Source pixels.
Source x in the actual decoded buffer's pixel space.
Source y in that same space.
Interpolation kernel.
Destination RGBA buffer.
Byte offset of the destination pixel.
Output/source scale used for downsampling filter support; defaults to [1, 1].
Sample byte RGBA using GDAL-compatible kernels and write four channels into a caller-owned output buffer.
Source positions use pixel-corner coordinates:
[0.5, 0.5]is the first centre. Invalid/outside samples leave output unchanged, so initialize it transparent. GDAL notices and tested tolerances are in the package documentation.