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en:processing:анализ_выделенных_областей [2012/02/07 15:01] Анна Протопопова |
en:processing:анализ_выделенных_областей [2012/03/14 15:19] |
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| - | ===== Selected area analysis===== | ||
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| - | This function from the [[en:processing:меню_математика|Mathematics menu]] is oriented to determination of surface area and volume in selected region of the image. | ||
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| - | To start working with this function one should select an area of interest with [[en:processing:выделение|standard selection tools]]: selection of rectangular areas, selection of ellipses, or selection of isolines. The latter is often preferable. When the selection is ready call the **Selected area analysis** function. A new parameters window will apear it will be refilled after every future call to the function. Thereby one can prepare a table of parameters during his work with different areas and images. When the table is ready one can copy the data to Excel or to any other programm for statistical analysis. | ||
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| - | {{:processing:selected_area_analysis_2.jpg|An AFM image of mica surface with three protein spheres on it}} | ||
| - | {{:processing:selected_area_analysis_1.jpg|The table of parameters}} | ||
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| - | Let's understand how the parameters are calculated, starting with the objects surface area. | ||
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| - | An algorithm of surface area determination is based on triangulate meshwork constitution. The surface area is defined as a sum of triangles in selection: | ||
| - | * every 4 neighboring pixels of the image are combined in the unit cell used in the construction of a triangulated mesh, | ||
| - | * a new point located on the medium height is added at the center of every unit cell, | ||
| - | * thus four triangles are formed with one common apex at the center of the square and the other two at the sites of the unit cell, | ||
| - | * surface area is calculated as the sum of the areas of triangles, as shown in a Figure: | ||
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| - | {{:processing:триангуляция.jpg?200|}} | ||
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| - | The surface area is written into the second column of the parameters table **//S_full//**. | ||