Increment the value of each pixel of an image - c++

Question

I have an image. I want to modify the image in such a way that the value of each pixel is increased by a particular margin. Next I want to save the newly created image and display it.
I tried changing each pixel value but was only able to set it to constant value. I don't want all the pixels to be constant but their value should increase by (lets say) 50.
#include <iostream>
#include "opencv2/highgui/highgui.hpp"
using namespace std;
using namespace cv;
int main()
{
Mat image;
image = imread("/home/rohit_136/Desktop/image.jpg",CV_LOAD_IMAGE_UNCHANGED);
for (int i = 0; i < image.cols; i++) {
for (int j = 0; j < image.rows; j++) {
Vec3b intensity = image.at<Vec3b>(j, i)=50
}
}
return 0;
}

Answer 1

Vec3b is a vector which contains 3 bytes (chars). Each byte denotes the value of an individual BGR (blue, green, red) or RGB channel. You should traverse this vector and modify each channel independently. Be careful, because we are talking about bytes, each byte should take a value between 0 and 255. I suggest setting a threshold for avoiding overflow.
Note: if you don't care about alpha channel, I suggest loading your image with CV_LOAD_IMAGE_COLOR. This will ensure that your image is loaded in the BGR format.

Answer 2

cv::Mat Image =cv::imread("image.jpg");
uint8_t * orig_ptr = (uint8_t*)Image.data;
for (int y = 0; y < Image.rows; y++)
{
for (int x = 0; x < Image.cols; x++)
{
/*Reading Pizel Values*/
int R = orig_ptr[x * 3 + y*Image.step + 2];/*R -Pixel*/
int G = orig_ptr[x * 3 + y*Image.step + 1];/*G-Pixel*/
int B = orig_ptr[x * 3 + y*Image.step]; /*B-Pixel*/
/*Updating Values*/
orig_ptr[x * 3 + y*Image.step + 2] = cv::saturate_cast<uint8_t>(R + 50);
orig_ptr[x * 3 + y*Image.step + 1] =cv::saturate_cast<uint8_t>(G + 50);
orig_ptr[x * 3 + y*Image.step]=cv::saturate_cast<uint8_t>(B + 50);
}
}