Cutting Images
The data model of image type is directly responsible for the physical size of database occupying the biggest store areas. It is worth to remember determined operations on the images uses huge computer efforts.
To minimize this problem user can do a layer cut of image type thus excluding image regions that are not part of the study area.
This operational is very useful in many situations such as, reduce a physical size of database, creation of smaller images to perform tests, image split in specific areas (city perimeter, chart sheets, etc.) and generation of new images to printing layouts.
To do cuts, the user should define the limit of interest. This limit can be defined in three modes:
Vector: from a vectorial theme, that contains polygon type geometries. (Possibility to use all geometries in the layer or only selected ones by pointing).
Block: from definition of width and height of blocks
Region of Interest: from drawn polygons in the visualization area.
The result is a new layer of image type or a geotiff file
Select IMAGE PROCESSING → FUNCTIONS → RASTER CUT in the main menu. Raster Cut window opens.
Input Theme: choose from the theme list the target image.
Cut by: Select the parameter to be used to cut: vector, block or ROI.
Vectorial Theme: if vector is selected, enter the value from the scroll bar.
Group by Attribute: if selected select the attribute from the list.
Use selected geometries by pointing: select this option if you want to choose the geometries.
Width block, height block: if block is selected enter the values for block width and height.
Acquire: if ROI is selected click on the Acquire button to define regions. ROI window opens.
Click
on the icon
for rectangle selection of area,
for polygon selection of area, or
for magic wand selection of area.
Slide button or type the number of ?????
Visual Transparency: ?????
Slide button or type the value of transparency percentage.???
Click in OK button.
Back to Raster Cut window continue configuring output parameters.
Select Geo Tiff if image will be saved in a file. Select Layer if image is to be stored in the database.
Select Generate as Unique Image if only unique image is to be generated including all cuts. Otherwise, it will be generated new images depending on the number of cuts.
Select Generate Multi Resolution and enter the number of levels.
Base Name: Enter the theme name or the file name of cut image.