在OpenCV中使用CV_AA标志绘制线不会产生抗锯齿的线 [英] Drawing a line in OpenCV with CV_AA flags is not producing an anti-aliased line

问题描述

我无法获得cv :: line来绘制设置了CV_AA标志的抗锯齿线.这是示例代码来说明:

I am unable to get cv::line to draw an anti-aliased line with CV_AA flags set. Here is example code to illustrate:

#include<iostream>
#include<opencv2/opencv.hpp>

using namespace std;

int main(int argc, char* argv[])
{
    cv::Mat base(100, 100, CV_32F);

    cv::Point2i p1(20, 20);
    cv::Point2i p2(70, 90);

    cv::line(base, p1, p2, cv::Scalar(1.0), 1, CV_AA); // 1 pixel thick, CV_AA == Anti-aliased flag

    cv::namedWindow("line test", CV_NORMAL);
    cv::imshow("line test", base);
    cv::waitKey(0);

    return 0;
}

我尝试使用cv :: Point2d代替cv :: Point2i，但没有发现任何区别. (i ==整数，d ==两倍)我也尝试过使像素宽度大于1，但仍然没有AA.

I have tried using cv::Point2d instead of cv::Point2i and found no difference. (i == integer, d == double) I have also tried making the pixel width larger than 1, but there is still no AA.

但是，这确实适用于CV_8U(8位无符号)映像，而不是我在这里使用的CV_32F(32位浮点)映像. (对于CV_8U，必须将cv :: Scalar(255)而不是cv :: Scalar(1.0)传递到行函数中进行比较)

However, this does work with a CV_8U (8-bit unsigned) image, as opposed to CV_32F (32-bit float) image that I have here. (For CV_8U, you must pass cv::Scalar(255) instead of cv::Scalar(1.0) into the line function to compare)

我认为当前的解决方法是从CV_8U图像开始然后进行转换，但是有没有一种简单的方法可以仅通过CV_32F图像来实现该功能，而无需我编写自己的抗锯齿功能?

I suppose a current work-around would be to start with a CV_8U image then convert, but is there a straightforward way to do it with just an CV_32F image that doesn't require me to write my own anti-aliasing function?

我想念什么吗?

OpenCV文档: cv :: line reference

OpenCV docs: cv::line reference

推荐答案

./core/src/drawing.cpp:1569
void line( Mat& img, Point pt1, Point pt2, const Scalar& color,
       int thickness, int line_type, int shift )
{
    if( line_type == CV_AA && img.depth() != CV_8U )
        line_type = 8;
    //omitted
}

源代码指出，只要深度不是CV_8U，它将使用8位连接法绘制.

The source code states that as long as the depth is not CV_8U, it will draw using 8-connected method.

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