Investors & landlords

So if I understand this right, if someone was to all of sudden come into a large sum of money, like winning a lottery or having a large sum of a foreign currency that revalued creating a large windfall, the IRS would base there percentage of capital gains on the current yearly income your making at the time? like if your making say twenty five thousand a year would be X% and if your making five hundred thousand a year would be much higher percentage, not just one capital gain percent based on the type and amount of the windfall?