Volume Freehand Cropping ======================== Algorithm to interactively remove/cut parts of a volume using a freeform selection directly in the views. Input ----- A single 3D volume. Output ------ A new 3D volume with the freehand cropping applied or nothing if **Create new image** or **Apply as mask** is disabled. Description ----------- The Volume Freehand Cropping algorithm enables you to interactively remove parts from a 3D volume. Similar to image editing software you can draw freehand selections in any of the views showing the input data and thereby define which voxels are to be removed. During editing, the views will show a live preview: all voxels that are going to be removed are tinted in red. Once you click on **Apply** the previewed changes are applied and the final result is computed. .. image:: ../img/VolumeFreehandCropping.png You can define the removed region interactively in multiple steps by drawing a freehand region in any of the views showing the input data. This will accumulate mask overlay indicating which pixels should be removed (tinted in red) and which pixels should be kept alive. Depending on the chosen Interaction mode the drawing of the freehand region has different effects on the masked region: - **Draw:** all voxels that are inside the region when projected onto the view plane will be added to the masked region. - **Intersect:** all voxels that are inside the region when projected onto the view plane **and** are already part of the mask will remain part of the mask. All other voxels will be removed from the mask. - **Erase:** all voxels that are inside the region when projected onto the view plane will be removed from the mask. - **Invert:** invert the mask image swapping regions that should be removed with regions that should be kept alive. - **Clear:** clear the mask so that no pixels are considered as removed anymore. You can further configure the following options: - Check **Create new image** in order to keep the input image unchanged and create a new image as output with the result. The output image will have all masked pixels set to 0. - Check **Apply as mask** in order to keep the input image pixel values as they are but attach an explicit mask with the previously defined regions. See also the :ref:`Edit Mask Algorithm`. - Check **Fit volume to crop** in order to reduce the volume size to tightly fit the cropped region.