Question

CImg<unsigned char> src("image.jpg");
int width = src.width();
int height = src.height();
unsigned char* ptr = src.data(10,10);

如何从rgb获取ptr？

Answer 1

在Ubuntu 10.04上测试，手工制作的3x3 RGB图像保存为test.png：

sudo apt-get install cimg-dev

源文件cimg_test.cpp：

#include <iostream>
using namespace std;

#include <CImg.h>
using namespace cimg_library;

int main()
{
    CImg<unsigned char> src("test.png");
    int width = src.width();
    int height = src.height();
    cout << width << "x" << height << endl;
    for (int r = 0; r < height; r++)
        for (int c = 0; c < width; c++)
            cout << "(" << r << "," << c << ") ="
                 << " R" << (int)src(c,r,0,0)
                 << " G" << (int)src(c,r,0,1)
                 << " B" << (int)src(c,r,0,2) << endl;
    return 0;
}

编译并运行：

g++ cimg_test.cpp -lX11 -lpthread -o cimg_test

./cimg_test 
3x3
(0,0) = R0 G0 B0
(0,1) = R255 G0 B0
(0,2) = R0 G255 B0
(1,0) = R0 G0 B255
(1,1) = R128 G128 B128
(1,2) = R0 G0 B128
(2,0) = R128 G0 B0
(2,1) = R0 G128 B0
(2,2) = R255 G255 B255

有效。

Answer 2

从the CImg documentation - 第34页第6.13节和第120页第8.1.4.16节 - 看起来data方法可以采用四个参数：x ，y，z和c：

T* data(const unsigned int x, const unsigned int y = 0, 
        const unsigned int z = 0, const unsigned int c = 0)

...其中c指的是颜色通道。我猜测如果你的图像确实是一个RGB图像，那么c使用0,1或2的值会给你在给定x, y位置的红色，绿色和蓝色分量

例如：

unsigned char *r = src.data(10, 10, 0, 0);
unsigned char *g = src.data(10, 10, 0, 1);
unsigned char *b = src.data(10, 10, 0, 2);

（但这只是猜测！）

修改

看起来CImg的操作符（）也以类似的方式工作：

unsigned char r = src(10, 10, 0, 0);

Answer 3

访问数据的最简单方法是使用()运算符：

unsigned char r = img(10,10,0,0);
unsigned char g = img(10,10,0,1);
unsigned char b = img(10,10,0,2);

你可能会感到困惑，因为CImg存储了非交错的原始数据。即您的原始数据存储在R1, R2, ..., G1, G2, ..., B1, B2, ...而不是R1, G1, B1, R2, G2, B2, ...，请参阅：http://cimg.eu/reference/group__cimg__storage.html

.data()只返回一个指针，所以要像上面那样直接访问数据：

CImg<unsigned char> src("image.jpg");
int width = src.width();
int height = src.height();
unsigned char* ptr = src.data(10,10);
unsigned char r = ptr[0];
unsigned char g = ptr[0+width*height];
unsigned char b = ptr[0+2*width*height];

如何通过cimg获得rgb值？

4 个答案: