• qt 提高图片加载速度


    一,将图片在pc上解析,然后将解析文件放到qrc文件中,读取qrc文件。

     1,将图片解析后的二进制文件保存,源码如下,

         下载地址:https://files.cnblogs.com/files/senior-engineer/imageTest.rar

       main.cpp

    #include "widget.h"
    #include <QApplication>
    
    int main(int argc, char *argv[])
    {
        QApplication a(argc, argv);
        Widget w;
        w.show();
    
        return a.exec();
    }

      widget.h

    #ifndef WIDGET_H
    #define WIDGET_H
    
    #include <QWidget>
    
    namespace Ui {
    class Widget;
    }
    
    class Widget : public QWidget
    {
        Q_OBJECT
    
    public:
        explicit Widget(QWidget *parent = 0);
        ~Widget();
    
    private slots:
        void saveImageToFile();
        void refreshImage();
    
    private:
        Ui::Widget *ui;
    
    private:
        QString m_fileName;
        int m_imgWidth;
        int m_imgHeight;
    };
    
    #endif // WIDGET_H

      widget.cpp

    #include "widget.h"
    #include "ui_widget.h"
    #include <QImage>
    #include <QFile>
    #include <QDebug>
    #include <QResource>
    
    #define IMAG_BIT 3
    
    Widget::Widget(QWidget *parent) :
        QWidget(parent),
        ui(new Ui::Widget)
    {
        ui->setupUi(this);
        //m_fileName = "radio_but_eq_p.png";
        m_fileName = "bg.png";
        ui->imageName->setText(m_fileName);
    
    //    QResource resource;
    //    resource.setFileName(":/main_bg.png");
    //    const uchar* imageData = resource.data();
    //    QImage desImage = QImage(imageData, 800,480,QImage::Format_RGB32); //RGB32
    //    QPixmap pixmag;
    //    pixmag = QPixmap::fromImage(desImage);
    //    ui->oldImage->setPixmap(pixmag);
    
        QPixmap pixmap(":/main_bg.png");
        ui->oldImage->setPixmap(pixmap);
    
    //    QPixmap pixmag;
    //    pixmag.load(m_fileName);
    //    ui->oldImage->setPixmap(pixmag);
    
        connect(ui->start, SIGNAL(clicked(bool)), this, SLOT(saveImageToFile()));
        connect(ui->refresh, SIGNAL(clicked(bool)), this, SLOT(refreshImage()));
    }
    
    Widget::~Widget()
    {
        delete ui;
    }
    
    void Widget::saveImageToFile()
    {
        QImage image(m_fileName);
      //  QImage image = QImage(800,480,QImage::Format_RGB888); //RGB32
    
     //   image.load(m_fileName);
        int size = image.byteCount();
        int sizePerLine = image.bytesPerLine();
        int line = size / sizePerLine;
        m_imgWidth = image.width();
        m_imgHeight = image.height();
    
        qDebug() << "size:" <<size;
        qDebug() << "sizePerLine:" << sizePerLine;
        qDebug() << "line:" << line;
        qDebug() << "" << m_imgWidth;
    
        uchar* imgDataNew = image.bits();
    
        FILE *pf = fopen("newfile.png", "wb");
        if(pf == NULL)
            return;
        QFile file;
        file.open(pf, QIODevice::WriteOnly); //1
        for(int i = 0; i < line; i++)
        {
            uchar* lineData = image.scanLine(i);
            for(int j = 0; j < sizePerLine; j++)
            {
                file.write((char*)(lineData + j),1);
            }
        }
    
        file.close();
    
    //    QImage desImage = QImage(m_imgWidth,m_imgHeight,QImage::Format_RGB32); //RGB32
    
    //    //RGB分量值
    //    int b = 0;
    //    int g = 0;
    //    int r = 0;
    //    int a = 0;
    
    //    //设置像素
    //    for (int i=0;i < m_imgHeight;i++)
    //    {
    //        for (int j=0; j < m_imgWidth * 4;)
    //        {
    //            b = (int)*(imgDataNew + i * m_imgWidth * 4 + j);
    //            g = (int)*(imgDataNew + i * m_imgWidth * 4 + j + 1);
    //            r = (int)*(imgDataNew + i * m_imgWidth * 4 + j + 2);
    //            a = (int)*(imgDataNew + i * m_imgWidth * 4 + j + 3);
    //            desImage.setPixel(j / 4,i,qRgba(r,g,b,a));
    //            j = j + 4;
    //            //desImage.setPixel(j,i,qRgb(r,g,b));
    //        }
    //    }
    
    
    //    QPixmap pixmag;
    //    pixmag = QPixmap::fromImage(desImage);
    //    ui->newImage->setPixmap(pixmag);
    }
    
    void Widget::refreshImage()
    {
        QFile file(":/newfile.png");
        //if (!file.open(QIODevice::ReadOnly | QIODevice::Text))
        if (!file.open(QIODevice::ReadOnly))
            return;
        QByteArray array = file.readAll();
        //file.close();
        char* imgDataNew = array.data();
    
        QImage desImage = QImage(m_imgWidth,m_imgHeight,QImage::Format_RGB32); //RGB32
    
        //RGB分量值
        int b = 0;
        int g = 0;
        int r = 0;
        int a = 0;
    
        //设置像素
        for (int i=0;i < m_imgHeight;i++)
        {
            for (int j=0; j < m_imgWidth * 4;)
            {
                b = (int)*(imgDataNew + i * m_imgWidth * 4 + j);
                g = (int)*(imgDataNew + i * m_imgWidth * 4 + j + 1);
                r = (int)*(imgDataNew + i * m_imgWidth * 4 + j + 2);
                a = (int)*(imgDataNew + i * m_imgWidth * 4 + j + 3);
                desImage.setPixel(j / 4,i,qRgba(r,g,b,a));
                j = j + 4;
                //desImage.setPixel(j,i,qRgb(r,g,b));
            }
        }
    
    
        QPixmap pixmag;
        pixmag = QPixmap::fromImage(desImage);
        ui->newImage->setPixmap(pixmag);
    
    //    QImage desImage ;
    //    if(IMAG_BIT == 3)
    //        desImage = QImage(m_imgWidth,m_imgHeight,QImage::Format_RGB888); //RGB24
    //    else if(IMAG_BIT == 4)
    //        desImage = QImage(m_imgWidth,m_imgHeight,QImage::Format_RGB32); //RGB32
    
    //    //RGB分量值
    //    char b = 0;
    //    char g = 0;
    //    char r = 0;
    //    char a = 0;
    
    //    //设置像素
    //    for (int i=0;i < m_imgHeight;i++)
    //    {
    //        for (int j=0; j < m_imgWidth * IMAG_BIT;)
    //        {
    //            b = (int)*(imgDataNew + i * m_imgWidth * IMAG_BIT + j);
    //            g = (int)*(imgDataNew + i * m_imgWidth * IMAG_BIT + j + 1);
    //            r = (int)*(imgDataNew + i * m_imgWidth * IMAG_BIT + j + 2);
    //            if(IMAG_BIT == 4)
    //            {
    //                a = (int)*(imgDataNew + i * m_imgWidth * IMAG_BIT + j + 3);
    //                desImage.setPixel(j / IMAG_BIT,i,qRgba(r,g,b,a));
    //            }
    //            else if(IMAG_BIT == 3)
    //            {
    //                desImage.setPixel(j / IMAG_BIT, i, qRgb(r,g,b));
    //            }
    //            j = j + IMAG_BIT;
    //        }
    //    }
    
    //    QPixmap pixmag;
    //    pixmag = QPixmap::fromImage(desImage);
    //    ui->newImage->setPixmap(pixmag);
    }

     二,此方法已经试过了,但是open文件时候很耗时,大概200~300ms

    (!file.open(QIODevice::ReadOnly))

    二,直接加图片放到qrc文件中,读取qrc文件

      一,qrc文件中添加图片资源

      二,再.pro文件中添加qrc文件

             例如:  RESOURCES     = res.qrc

      三,在程序中使用图片文件时候,通过“:文件名”

            例如:image=new QImage(":1.png");

      四,此方法原理对应qt官方文档地址:http://doc.qt.io/qt-5/resources.html

    三,将图片转换为数组,然后将图片画到界面上(适用绘制字体)

    一,用下面工具将图片转换为数组

    https://files.cnblogs.com/files/senior-engineer/fileToC.rar

    二,更具对应数每个bit对应的是1或者是0绘制黑白

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  • 原文地址:https://www.cnblogs.com/senior-engineer/p/9548271.html
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