Loading image from computer files save in database and display later

[Christian Ehrlicher]

@HoMa said in Loading image from computer files save in database and display later:

QPixmap pixmap("../sqlPixmap/image.jpg");
QByteArray ba;
QBuffer bu(&ba);
bu.open(QIODevice::WriteOnly);
pixmap.save(&bu);

Please check if the first line really works. Relaitve paths are not good since you don't know the current working directory of your program.

[GREYON]

@JonB thanks people for your help,after going through documentation and one of example which I was given a here ,I found out that the code below is one having a problem,it was storing a file in a data base as a file path and not as Byte.

QByteArray HOME::bigimage;
void HOME::on_commandLinkButton_clicked()
{
 // QByteArray bigimage;
 QString filename=QFileDialog::getOpenFileName(this,tr("Open image"),"/",tr("Image Files(*.png;*.jpg;*.bmp)"));
 bigimage +=filename;

 QPixmap pixmap=QPixmap(filename);
 ui->label_8->setText(filename);
}```

So I had to change to something like this and it worked.

QByteArray HOME::bigimage;
void HOME::on_commandLinkButton_clicked()
{
// QByteArray bigimage;
QString filename=QFileDialog::getOpenFileName(this,tr("Open image"),"/",tr("Image Files(.png;.jpg;*.bmp)"));

Qfile file(filename)
if(!file.open(QIODevice::ReadOnly) return;
bigimage=file.readAll();

[HoMa]

@Christian-Ehrlicher It really does. I change only the file name from what is here to ":memory:" (like in the line below, which is commented out) and the picture can no longer be retreived.

Here the code with all calls tested:

    try
    {
        QPixmap pixmap("../sqlPixmap/image.jpg");
        QByteArray ba;
        QBuffer bu(&ba);
        bu.open(QIODevice::WriteOnly);
        pixmap.save(&bu);
        if( pixmap.width ()<= 0 || pixmap.height () <= 0) throw "Loading image from file failed";

        QSqlDatabase db =QSqlDatabase::addDatabase ("QSQLITE");
        db.setDatabaseName ("../sqlPixmap/db.sqlite");
        //db.setDatabaseName (":memory:");
        if( ! db.open()) throw "database could not be opened";

        QSqlQuery v("SELECT sqlite_version()");
        Q_ASSERT(v.next());
        qDebug() << "sqlite version " << v.value (0).toString();

        QSqlQuery q ("CREATE TABLE t (c)"); // executes on creation

        q.prepare ("INSERT INTO t (c) VALUES (:pic)");
        q.bindValue (":pic", ba);
        if( ! q.exec()) throw "could not store data";

        /////////////////////////////////////////////

        q.prepare ("SELECT c FROM t");
        if( ! q.exec()) throw "failed in select query";

        if( ! q.next()) throw "failed to move to data set";

        QByteArray readBa =q.value (0).toByteArray ();
        if( 0 >= readBa.size ()) throw "returned data is empty";

        QPixmap readPic;
        readPic.loadFromData(readBa);
        ui->lbl->setPixmap (readPic);
        ui->lbl->setScaledContents (true);
    }
    catch(const char* error)
    {
        qDebug() << error;
        return;
    }

[JonB]

@GREYON
Not sure what happened to your QPixmap pixmap=QPixmap(filename); line now. After reading a QPixmap from a file (or elsewhere) you can/should always check bool QPixmap::isNull() const. That would cover e.g. "file not found" as well as "error reading contents of file as pixmap".

[GREYON]

This is the correct one

QByteArray HOME::bigimage;
void HOME::on_commandLinkButton_clicked()
{
// QByteArray bigimage;
QString filename=QFileDialog::getOpenFileName(this,tr("Open image"),"/",tr("Image Files(.png;.jpg;*.bmp)"));

Qfile file(filename)
if(!file.open(QIODevice::ReadOnly) return;
bigimage=file.readAll();

[JonB]

@HoMa said in Loading image from computer files save in database and display later:

QPixmap pixmap("../sqlPixmap/image.jpg");
db.setDatabaseName ("../sqlPixmap/db.sqlite");

As @Christian-Ehrlicher commented, you simply should not use a relative path here, as you just do not know where that will be. See my https://forum.qt.io/topic/138832/export-qtableview-to-pdf-with-a-push-button/8 to another user on the same matter.

[HoMa]

@JonB Thx for your efforts - I appreciate that. But this is a test program for the single purpose of playing around with sqlite, blobs (and meanwhile "in memory"). Anyone who wants to use the code will have to modify the path to the picture - no matter if it is absolute or relative. For this reason I think it makes no difference in this specific case.

[GREYON]

@HoMa thanks for that code I will try it as well

[HoMa]

Couldn't resist and created a version, which works also with an in memory database.
@GREYON : Pls check out https://github.com/Schachigel/Qt-QPixmap-2-SQLite.git

have fun!

[GREYON]

@HoMa okay thanks let me check bro