cv - Find contours in image (:cv_find_shapes)

Declaration

found_shapes, visualized = img:cv_find_shapes(shapes[, options])

Parameters

• shapes
  Table. One or more shapes' vertex info to search for

  Shapes parameter structure

  {
      { -- shape 1
          { -- vertex 1
              ["y"] = number_value,
              ["x"] = number_value,
          },
          { -- vertex 2
              ["y"] = number_value,
              ["x"] = number_value,
          },
          ...
      },
      { -- shape 2
          { -- vertex 1
              ["y"] = number_value,
              ["x"] = number_value,
          },
          { -- vertex 2
              ["y"] = number_value,
              ["x"] = number_value,
          },
          ...
      },
      ...
  }

• options
  Table, optional. Contour matching options

  Option fields

  {
      should_visualize = false | true,  -- optional, whether to output visualization, default false
      closed = false | true,            -- optional, whether shapes are closed, default false
      min_area = number_value,          -- optional, minimum area, default -1 (no limit)
      max_area = number_value,          -- optional, maximum area, default -1 (no limit)
      blur_size = integer_value,        -- optional, blur kernel size, positive odd number only, default 3
      canny_threshold1 = 100,           -- optional, Canny lower threshold, default 100
      canny_threshold2 = 200,           -- optional, Canny upper threshold, default 200
      diff_threshold = number_value,    -- optional, difference threshold, smaller means more similar, default 0.001
      approx_epsilon = integer_value,   -- optional, contour approximation percentage of perimeter, default 2
  }

Returns

• found_shapes
  Table

  Found shapes structure

  {
      { -- list of shapes matching input shape 1
          {
              diff_score = number_value, -- smaller is more similar
              { -- vertex 1
                  ["y"] = number_value,
                  ["x"] = number_value,
              },
              { -- vertex 2
                  ["y"] = number_value,
                  ["x"] = number_value,
              },
              ...
          },
          { -- second match for input shape 1
              diff_score = number_value,
              { -- vertex 1
                  ["y"] = number_value,
                  ["x"] = number_value,
              },
              { -- vertex 2
                  ["y"] = number_value,
                  ["x"] = number_value,
              },
              ...
          },
          ...
      },
      { -- list of shapes matching input shape 2
          { -- first match
              diff_score = number_value,
              { -- vertex 1
                  ["y"] = number_value,
                  ["x"] = number_value,
              },
              { -- vertex 2
                  ["y"] = number_value,
                  ["x"] = number_value,
              },
              ...
          },
          { -- second match
              diff_score = number_value,
              { -- vertex 1
                  ["y"] = number_value,
                  ["x"] = number_value,
              },
              { -- vertex 2
                  ["y"] = number_value,
                  ["x"] = number_value,
              },
              ...
          },
          ...
      },
      ...
  }

• visualized
  Image object. When options.should_visualize is true, this is the visualization image

Description

Find one or more shapes from an image
Standard regular shapes can be generated by functions

Example

function make_triangle(side_len)
    local hf = math.sqrt(3)/2
    local h = math.floor(hf * side_len)
    return {
        { ["x"] = 1, ["y"] = h },
        { ["x"] = side_len, ["y"] = h },
        { ["x"] = side_len // 2, ["y"] = 1 },
    }
end

function make_rectangle(side_len)
    return {
        { ["x"] = 1, ["y"] = 1 },
        { ["x"] = 1, ["y"] = side_len },
        { ["x"] = side_len, ["y"] = side_len },
        { ["x"] = side_len, ["y"] = 1 },
    }
end

local info, visimg = screen.image():cv_find_shapes({make_triangle(45), make_rectangle(40)}, {
    min_area = 2000,
    max_area = 20000,
    diff_threshold = 0.005,
    approx_epsilon = 1,
    shape_match_mode = 3,
    closed = true,
    should_visualize = true,
})

nLog(info[1])
nLog(info[2])

dialog():add_image(visimg):show()