Imagine an image of 140x139 (this one : )
If you import in blender with images as plane addon, with emission or shadeless shader
And set your render output to the same resolution and framerate
And add an orthographic camera above to the center of your image, with orthographic view
You can adjust the size by zooming a lot in a corner from the camera view ...
The problem is that a backup copy of your donut and icing are still rendered. The image displays 2 versions of the donut+icing.
To fix this in Blender 2.8x: Like mentioned by susu in the comment, you need to display the "camera" icon in the filter settings first. Then you can enable/disable the rendering of objects or whole collections in the ...
This looks to be artifacts caused by JPEG or other image compression. JPEG achieves its compression (grossly simplified) by splitting the image into a series of small squares and using transforms to effectively 're-use' squares which are very similar. This is fine for images since the slight innaccuracies are not normally visible to the person viewing the ...
I found that my selection of the baking options was the problem.
Initially I unticked everything except "Ambient Occlusion" (following a few online videos) - this left the primary baking type to "Combined", with direct and indirect light and Ambient Occlusion ticked.
I bounced around online for a while before going in to look ...