用于选择颜色的轨迹栏。使用 C++、opencv

Question

在我的项目中，用户应该为某个进程选择一种颜色。互联网上有一些应用程序。他们为颜色的 RGB 值创建了三个轨迹栏，但我不想那样做。我想在下面创建一个跟踪栏或类似的东西。

如何创建这样的轨迹栏？和

如何获取标记所在颜色的 RGB 值？

Answer 1

OpenCV GUI 功能并不丰富。您可能想使用Qt 或类似的工具来创建一个漂亮的 GUI，并且仍然在 OpenCV 中进行图像处理。

关于 OpenCV 上的跟踪栏，您可能希望使用 HSV（色相、饱和度、值）颜色空间而不是 RGB。修复S=255和V=255，您可以通过在[0, 180]范围内更改H来选择颜色。请注意，在 OpenCV for CV_8UC3 图像中，HSV 的范围是：

H in [0, 180]
S,V in [0, 255]

以下示例可能会为您提供一些关于如何使用轨迹栏和色调值的提示：

#include <opencv2/opencv.hpp>
using namespace cv;

Mat3b rgb;
Mat3b hsv;

void on_trackbar(int hue, void*)
{
    hsv.setTo(Scalar(hue, 255, 255));
    cvtColor(hsv, rgb, COLOR_HSV2BGR);
    imshow("HSV", rgb);
}

int main(int argc, char** argv)
{
    // Init images
    rgb = Mat3b(100, 300, Vec3b(0,0,0));
    cvtColor(rgb, hsv, COLOR_BGR2HSV);

    /// Initialize values
    int sliderValue = 0;

    /// Create Windows
    namedWindow("HSV", 1);

    /// Create Trackbars
    createTrackbar("Hue", "HSV", &sliderValue, 180, on_trackbar);

    /// Show some stuff
    on_trackbar(sliderValue, NULL);

    /// Wait until user press some key
    waitKey(0);
    return 0;
}

Answer 2

我生成图像，然后使用setMouseCallback 获取鼠标点击位置并手动绘制滑块。抱歉，我无法提供 C++ 代码 sn-p。

source code in Python 仅供参考。见on_mouse_event方法：

import cv2
import numpy as np


class SliderHSV:
    SLIDER_H = 16  # px
    sliding = False

    def __init__(self, window_name):
        self.window_name = window_name
        self.pt = 0, 0
        h_comp = np.uint8([np.linspace([0, 255, 255], [179, 255, 255], 180)])
        h_comp = np.broadcast_to(h_comp, (self.SLIDER_H, 180, 3))
        self.h_comp = cv2.cvtColor(h_comp, cv2.COLOR_HSV2BGR)
        self.tpl_hsv = np.uint8(  # This is very very slow!
            [(0, i, j) for i in np.linspace(0, 255, 256) for j in np.linspace(0, 255, 256)]
        ).reshape(256, 256, 3)
        self.set_value(0)
        cv2.setMouseCallback(window_name, self.on_mouse_event, param=self.window_name)
        cv2.setMouseCallback("Sat-Bri", self.on_mouse_event)

    def on_mouse_event(self, event, x, y, flags, param):
        # https://docs.opencv.org/4.x/db/d5b/tutorial_py_mouse_handling.html
        if event == cv2.EVENT_LBUTTONDOWN:
            self.sliding = True
            if param == self.window_name:
                self.set_value(x)
            else:
                self.pt = x, y
        elif event == cv2.EVENT_MOUSEMOVE:
            if self.sliding:
                if param == self.window_name:
                    self.set_value(x)
                else:
                    self.set_rect(self.pt, (x, y))
        elif event == cv2.EVENT_LBUTTONUP:
            self.sliding = False

    def set_rect(self, pt1, pt2):
        pt1 = max(min(pt1[0], 255), 0), max(min(pt1[1], 255), 0)
        pt2 = max(min(pt2[0], 255), 0), max(min(pt2[1], 255), 0)
        sv = self.sv.copy()
        cv2.rectangle(sv, pt1, pt2, (255, 255, 255))
        sh_y1 = (24, 12) if pt2[1] > pt1[1] else (-12, 0)
        sh_y2 = (0, -12) if pt2[1] > pt1[1] else (24, 12)
        cv2.putText(sv, f"Sat.{pt1[1]}", (pt1[0], pt1[1] + sh_y1[1]), cv2.FONT_HERSHEY_PLAIN, 0.75, 0, lineType=cv2.LINE_AA)
        cv2.putText(sv, f"Br.{pt1[0]}", (pt1[0], pt1[1] + sh_y1[0]), cv2.FONT_HERSHEY_PLAIN, 0.75, 0, lineType=cv2.LINE_AA)
        cv2.putText(sv, f"Sat.{pt2[1]}", (pt2[0] - 45, pt2[1] + sh_y2[1]), cv2.FONT_HERSHEY_PLAIN, 0.75, 0, lineType=cv2.LINE_AA)
        cv2.putText(sv, f"Br.{pt2[0]}", (pt2[0] - 45, pt2[1] + sh_y2[0]), cv2.FONT_HERSHEY_PLAIN, 0.75, 0, lineType=cv2.LINE_AA)
        cv2.imshow("Sat-Bri", sv)

    def set_value(self, hue):
        hue = min(hue, 179)
        hue = max(hue, 0)
        h_comp = self.h_comp.copy()
        cv2.line(h_comp, (hue, 0), (hue, self.SLIDER_H), (255, 255, 255), 2)
        cv2.putText(h_comp, f"Hue {hue}", (0, self.SLIDER_H), cv2.FONT_HERSHEY_PLAIN, 1, 0, lineType=cv2.LINE_AA)
        self.sv = self.create_sat_br_rect(hue)
        cv2.imshow(self.window_name, h_comp)
        cv2.imshow("Sat-Bri", self.sv)

    def create_sat_br_rect(self, hue):
        self.tpl_hsv[:, :, 0] = hue
        return cv2.cvtColor(self.tpl_hsv, cv2.COLOR_HSV2BGR)


SliderHSV("HSV slider")
while(1):
    if cv2.waitKey(100) & 0xFF == 27:
        break