We are calculating the opacity using the following formula
float alpha = 1 - transparency ; // transparency is a float value .
Now the user will be supplying transparency in int format ... What changes should I make to get the opacity ?
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sameer karjatkar
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3... multiply by 255? Did you give this any thought at all? – Botje Oct 04 '19 at 09:08
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You will need to know the range of possible alpha values in the floating point format. Assuming the range of possible floating point alpha values is between 0.0 and 1.0 (inclusive), then this will work:
#include <cmath>
long lalpha{std::lround(alpha * 255)};
In case the upper bound on the floating point alpha range is not equal to 1.0, you can divide the floating point alpha value by the upper bound to normalize to a range from 0.0 to 1.0 inclusive.
Ton van den Heuvel
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Is opacity and transparency same ? In the existing code I see we are doing double alpha = 1- transparency; – sameer karjatkar Oct 04 '19 at 09:25
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Opacity is the opposite of transparency. An object that is fully opaque is not transparent, and vice versa. – Ton van den Heuvel Oct 04 '19 at 09:27
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Ok ..so I have to calulate opacity from transparency ..will ur formula hold good then ? – sameer karjatkar Oct 04 '19 at 09:29
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