OPENCV Official Document Learning record (3)

To change the brightness and contrast of an image:

Formula:

Code:

1#include <opencv2\opencv.hpp>2#include <iostream>3#include <string>4 5 #pragmaComment (linker, "/subsystem:\" windows\ "/entry:\" Maincrtstartup\ "")6 7 using namespacestd;8 using namespaceCV;9 Ten voidShow (std::stringname,mat img) One { A Namedwindow (name, cv_window_autosize); - imshow (Name, IMG); - } the  - intMain () - { -Mat img = Imread ("Lena.png"); +Mat new_img =Mat::zeros (Img.size (), Img.type ()); -  +     DoubleAlpha =2.2; A     intBeta = -; at      for(inty =0; Y < img.rows; ++y) -     { -          for(intx =0; x < Img.cols; ++x) -         { -              for(intc =0; C <3; ++c) -             { inNew_img.at<vec3b> (y, x) [c] = static_cast<uchar> (alpha* (img.at<vec3b> (y, x) [C]) +beta); -             } to         } +     } -Show ("Re", IMG); theShow ("Bright", new_img); *Imwrite ("./after/bright.png", new_img); $ Waitkey ();Panax Notoginseng     return 0; -}

Results:

(I don't know why my results are not the same as the examples, and I might have calculated errors)

Where we are using

New_img.at<vec3b> (y, x) [C]

Get the value of the channel, use Saturate_cast to do data overflow protection;

Alternatively, you can convert directly using a simpler function:

1#include <opencv2\opencv.hpp>2#include <iostream>3#include <string>4 5 #pragmaComment (linker, "/subsystem:\" windows\ "/entry:\" Maincrtstartup\ "")6 7 using namespacestd;8 using namespaceCV;9 Ten voidShow (std::stringname,mat img) One { A Namedwindow (name, cv_window_autosize); - imshow (Name, IMG); - } the  - intMain () - { -Mat img = Imread ("Lena.png"); +Mat new_img =Mat::zeros (Img.size (), Img.type ()); -     DoubleAlpha =2.2; +     intBeta = -; AImg.convertto (New_img,-1, alpha, beta); atShow (" After", new_img); - Waitkey (); -     return 0; -}

At this point the result is similar to the example:

OPENCV Official Document Learning record (3)