why is the differnce in subtracting two images and subtracting two matrices ?

2 次查看（过去 30 天）
Pramod Bhat
Pramod Bhat 2011-4-15
Hi, when you subtract two images we get another image which will be having no negative elements in it,ie intensity level below zero is assigned to Zero value. But when we subtract another two matrices,for example a=[1,2,4;4,6,8;6,8,9] and b=[4,6,9;4,1,3;4,2,7] we get another matrix [-3,-4,-5;0,5,4;2,6,2]. but this final matrix has some negative elements. my doubt is that,even if two images are saved in two variables(ie equivalent to two matrices) their subtraction always gives another matrix having no negative elements. but i want to get negative elements after subtracting them how to achieve this in MATLAB ? i need to sum all those -ve elements. plz help me...

请先登录，再回答此问题。

采纳的回答

Friedrich
Friedrich 2011-4-15
Hi Pramod,
I think this is related due the fact that an image is hold as an uint8 matrix and those have no sign. What you can do to get the negative values is to cast it,e.g. to int16 before:
difference = int16(A) - int16(B);
Friedrich

更多回答（0 个）

类别

在 Help Center 和 File Exchange 中查找有关 Images 的更多信息

标签

Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!

Translated by