With internet access, such images can be introduced into the tabulation process as though they came from the official scanners.
Once introduced at that level, the cast vote records, vote totals, and all the other records are produced just as with legitimate votes. Voter rolls would be updated to reflect the proper number of "voters", paper ballots can be printed and backfilled as needed.
With centralized processing, the normal checks on ballot quantities that would occur at precincts is bypassed, as are most of the checks intended to ensure the integrity of an election. The risk to fraudsters is reduced since the need for ballot collection and purchasing is eliminated as well as the need for mules to deliver ballots to drop boxes. The critical pieces happen electronically, out of sight of observers and prying eyes, and leave few trails.
I have no evidence that such a scheme has actually been used, but I offer it to show how our current election systems can be compromised in ways that are hard to detect and prevent.
As I have written before, with current election systems, we can have no assurance that the results of any election are true and accurate expressions of the will of the voters.
Understand, I like technology. I design and use computer and other technical systems daily and appreciate the value of what they can do. It is, however, because of that experience that I know how such systems can be misused.
The last article of this series will look at what can be done to restore integrity to our elections. Some things we can do as individuals or small groups. Other things will require more effort. We should not be discouraged, though, because, although dire, the situation is not beyond redemption.