Always getting 255 while adding.

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Sneha 2018-1-17

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评论： Sneha 2018-1-17

I had a matrix of Red values of an image R of size 65536*1 and i had 3 integer values RR(1),GG(1) and BB(1). I need to add R(1)+GG(1)+BB(1) to get new RR(2). Similarly for the other two. But while am doing Rcomponent = R(1)+GG(1)+BB(1); its showing 255 always. [here R(1) = 68 , GG(1) = 173 , BB(1) = 147] Please help me with this. R matrix is of uint8.

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Greg 2018-1-17

Hint: What's the maximum value a uint8 can hold? What happens when you exceed that value?

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Answer 1

James Tursa 2018-1-17

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All of the integer types clip resulting values at both ends. So for uint8 it clips the lower end at 0 and the upper end at 255. You can convert to double first if you want to see what you are apparently expecting. E.g.,

Rcomponent = double(R) + double(GG) + double(BB);