qml+opencv（一）

前言

忽然想起opencv，一直想作人臉識別，但是理論基礎太水，只能慢慢來，去年學習了一會，而後公司讓我去搞app和網絡，就一直擱着，如今學習qml，忽然想能不能在qml裏面使用opencv，因此就有了這篇文章。

QQuickItem和QObject

在QML中，可視化的基礎組件是Item，不可視化的就是QtObject，它們對應C++中的QQuickItem和QObject類，擴展QML組件一個繼續基於QML中的Item擴張，還有就是繼承QQuickItem，咱們想把opencv加到QML中，那麼只有繼承QQuickItem了。
怎麼使用，那還要看QML新的渲染機制，Qt5的QML渲染基於OpenGL，其場景的渲染在單獨的線程進行，咱們須要須要QQuickItem返回可以描述場景的對象，就是QSGNode。實現QQuick的updatePaintNode函數就OK了，咱們在updatePaintNode，描述怎麼渲染。

類的關係

OpenCVcapture繼承QOjbect，其是圖像捕獲的基類，OpenCVcamera是OpenCVcapture子類，完成從攝像頭捕獲數據。OpenCVaction類封裝了opencv圖像算法操做。OpenCVshowFrame繼承QQuickItem，實現可視化。

#include <QApplication>
#include <QQmlApplicationEngine>
#include <QtQml/qqml.h>
#include "opencvcamera.h"
#include "opencvshowframe.h"

int main(int argc, char *argv[])
{
    QApplication app(argc, argv);

    qmlRegisterType<OpenCVcamera>("OpenCV", 1, 0, "OpenCVcamera");
    qmlRegisterType<OpenCVshowFrame>("OpenCV", 1, 0, "OpenCVshowFrame");

    QQmlApplicationEngine engine;
    engine.load(QUrl(QStringLiteral("qrc:/main.qml")));

    return app.exec();
}

import QtQuick 2.4
import QtQuick.Controls 1.3
import QtQuick.Window 2.2
import QtQuick.Dialogs 1.2
import OpenCV 1.0

ApplicationWindow {
    title: qsTr("Hello World")
    width: 640
    height: 480
    visible: true

    menuBar: MenuBar {
        Menu {
            title: qsTr("&File")
            MenuItem {
                text: qsTr("&Open")
                onTriggered: {

                    //messageDialog.show(qsTr("Open OpenCV triggered"));
                    opencvCamera.m_run = true
                }

            }
            MenuItem {
                text: qsTr("&Close")
                onTriggered: {

                    //messageDialog.show(qsTr("Open OpenCV triggered"));
                    opencvCamera.m_run = false
                }

            }
            MenuItem {
                text: qsTr("E&xit")
                onTriggered: Qt.quit();
            }
        }
    }

    OpenCVcamera {
        id:opencvCamera
        m_cameraId: 1
        m_run: false

        //width: 320
        //height: 240
    }

    OpenCVshowFrame {
        anchors.centerIn: parent
        id:opencvShowFrame
        m_capture: opencvCamera
        m_frameRate: 33
        m_run: true
        width: 480
        height: 320
    }


    MessageDialog {
        id: messageDialog
        title: qsTr("May I have your attention, please?")

        function show(caption) {
            messageDialog.text = caption;
            messageDialog.open();
        }
    }
}

效果

我封裝了輪廓掃描的算法操做。

updatePaintNode

QSGNode* OpenCVshowFrame::updatePaintNode(QSGNode *old, UpdatePaintNodeData *)
{
    QSGSimpleTextureNode *texture = static_cast<QSGSimpleTextureNode*>(old);
    if (texture == NULL) {
        texture = new QSGSimpleTextureNode();
    }
    QImage img;
    IplImage *iplImage = NULL;
    IplImage *out = NULL;
    if (m_capture) {
        iplImage = static_cast<OpenCVcapture*>(m_capture)->getFrame();
    }
    if (iplImage != NULL) {
        out = doActions(iplImage);
        uchar *imgData = (uchar *)out->imageData;
        //qDebug() << out->depth << out->nChannels;
        img = QImage(imgData, out->width, out->height, QImage::Format_RGB888);
    } else {
        img = QImage(boundingRect().size().toSize(), QImage::Format_RGB888);
    }
    QSGTexture *t = window()->createTextureFromImage(img.scaled(boundingRect().size().toSize()));
    if (t) {
        QSGTexture *tt = texture->texture();
        if (tt) {
            tt->deleteLater();
        }
        texture->setRect(boundingRect());
        texture->setTexture(t);
    }
    if (out) {
        cvReleaseImage(&out);
    }
    return texture;
}

使用了QSGSimpleTextureNode，而後咱們將opencv的圖像，做爲一個QSGTexture，而後返回給渲染的線程進行場景的渲染。

這裏還要說下，Qt的QImage，不支持單通道的灰度圖，咱們須要轉換成RGB才能正確的顯示。