5.3.8 Clipping and Masking Images
Level of expertise required for this Chapter: Advamced; general Map Maker training
Images can be too large (often, satellite images). It is then recommended to break it down into individual tile for easier and faster handling. You load only this one large image, which can take a long time, and define the frame:
1. Define a map frame
2. Calculate the frame (W, E, N, S)
3. Main menu > Utilities > Bitmap utilities > Mosaic and clip > Mosaic and clip calibrated bitmaps window: Add file (1, see below) > Select file type: JPG > Select folder and file > Open > and repeat for all files, you want to bring together > Define frame: Min X for west (2) > Min y for south > Max x for east > Max y for north > Check the red frame, which appears on the display > Check that Map Maker calibration is ticked (3) > OK (4) > Select file type: Recommended at LUPMIS is JPG > Specify new file name, preferably according to the map index > Save
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If the ‘frame’ can‘t be defined by coordinates (min and max x and y), but has an irregular shape, the masking tool can be applied.
Digitize the polygon of this irregular shape, which you want to ‘keep’, in Map Maker, and save it as a DRA file. All areas outside this polygon will not be copied to the new image.
In the Mosaic and clip calibrated bitmaps window, you don’t select ‘Add file’, but ‘Add file with mask’. After selecting the image (as explained above), you will be asked to enter the ‘mask’. All further processing will be the same.