用Cimg

Question

作为我现在正在工作的项目的一部分，我需要以类似于MATLAB的样式绘制矢量。在研究了我遇到的CIMG的一些可能性之后，它似乎很容易融入我的程序并且恰到好处地满足我的需求。我是C ++的新手，之前从未使用过Cimg。

按照指南中提供的一个例子，我到达了这个程序来绘制矢量（在本例中名为ecg_r），我的代码如下：

// Read command line argument   cimg_usage("Simple plotter of ECG signal");
const char *const formula = cimg_option("-f", "x", "Formula to plot");
const float x0 = cimg_option("-x0", 0.0f, "Minimal X-value");
const float x1 = cimg_option("-x1", 20.0f, "Maximal X-value");
int sizeecg = ecg_r.size();
const int resolution = cimg_option("-r", sizeecg, "Plot resolution");
const unsigned int nresolution = resolution>1 ? resolution : sizeecg;
const unsigned int plot_type = cimg_option("-p", 1, "Plot type");
const unsigned int vertex_type = cimg_option("-v", 1, "Vertex type");

// Create plot data.
CImg<double> values(1, nresolution, 1, 1, 0);

const unsigned int r = nresolution - 1;

for (int i1 = 0; i1 < sizeecg; ++i1)
{
    double xtime = x0 + i1*(x1 - x0) / r;
    values(0, i1) = ecg_r.at(i1);
}  

// Display interactive plot window.
values.display_graph(formula, plot_type, vertex_type, "X-axis", x0, x1, "Y-axis");

我在创建的显示窗口中看到的图像正是我所期待的，但是当我尝试使用以下命令将图像保存在bmp中时：

values.save_bmp("test.bmp");

图像是全黑的，如何保存我在显示功能中看到的图像？我昨天下午花了很多时间去找文件，但是找不到线索。

提前谢谢..

这是我想要做的MCVE，我希望能够在bmp中保存我在显示窗口中看到的内容。谢谢

#include "CImg.h"
#include <vector>

using namespace cimg_library;

int main(int argc, char** const argv)
{
    cimg_usage("Simple plotter of mathematical formulas");
    const char *const formula = cimg_option("-f", "sin(x)", "Formula to    plot");
    const float x0 = cimg_option("-x0", -5.0f, "Minimal X-value");
    const float x1 = cimg_option("-x1", 5.0f, "Maximal X-value");
    const int resolution = cimg_option("-r", 5000, "Plot resolution");
    const unsigned int nresolution = resolution>1 ? resolution : 5000;
    const unsigned int plot_type = cimg_option("-p", 1, "Plot type");
    const unsigned int vertex_type = cimg_option("-v", 1, "Vertex type");

    // Create plot data.
    CImg<double> values(1, nresolution, 1, 1, 0);

    const unsigned int r = nresolution - 1;

    for (int i1 = 0; i1 < resolution; ++i1)
    {
        double xtime = x0 + i1*(x1 - x0) / r;
        values(0, i1) = sin(xtime);
    }

    CImg<double> values2;
    values2 = values.display_graph(formula, plot_type, vertex_type, "X Axis", x0, x1, "Y Axis");
    values.normalize(0, 255);
    values.save_bmp("test.bmp");

}

Answer 1

更新答案

你完全错了，马克！您可以像这样拍摄情节快照。

#include "CImg.h"
#include <vector>

using namespace cimg_library;

int main(int argc, char** const argv)
{
    cimg_usage("Simple plotter of mathematical formulas");
    const char *const formula = cimg_option("-f", "sin(x)", "Formula to    plot");
    const float x0 = cimg_option("-x0", -5.0f, "Minimal X-value");
    const float x1 = cimg_option("-x1", 5.0f, "Maximal X-value");
    const int resolution = cimg_option("-r", 5000, "Plot resolution");
    const unsigned int nresolution = resolution>1 ? resolution : 5000;
    const unsigned int plot_type = cimg_option("-p", 1, "Plot type");
    const unsigned int vertex_type = cimg_option("-v", 1, "Vertex type");

    // Create plot data.
    CImg<double> values(1, nresolution, 1, 1, 0);

    const unsigned int r = nresolution - 1;

    for (int i1 = 0; i1 < resolution; ++i1)
    {
        double xtime = x0 + i1*(x1 - x0) / r;
        values(0, i1) = sin(xtime);
    }

    CImgDisplay disp;
    CImg<double> values2;
    values.display_graph(disp, plot_type, vertex_type, "X Axis", x0, x1, "Y Axis");
    disp.snapshot(values2);
    values2.save_bmp("result.bmp");
}

原始答案

如果有人知道更好的话，我很高兴被告知我完全错了，并告诉我们方式，但我不相信 CImg 会给你作为位图文件的情节就像你想要的那样。

所以，我使用 gnuplot 进行游戏。您的图像在屏幕上显示如下：

因此，作为一个粗略的近似，如果您对代码进行一些编辑，如下所示：

#include "CImg.h"
#include <iostream>
#include <fstream>
#include <vector>

using namespace cimg_library;
using namespace std;

int main(int argc, char** const argv)
{
    cimg_usage("Simple plotter of mathematical formulas");
    const char *const formula = cimg_option("-f", "sin(x)", "Formula to    plot");
    const float x0 = cimg_option("-x0", -5.0f, "Minimal X-value");
    const float x1 = cimg_option("-x1", 5.0f, "Maximal X-value");
    const int resolution = cimg_option("-r", 5000, "Plot resolution");
    const unsigned int nresolution = resolution>1 ? resolution : 5000;
    const unsigned int plot_type = cimg_option("-p", 1, "Plot type");
    const unsigned int vertex_type = cimg_option("-v", 1, "Vertex type");

    // Create plot data.
    CImg<double> values(1, nresolution, 1, 1, 0);

    const unsigned int r = nresolution - 1;

    ofstream data;
    data.open("plot.dat");

    for (int i1 = 0; i1 < resolution; ++i1)
    {
        double xtime = x0 + i1*(x1 - x0) / r;
        values(0, i1) = sin(xtime);
        double x=x0 + i1*(x1-x0)/nresolution;
        data << x << " " << values(0,i1) << endl;
    }
    data.close();

    CImg<double> values2;
    values2 = values.display_graph(formula, plot_type, vertex_type, "X Axis", x0, x1, "Y Axis");
    cout << "set terminal png size 900,600 enhanced font \"Helvetica,20\"" << endl;
    cout << "set output 'out.png'" << endl;
    cout << "set xrange [" << x0 << ":" << x1 << "]" << endl;
    cout << "set grid" << endl;
    cout << "set ylabel 'Y Axis'" << endl;
    cout << "set xlabel 'X Axis'" << endl;
    cout << "plot \"plot.dat\" with linespoint lc 4" << endl;
}

然后像这样运行：

./yourProgram | gnuplot

你会得到这个：