De-alpha blending
Posted: 2013-08-23T03:56:26-07:00
Hi all,
I have found that a couple of my pictures I usually put a watermark on... well I only have the watermarked version now.(but in quite high quality so noise won't be a huge issue)
I have the overlay that went on them, and I know the alpha blending value.
Since alpha blending is quite simple mathematically: result=alpha*overlay+(1-alpha)*original
This means to precision/rounding/errors, you can still get original = result * 1/(1-alpha) + overlay * alpha / (1 - alpha)
This is especially true in my case since the alpha value is fairly low, so there won't be huge errors.
I can not find any way to do any custom formula/use existing ones to do that.
Any ideas?
I have found that a couple of my pictures I usually put a watermark on... well I only have the watermarked version now.(but in quite high quality so noise won't be a huge issue)
I have the overlay that went on them, and I know the alpha blending value.
Since alpha blending is quite simple mathematically: result=alpha*overlay+(1-alpha)*original
This means to precision/rounding/errors, you can still get original = result * 1/(1-alpha) + overlay * alpha / (1 - alpha)
This is especially true in my case since the alpha value is fairly low, so there won't be huge errors.
I can not find any way to do any custom formula/use existing ones to do that.
Any ideas?
