Kristin Cowalcijk created SEDONA-477:
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Summary: Avoid producing rasters with images having non-zero
origins
Key: SEDONA-477
URL: https://issues.apache.org/jira/browse/SEDONA-477
Project: Apache Sedona
Issue Type: Bug
Reporter: Kristin Cowalcijk
Fix For: 1.6.0
Attachments: Untitled Diagram.drawio (1).png
{{RS_Clip}} may produce GridCoverage2D objects containing a PlanarImage with
non-zero origin. AWT allows images to have a non-zero origin, and {{RS_Clip}}
apply a mosaic operation on the original image to cut off its visible area. The
pixel coordinates of the visible area remain unchanged, only the valid ranges
of pixel coordinates were changed. The ranges of valid pixel coordinates are
represented by the minX, minY, width, and height properties of the AWT image.
AWT images with non-zero origins bring a full range of problems when handling
such GridCoverage2D objects, because lots of band operation code assumes that
the images have zero origin, and the BufferedImage of AWT also does not allow
images with non-zero origin, which makes it difficult to construct image
objects from in-memory buffer.
We decided to make all GridCoverage2D objects have zero origin, rather than
fixing all band operation routines to make them handle non-zero origins
correctly since this is very difficult. We defined a helper function
RasterUtils.shiftRasterToZeroOrigin to shift the raster with non-zero origin to
have zero origin, and shift the affine transformation to cancel with the origin
shift, thus keeping the actual grid coverage unchanged. Please refer to the
attached figure for how it works.
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