# Working with a Region In some cases, most often to decrease the processing time or to single-out the object you want to analyze, you do not want to process the whole image but only a part of it. You can define and use regions of interest (ROI) to restrict the area processed with your vision tool. * In **eVision:** * An **ROI** [`EBaseROI`](../../doxygen_cpp/classeVision_1_1EBaseROI.html) [.NET](../../doxygen_cs/classeVision_1_1EBaseROI.html) [Python](../../doxygen_python/classeVision_1_1EBaseROI.html) class designates a rectangular region of interest. * A **region** [`ERegion`](../../doxygen_cpp/classeVision_1_1ERegion.html) [.NET](../../doxygen_cs/classeVision_1_1ERegion.html) [Python](../../doxygen_python/classeVision_1_1ERegion.html) class designates an arbitrarily shaped ROI. With regions, you can determine precisely which part of the image, down to a single pixel, is used for your processing. #### SEE ALSO For more details on ERegions, see [**Arbitrarily Shaped ROI (ERegion)**](../../using/basic_operations/regions/arbitrarily_shaped_roi__eregion_.html.md). #### HINT An ERegion is an arbitrary shape. If you want to use a simple rectangular ROI attached to an image, consider [**Step 3: Managing an ROI:**](running_tools_on_images/index.html.md#managing-an-roi). ## Process ### 1. Draw the ERegion Though it is not required, it is often easier to draw the ERegion based on an actual image: * Add an image tool. * Open an image representative of your setup. #### SEE ALSO See [**Step 1: Creating a Graph:**](running_tools_on_images/index.html.md#creating-a-graph). ### 2. Add a `Region Editor` Tool: ![image](assets/images/easy_studio2_common/working_with_a_region_1.webp) * The `Region editor` tool is added to the graph. ### 3. Connect the Source Image: * This is only required if you are using an image as input to help drawing the region. * Connect the `Image file` tool to the `Region editor` tool and select a `Link type` for this connection. ### 4. Draw your Region: ![](assets/images/easy_studio2_common/working_with_a_region_2.webp) * Use add `Primitives` buttons and, using your mouse, move and adjust the shapes. * SHIFT + click to select 2 shapes in the list. * Click on a button (merge, intersection or substract) to combine them. * Select it in the list, set the Radius and click on the `Grow region` or `Shrink region` button. * Either in the same project or a different one. * `Save` it first. * Then `Load` it. #### HINT Don’t forget to link the tool by connecting your `Region editor` output `region` port to the input `region` port of another tool.