Selecting the overlapping tiles: Multiple ways to do this, but one is: Use a FeatureReader to read the "selection polygon". Send it to another FeatureReader to read the grid, set Spatial Filter to "Initiator Intersects Result". You could also use a SpatialFilter to do this.
Copying the overlapping rasters: Also multiple ways to do this. I would use a FeatureReader with the "Directory and File Pathnames" format to scan the folder with rasters. Then use a FeatureMerger to merge the result of the previous action to the features. Merged is inside the "selection polygon". Then use a FeatureWriter with the "File Copy" format to copy the images to a new location. As an alternative you can use a SystemCaller to do it like you would do commandline.
Merging the rasters: Read the rasters. If not georeferenced, use a RasterGeoreferencer to put the rasters on coordinates. Then use a RasterMosaiker to merge them into one. FeatureWriter to write the result.
- Use a small dataset when developing the workspace to keep the iteration time low. Rasters can be time and memory consuming.
- Baby steps. Add a Transformer, run the workspace. When it works, next step. If it does not, tinker on. Otherwise it is hard to isolate the issue.
Update 201907310646: Added a printscreen of a raw workflow to clarify. As I have no data I can't work it out in more detail. If you supply a sample set I can.
My assumption is you have the following inputs:
- A shapefile with a selection polygon.
- A shapefile with the grid of the images, which has unique filenames corresponding with the rasterfiles.
- A set of rasterfiles. (If not georeferenced, some steps need to be added.)
Supply feedback if my assumptions are wrong or if this doesn't work out for you.