What is the formula for extracting the src from a calculated blendmode?

How does one go about using a alpha blending formula to achieve the src rgb color from the resultant 开发者_Go百科of the 2 blended together

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Well, you can just reorder the alpha blending equation

Value = (1 − α) · Value₀ + α · Value₁

However, there are four variables in that equation: α, Value, Value₀ and Value₁. You need to know three of them to calculate the fourth. So in your case you know the resulting color, Value, the α and maybe Value₀. You can then reorder the equation as follows:

−α · Value₁ = (1 − α) · Value₀ − Value

Value₁ = (−1/α) · ((1 − α) · Value₀ − Value)

That is, if I understood you correctly. Which might not be the case. You might want to clarify your question.