is there any way to insert QPixmap object in html?

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Simple situation: I have an object, which has a QPixmap member. Object first created (pixmap is null now), then pixmap readed from data base and inserted in obj

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后悔当初

2021-01-05 22:55
I know this is an old question, but here is another option.

I had a similar issue with images in QToolTip. I could reference images from disk fine, but the default scaling behavior is non-smooth and looked terrible. I reimplemented my own tooltip class and used a custom QTextDocument class so that I could override QTextDocument::loadResource().

In your case, you can specify a keyword in the img src attribute. Then in your implementation of loadResource() return the QPixmap identified with the keyword.

Here is the basic code (untested in this context):
```
class MyTextDocument : public QTextDocument
{
protected:
  virtual QVariant loadResource(int type, const QUrl &name)
  {
    QString t = name.toString();
    if (t == myKeyword)
      return myPixmap;
    return QTextDocument::loadResource(type, name);
  }
};

class MyLabel : public QFrame
{
public:
  MyLabel(QWidget *parent)
  : QFrame(parent)
  , m_doc(new MyTextDocument(this))
  { }

  virtual void paintEvent(QPaintEvent *e)
  {
    QStylePainter p(this);
    // draw the frame if needed

    // draw the contents
    m_doc->drawContents(&p);
  }
};
```
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没有蜡笔的小新

2021-01-05 22:55

I put this in another answer to be able to format the code. I wrote the following program and it works as intended:

#include <QtGui>

int main(int argc, char *argv[])
{
    QApplication app(argc, argv);
    QWidget window;
    window.resize(320, 240);
    window.show();
    window.setWindowTitle(
        QApplication::translate("toplevel", "Top-level widget"));
    QLabel* label = new QLabel(&window);
    label->setTextFormat(Qt::RichText);
    QString text = "<html><h1>Test</h1>here is an image: ";
    QPixmap pixmap("testicon.jpg");
    QByteArray byteArray;
    QBuffer buffer(&byteArray);
    pixmap.save(&buffer, "PNG");
    QString url = QString("<img src=\"data:image/png;base64,") + byteArray.toBase64() + "\"/>";
    text += url;
    text += "</html>";
    label->setText(text);

    label->move(100, 100);
    label->show();
    return app.exec();
}

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长发绾君心

2021-01-05 23:01
If you only want to display a QPixmap in a QLabel, you should use QLabel::setPixmap. You can construct the pixmap in memory by using QPixmap::loadFromData.

If you want to display a memory pixmap in HTML, e.g. in a QWebView, you can use
```
    QByteArray byteArray;
    QBuffer buffer(&byteArray);
    pixmap.save(&buffer, "PNG");
    QString url = QString("<img src=\"data:image/png;base64,") + byteArray.toBase64() + "\"/>";
```
(untested)

QLabel::setText does not work with HTML but with rich-text. I do not know if the data: protocol is supported by the Qt rich-text implementation.

Another way to insert a pixmap into a QWebView would be to use a subclass of QNetworkAccessManager and reimplement its createRequest() function to check for URLs with your own protocol ("myprot:") and insert the pixmap data there. But this looks like overkill.
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广开言路

2021-01-05 23:05

This is my two cents about serializing/deserializing QPixmap to/from Base64 e strings. I've included methods to load/save the image as a text file but also two simple toBase64() and fromBase64() that help with HTML, SQL or JSON encoding.

#include "b64utils.h"
#include <QBuffer>
#include <QFile>
#include <QTextStream>

/**
 * Serializes a QPixmap object into a Base64 string
 */
QString B64Utils::toBase64(QPixmap *pixmap) {
    // Convert the pixel map into a base64 byte array
    QBuffer *buffer = new QBuffer;
    pixmap->save(buffer, "png");
    QByteArray b64 = buffer->data().toBase64();
    QString *b64Str = new QString(b64);
    return *b64Str;
}

/**
 * Serializes a QPixmap object into a Base64 string and save it to a file
 */
bool B64Utils::savePixmapToBase64(QPixmap *pixmap, QString filePath) {
    // Opens a file for writing text
    QFile file(filePath);
    if (!file.open(QIODevice::WriteOnly | QFile::Text)) return false;

    // Write the Base64 string into the file
    QTextStream stream(&file);
    stream << toBase64(pixmap);
    file.close();

    return true;
}

/**
 * Deserializes a Base64 string, representing an image, into a QPixmap
 */
QPixmap* B64Utils::fromBase64(QString b64Str) {
    QPixmap *pixmap = new QPixmap;
    pixmap->loadFromData(QByteArray::fromBase64(b64Str.toUtf8()));
    return pixmap;
}

/**
 * Retrieves a Base64 string, representing an image, from a file and deserializes it into a QPixmap
 */
QPixmap* B64Utils::loadPixmapFromBase64(QString filePath) {
    // Opens a file for reading text
    QFile file(filePath);
    if (!file.open(QFile::ReadOnly | QFile::Text)) return nullptr;

    // Reads the contents of the file into a string
    QTextStream in(&file);
    QString b64Str = in.readAll();
    file.close();

    return fromBase64(b64Str);
}

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