "__type": "Paragraph",
                  "__tag": 4045,
                  "children": [
                    {
                      "__type": "Text",
                      "__tag": 4046,
                      "value": "The mean structural similarity index over the image."
                    }
                  ]
                }
              ]
            },
            {
              "__type": "DocParam",
              "__tag": 4016,
              "name": "grad",
              "annotation": "ndarray",
              "desc": [
                {
                  "__type": "Paragraph",
                  "__tag": 4045,
                  "children": [
                    {
                      "__type": "Text",
                      "__tag": 4046,
                      "value": "The gradient of the structural similarity between im1 and im2 "
                    },
                    {
                      "__type": "FootnoteReference",
                      "__tag": 4066,
                      "label": "2"
                    },
                    {
                      "__type": "Text",
                      "__tag": 4046,
                      "value": ". This is only returned if "
                    },
                    {
                      "__type": "ParamRef",
                      "__tag": 4071,
                      "name": "gradient"
                    },
                    {
                      "__type": "Text",
                      "__tag": 4046,
                      "value": " is set to True."
                    }
                  ]
                }
              ]
            },
            {
              "__type": "DocParam",
              "__tag": 4016,
              "name": "S",
              "annotation": "ndarray",
              "desc": [
                {
                  "__type": "Paragraph",
                  "__tag": 4045,
                  "children": [
                    {
                      "__type": "Text",
                      "__tag": 4046,
                      "value": "The full SSIM image.  This is only returned if "
                    },
                    {
                      "__type": "ParamRef",
                      "__tag": 4071,
                      "name": "full"
                    },
                    {
                      "__type": "Text",
                      "__tag": 4046,
                      "value": " is set to True."
                    }
                  ]
                }
              ]
            }
          ]
        }
      ],
      "title": [],
      "level": 0,
      "target": null
    },
    "Summary": {
      "__type": "Section",
      "__tag": 4015,
      "children": [
        {
          "__type": "Paragraph",
          "__tag": 4045,
          "children": [
            {
              "__type": "Text",
              "__tag": 4046,
              "value": "Compute the mean structural similarity index between two images. Please pay attention to the "
            },
            {
              "__type": "ParamRef",
              "__tag": 4071,
              "name": "data_range"
            },
            {
              "__type": "Text",
              "__tag": 4046,
              "value": " parameter with floating-point images."
            }
          ]
        }
      ],
      "title": [],
      "level": 0,
      "target": null
    },
    "Receives": {
      "__type": "Section",
      "__tag": 4015,
      "children": [],
      "title": [],
      "level": 0,
      "target": null
    },
    "Warnings": {
      "__type": "Section",
      "__tag": 4015,
      "children": [],
      "title": [],
      "level": 0,
      "target": null
    },
    "Attributes": {
      "__type": "Section",
      "__tag": 4015,
      "children": [],
      "title": [],
      "level": 0,
      "target": null
    },
    "Parameters": {
      "__type": "Section",
      "__tag": 4015,
      "children": [
        {
          "__type": "Parameters",
          "__tag": 4026,
          "children": [
            {
              "__type": "DocParam",
              "__tag": 4016,
              "name": "im1, im2",
              "annotation": "ndarray",
              "desc": [
                {
                  "__type": "Paragraph",
                  "__tag": 4045,
                  "children": [
                    {
                      "__type": "Text",
                      "__tag": 4046,
                      "value": "Images. Any dimensionality with same shape."
                    }
                  ]
                }
              ]
            },
            {
              "__type": "DocParam",
              "__tag": 4016,
              "name": "win_size",
              "annotation": "int or None, optional",
              "desc": [
                {
                  "__type": "Paragraph",
                  "__tag": 4045,
                  "children": [
                    {
                      "__type": "Text",
                      "__tag": 4046,
                      "value": "The side-length of the sliding window used in comparisons (default: 7). Must be an odd value. If "
                    },
                    {
                      "__type": "ParamRef",
                      "__tag": 4071,
                      "name": "gaussian_weights"
                    },
                    {
                      "__type": "Text",
                      "__tag": 4046,
                      "value": " is True, "
                    },
                    {
                      "__type": "ParamRef",
                      "__tag": 4071,
                      "name": "win_size"
                    },
                    {
                      "__type": "Text",
                      "__tag": 4046,
                      "value": " cannot be specified since the window size is determined by "
                    },
                    {
                      "__type": "CrossRef",
                      "__tag": 4002,
                      "value": "sigma",
                      "reference": {
                        "__type": "RefInfo",
                        "__tag": 4000,
                        "module": null,
                        "version": null,
                        "kind": "local",
                        "path": "sigma"
                      },
                      "kind": "local"
                    },
                    {
                      "__type": "Text",
                      "__tag": 4046,
                      "value": "."
                    }
                  ]
                }
              ]
            },
            {
              "__type": "DocParam",
              "__tag": 4016,
              "name": "gradient",
              "annotation": "bool, optional",
              "desc": [
                {
                  "__type": "Paragraph",
                  "__tag": 4045,
                  "children": [
                    {
                      "__type": "Text",
                      "__tag": 4046,
                      "value": "If True, also return the gradient with respect to im2."
                    }
                  ]
                }
              ]
            },
            {
              "__type": "DocParam",
              "__tag": 4016,
              "name": "data_range",
              "annotation": "float, optional",
              "desc": [
                {
                  "__type": "Paragraph",
                  "__tag": 4045,
                  "children": [
                    {
                      "__type": "Text",
                      "__tag": 4046,
                      "value": "The data range of the input image (difference between maximum and minimum possible values). By default, this is estimated from the image data type. This estimate may be wrong for floating-point image data. Therefore it is recommended to always pass this scalar value explicitly (see note below)."
                    }
                  ]
                }
              ]
            },
            {
              "__type": "DocParam",
              "__tag": 4016,
              "name": "channel_axis",
              "annotation": "int or None, optional",
              "desc": [
                {
                  "__type": "Paragraph",
                  "__tag": 4045,
                  "children": [
                    {
                      "__type": "Text",
                      "__tag": 4046,
                      "value": "If None, the image is assumed to be a grayscale (single channel) image. Otherwise, this parameter indicates which axis of the array corresponds to channels."
                    }
                  ]
                },
                {
                  "__type": "Admonition",
                  "__tag": 4056,
                  "kind": "versionadded",
                  "base_type": "neutral",
                  "children": [
                    {
                      "__type": "AdmonitionTitle",
                      "__tag": 4055,
                      "children": [
                        {
                          "__type": "Text",
                          "__tag": 4046,
                          "value": "versionadded 0.19"
                        }
                      ]
                    },
                    {
                      "__type": "Paragraph",
                      "__tag": 4045,
                      "children": [
                        {
                          "__type": "InlineCode",
                          "__tag": 4051,
                          "value": "channel_axis"
                        },
                        {
                          "__type": "Text",
                          "__tag": 4046,
                          "value": " was added in 0.19."
                        }
                      ]
                    }
                  ]
                }
              ]
            },
            {
              "__type": "DocParam",
              "__tag": 4016,
              "name": "gaussian_weights",
              "annotation": "bool, optional",
              "desc": [
                {
                  "__type": "Paragraph",
                  "__tag": 4045,
                  "children": [
                    {
                      "__type": "Text",
                      "__tag": 4046,
                      "value": "If True, the local mean and variance are computed using a normalized Gaussian kernel of width "
                    },
                    {
                      "__type": "CrossRef",
                      "__tag": 4002,
                      "value": "sigma",
                      "reference": {
                        "__type": "RefInfo",
                        "__tag": 4000,
                        "module": null,
                        "version": null,
                        "kind": "local",
                        "path": "sigma"
                      },
                      "kind": "local"
                    },
                    {
                      "__type": "Text",
                      "__tag": 4046,
                      "value": " rather than a uniform window."
                    }
                  ]
                }
              ]
            },
            {
              "__type": "DocParam",
              "__tag": 4016,
              "name": "full",
              "annotation": "bool, optional",
              "desc": [
                {
                  "__type": "Paragraph",
                  "__tag": 4045,
                  "children": [
                    {
                      "__type": "Text",
                      "__tag": 4046,
                      "value": "If True, also return the full structural similarity image."
                    }
                  ]
                }
              ]
            }
          ]
        }
      ],
      "title": [],
      "level": 0,
      "target": null
    },
    "Extended Summary": {
      "__type": "Section",
      "__tag": 4015,
      "children": [],
      "title": [],
      "level": 0,
      "target": null
    },
    "Other Parameters": {
      "__type": "Section",
      "__tag": 4015,
      "children": [
        {
          "__type": "Parameters",
          "__tag": 4026,
          "children": [
            {
              "__type": "DocParam",
              "__tag": 4016,
              "name": "use_sample_covariance",
              "annotation": "bool",
              "desc": [
                {
                  "__type": "Paragraph",
                  "__tag": 4045,
                  "children": [
                    {
                      "__type": "Text",
                      "__tag": 4046,
                      "value": "If True, normalize covariances by N-1 rather than, N where N is the number of pixels within the sliding window."
                    }
                  ]
                }
              ]
            },
            {
              "__type": "DocParam",
              "__tag": 4016,
              "name": "K1",
              "annotation": "float",
              "desc": [
                {
                  "__type": "Paragraph",
                  "__tag": 4045,
                  "children": [
                    {
                      "__type": "Text",
                      "__tag": 4046,
                      "value": "Algorithm parameter, K1 (small constant, see "
                    },
                    {
                      "__type": "FootnoteReference",
                      "__tag": 4066,
                      "label": "1"
                    },
                    {
                      "__type": "Text",
                      "__tag": 4046,
                      "value": ")."
                    }
                  ]
                }
              ]
            },
            {
              "__type": "DocParam",
              "__tag": 4016,
              "name": "K2",
              "annotation": "float",
              "desc": [
                {
                  "__type": "Paragraph",
                  "__tag": 4045,
                  "children": [
                    {
                      "__type": "Text",
                      "__tag": 4046,
                      "value": "Algorithm parameter, K2 (small constant, see "
                    },
                    {
                      "__type": "FootnoteReference",
                      "__tag": 4066,
                      "label": "1"
                    },
                    {
                      "__type": "Text",
                      "__tag": 4046,
                      "value": ")."
                    }
                  ]
                }
              ]
            },
            {
              "__type": "DocParam",
              "__tag": 4016,
              "name": "sigma",
              "annotation": "float",
              "desc": [
                {
                  "__type": "Paragraph",
                  "__tag": 4045,
                  "children": [
                    {
                      "__type": "Text",
                      "__tag": 4046,
                      "value": "Standard deviation for the Gaussian when "
                    },
                    {
                      "__type": "ParamRef",
                      "__tag": 4071,
                      "name": "gaussian_weights"
                    },
                    {
                      "__type": "Text",
                      "__tag": 4046,
                      "value": " is True. Default is 1.5."
                    }
                  ]
                }
              ]
            }
          ]
        }
      ],
      "title": [],
      "level": 0,
      "target": null
    }
  },
  "_ordered_sections": [
    "Summary",
    "Extended Summary",
    "Parameters",
    "Returns",
    "Yields",
    "Receives",
    "Raises",
    "Warns",
    "Other Parameters",
    "Attributes",
    "Methods",
    "Notes",
    "Warnings"
  ],
  "item_file": "/dev/scikit-image/src/skimage/metrics/_structural_similarity.py",
  "item_line": 13,
  "item_type": "function",
  "aliases": [
    "skimage.metrics.structural_similarity"
  ],
  "example_section_data": {
    "__type": "Section",
    "__tag": 4015,
    "children": [],
    "title": [],
    "level": 0,
    "target": null
  },
  "see_also": [],
  "signature": {
    "__type": "SignatureNode",
    "__tag": 4029,
    "kind": "function",
    "parameters": [
      {
        "__type": "SigParam",
        "__tag": 4030,
        "name": "im1",
        "annotation": {
          "__type": "Empty",
          "__tag": 4031
        },
        "kind": "POSITIONAL_OR_KEYWORD",
        "default": {
          "__type": "Empty",
          "__tag": 4031
        }
      },
      {
        "__type": "SigParam",
        "__tag": 4030,
        "name": "im2",
        "annotation": {
          "__type": "Empty",
          "__tag": 4031
        },
        "kind": "POSITIONAL_OR_KEYWORD",
        "default": {
          "__type": "Empty",
          "__tag": 4031
        }
      },
      {
        "__type": "SigParam",
        "__tag": 4030,
        "name": "win_size",
        "annotation": {
          "__type": "Empty",
          "__tag": 4031
        },
        "kind": "KEYWORD_ONLY",
        "default": "None"
      },
      {
        "__type": "SigParam",
        "__tag": 4030,
        "name": "gradient",
        "annotation": {
          "__type": "Empty",
          "__tag": 4031
        },
        "kind": "KEYWORD_ONLY",
        "default": "False"
      },
      {
        "__type": "SigParam",
        "__tag": 4030,
        "name": "data_range",
        "annotation": {
          "__type": "Empty",
          "__tag": 4031
        },
        "kind": "KEYWORD_ONLY",
        "default": "None"
      },
      {
        "__type": "SigParam",
        "__tag": 4030,
        "name": "channel_axis",
        "annotation": {
          "__type": "Empty",
          "__tag": 4031
        },
        "kind": "KEYWORD_ONLY",
        "default": "None"
      },
      {
        "__type": "SigParam",
        "__tag": 4030,
        "name": "gaussian_weights",
        "annotation": {
          "__type": "Empty",
          "__tag": 4031
        },
        "kind": "KEYWORD_ONLY",
        "default": "False"
      },
      {
        "__type": "SigParam",
        "__tag": 4030,
        "name": "full",
        "annotation": {
          "__type": "Empty",
          "__tag": 4031
        },
        "kind": "KEYWORD_ONLY",
        "default": "False"
      },
      {
        "__type": "SigParam",
        "__tag": 4030,
        "name": "kwargs",
        "annotation": {
          "__type": "Empty",
          "__tag": 4031
        },
        "kind": "VAR_KEYWORD",
        "default": {
          "__type": "Empty",
          "__tag": 4031
        }
      }
    ],
    "return_annotation": {
      "__type": "Empty",
      "__tag": 4031
    },
    "target_name": "structural_similarity"
  },
  "references": [
    ".. [1] Wang, Z., Bovik, A. C., Sheikh, H. R., & Simoncelli, E. P.",
    "   (2004). Image quality assessment: From error visibility to",
    "   structural similarity. IEEE Transactions on Image Processing,",
    "   13, 600-612.",
    "   https://ece.uwaterloo.ca/~z70wang/publications/ssim.pdf,",
    "   :DOI:`10.1109/TIP.2003.819861`",
    "",
    ".. [2] Avanaki, A. N. (2009). Exact global histogram specification",
    "   optimized for structural similarity. Optical Review, 16, 613-621.",
    "   :arxiv:`0901.0065`",
    "   :DOI:`10.1007/s10043-009-0119-z`"
  ],
  "qa": "skimage.metrics._structural_similarity:structural_similarity",
  "arbitrary": [],
  "local_refs": [
    "K1",
    "K2",
    "S",
    "channel_axis",
    "data_range",
    "full",
    "gaussian_weights",
    "grad",
    "gradient",
    "im1",
    "im2",
    "mssim",
    "sigma",
    "use_sample_covariance",
    "win_size"
  ]
}