使用node.js中的opencv-node将24位RGB图像转换为8位灰度 [英] Converting 24bit RGB image to 8bit grayscale with opencv-node in node.js

问题描述

我正在尝试从连接到Raspberry Pi的网络摄像头捕获node.js中的图像.捕获可以很好地工作，但是现在当我要传输图像时，帧率和滞后会出现一些严重的问题.

现在我的第一个想法是将RGB图像转换为8位灰度，这应该将性能提高3倍(我希望..).

我正在为此使用node.js和opencv-node.现在，您可以在此处看到一些代码片段:

var startT = new Date().getTime();
var capture = new cv.VideoCapture();
var frame = new cv.Mat;
var grey = new cv.Mat;
var imgPath = __dirname + "/ramdisk/";
var frame_number = 0;

capture.open(0);

if (!capture.isOpened())
{
    console.log("aCapLive could not open capture!");
    return;
}

function ImgCap()
{
    var elapsed = (new Date().getTime() - startT) / 1000;

    capture.read(frame);
    cv.imwrite(imgPath+".bmp", frame);

    id = setImmediate(ImgCap);
}

ImgCap();

我试图使用类似的东西

cv.cvtColor(frame, grey, "CV_BGR2GRAY");

在读取图像之后，但是我只得到一些TypeError，说参数2必须是整数...我目前不知道该怎么办.我提到了 http://docs.opencv.org/doc/tutorials/introduction/load_save_image/load_save_image.html#explanation ，用于将rgb转换为灰度图像.

此外，我仍然不确定这是否会给MIT提供24位灰度图像而不是8位.

感谢您的任何帮助！ :)

解决方案

使用CV_BGR2GRAY代替"CV_BGR2GRAY".

前者是整数常数，后者是char *

并且，不用担心，这将是8位灰度.

I'm trying to capture images within node.js from a webcam connected to a Raspberry Pi. Capturing works fine, but now when I want to transmit the images I have some serious problems with framerate and lags.

Now my first idea was to convert the RGB images to 8bit grayscale, that should increase the performance by factor 3 (i hope..).

I'm using node.js and opencv-node for this. Here you can see some code snippet for the moment:

var startT = new Date().getTime();
var capture = new cv.VideoCapture();
var frame = new cv.Mat;
var grey = new cv.Mat;
var imgPath = __dirname + "/ramdisk/";
var frame_number = 0;

capture.open(0);

if (!capture.isOpened())
{
    console.log("aCapLive could not open capture!");
    return;
}

function ImgCap()
{
    var elapsed = (new Date().getTime() - startT) / 1000;

    capture.read(frame);
    cv.imwrite(imgPath+".bmp", frame);

    id = setImmediate(ImgCap);
}

ImgCap();

I tried to use something like

cv.cvtColor(frame, grey, "CV_BGR2GRAY");

after reading the image but i only get some TypeError saying that argument 2 has to be an integer... I dont know what to do at the moment. I referred to http://docs.opencv.org/doc/tutorials/introduction/load_save_image/load_save_image.html#explanation for converting a rgb to a grayscale image.

Beside I'm still not sure if this just gives mit a 24bit grayscale image instead of 8bit..?!

Thanks for any help in advance! :)

解决方案

use CV_BGR2GRAY instead of "CV_BGR2GRAY".

the former is an integral constant, the latter a char*

and, no fear, that will be 8bit grayscale.

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