Operating system: Linux-3.10.0-693.21.1.el7.x86_64-x86_64-with-centos-7.4.1708-Core 64 Bits
Graphics card: Quadro M5000/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 396.54
Broken: version: 2.82 (sub 1), branch: master, commit date: 2019-10-24 19:11, hash: rB2a3b5dc73038
Short description of error
Grease pencil has weird edges when put over a Camera Background Image (it doesnt happen over an image texture)
Exact steps for others to reproduce the error
Create a new 2D animation file
drag and drop an image to the viewport to get it as a background image
draw on top of it.
see the white borders around the drawing?, its much worse when the strenght of the pencil is driven by pressure or when the strength is not 100 percent.
here are some samples