OpenCV 任意曲线(S型等)调整图像色调，对比度小工具 C++
色调变换
改善图像色调的变换通常交互的选择。其概念是实验性的调整图像的亮度和对比度，以便在合适的灰度范围提供最多的细节。
彩色本身并不改变。在RGB和CMYK空间中，这意味着使用相同的变换函数映射3个(或4个)彩色分量。在HSI中则改进了亮度分量；
下面显示了3个常见的色调不平衡的几个典型变换----平淡的，较亮的，较暗的图像。
S型曲线可以增强对比度，凹凸曲线分别减小、增加亮度。
下图是S曲线调整后的效果：
凹曲线降低亮度
凸曲线增强亮度：
单独修改RGB中的某一个通道，会改变色调；
R通道上凸，色调偏红；
R通道下凹，色调偏青色（蓝绿色），相当于红色的补色；G 、B通道同理。
代码实现：
实现两个类，Curve 和 Curves 在文件Curves.cpp中
下面是主函数实现：
/*
* test_Curves
*
* Created on: 2019.03.21
* Author: cui
*/
#include <cstdio>
#include <iostream>
#include "opencv2/core.hpp"
#include "opencv2/imgproc.hpp"
#include "opencv2/highgui.hpp"
#include "Curves.hpp"
using namespace std;
using namespace cv;
static string window_name = "Photo";
static Mat src;
static string curves_window = "Adjust Curves";
static Mat curves_mat;
static int channel = 0;
Curves curves;
static void invalidate()
{
curves.draw(curves_mat);
imshow(curves_window, curves_mat);
Mat dst;
curves.adjust(src, dst);
imshow(window_name, dst);
int y, x;
uchar *p;
y = 150; x = 50;
p = dst.ptr<uchar>(y) + x * 3;
cout << "(" << int(p[2]) << ", " << int(p[1]) << ", " << int(p[0]) << ") ";
y = 150; x = 220;
p = dst.ptr<uchar>(y) + x * 3;
cout << "(" << int(p[2]) << ", " << int(p[1]) << ", " << int(p[0]) << ") ";
y = 150; x = 400;
p = dst.ptr<uchar>(y) + x * 3;
cout << "(" << int(p[2]) << ", " << int(p[1]) << ", " << int(p[0]) << ") " << endl;
}
static void callbackAdjustChannel(int , void *)
{
switch (channel) {
case 3:
curves.CurrentChannel = &curves.BlueChannel;
break;
case 2:
curves.CurrentChannel = &curves.GreenChannel;
break;
case 1:
curves.CurrentChannel = &curves.RedChannel;
break;
default:
curves.CurrentChannel = &curves.RGBChannel;
break;
}
invalidate();
}
static void callbackMouseEvent(int mouseEvent, int x, int y, int flags, void* param)
{
switch(mouseEvent) {
case CV_EVENT_LBUTTONDOWN:
curves.mouseDown(x, y);
invalidate();
break;
case CV_EVENT_MOUSEMOVE:
if ( curves.mouseMove(x, y) )
invalidate();
break;
case CV_EVENT_LBUTTONUP:
curves.mouseUp(x, y);
invalidate();
break;
}
return;
}
int main()
{
//read image file
src = imread("635c.tif");
if ( !src.data ) {
cout << "error read image" << endl;
return -1;
}
// resize(src,src,Size(), 0.5,0.5);
//create window
namedWindow(window_name);
imshow(window_name, src);
//create Mat for curves
curves_mat = Mat::ones(256, 256, CV_8UC3);
//create window for curves
namedWindow(curves_window);
setMouseCallback(curves_window, callbackMouseEvent, NULL );
createTrackbar("Channel", curves_window, &channel, 3, callbackAdjustChannel);
// 范例：用程序代码在Red通道中定义一条曲线
curves.RGBChannel.clearPoints();
curves.RGBChannel.addPoint( Point(0, 0) );
curves.RGBChannel.addPoint( Point(64, 27) );
curves.RGBChannel.addPoint( Point(127, 127) );
curves.RGBChannel.addPoint( Point(192, 229) );
curves.RGBChannel.addPoint( Point(256, 256) );
invalidate();
waitKey();
return 0;
}
全部代码和测试图片下载地址：