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