Reading image from QSqlTableModel

gabor53

Hi,
I'm trying to read an image from an SQLite db using QSqlTableModel (and display it in a TableView). In the delegate I have the following code:

void FixViewDelegate::setModelData(QWidget* editor, QSqlTableModel* fixModel, const QModelIndex& index) const {

  Q_UNUSED(editor);
  Q_UNUSED(index);

  QPixmap fixPic;
  fixPic.loadFromData (fixModel->record (1).value ("Pic").toByteArray ());

  qDebug() << "Fixmodel pic: " << fixPic;
  qDebug() << "Fixmodel pic size: " << fixPic.size ();

}

I keep getting the following message:
QPixmap::scaled: Pixmap is a null pixmap
Wgat did I miss? Thank you for your help.

artwaw

Hi, apparently loadFromData fails.
You have hardcoded fixModel->record(1) - are you sure the data is there? In row number one?
Rows are numbered in zero-based manner.
Other problem might be that field "Pic" returns invalid value.

gabor53

Hi @artwaw ,
The data is there. There is an image in each record in the Pic field. Is it the correct way I'm trying to load the image?
Thank you.

artwaw

@gabor53 Actually in the method you posted here there should not be any hardcoded values. I would post rather elaborate answer a bit later in the evening, I am commuting now.

gabor53

@artwaw
Thank you. I would appreciate that. Also I assigned the delegate to the view like this:


  QSqlTableModel* fixModel = new QSqlTableModel(this);
  fixModel->setTable ("Items");
  fixModel->setEditStrategy (QSqlTableModel::OnFieldChange);
  fixModel->setSort (2, Qt::DescendingOrder);

  fixModel->select ();

  ui->tableView_Fix->setItemDelegateForColumn(3, new FixViewDelegate (this));

The goal would be to get the delegate draw the image each time.

SGaist

Hi,

How did you store the image data in your database ?

gabor53

Hi @SGaist ,
I store them as a QByteArray:

QPixmap pix2(fileNameChosen);
  int w = 0;
  int h = 0;
  w = ui->Image_Display_Label->width ();
  h = ui->Image_Display_Label->height ();
  ui->Image_Display_Label->setPixmap (pix2.scaled(w, h, Qt::KeepAspectRatio));

  QFile fileReview(fileNameChosen);

  if(fileReview.open (QIODevice::ReadOnly)) {
    fileByteArray = fileReview.readAll ();

jsulm

@gabor53 What @SGaist probably means is: what data type do you use for the pixmap column in the table in the database?

gabor53

Hi @jsulm ,
It's BLOB.

Vinod Kuntoji

@gabor53 ,

What is the size of the bytearray?

gabor53

@Vinod-Kuntoji
100 x 100

Vinod Kuntoji

@gabor53 ,
The blob you are using, is it a raw bytearray or png, jpeg byterray?

gabor53

@Vinod-Kuntoji
It is jpeg bytearray.

Vinod Kuntoji

@gabor53 ,

Then you should specify "JPG" in loadFromData function.

QPixmap fixPic;
fixPic.loadFromData (fixModel->record (1).value ("Pic").toByteArray (),"JPG");

gabor53

@Vinod-Kuntoji
Thank you. I've noticed an other issue: the program execution enters fixviewdelegate.cpp but never reads the actual function:

void FixViewDelegate::setModelData(QWidget* editor, QSqlTableModel* fixModel, const QModelIndex& index) const {

  Q_UNUSED(index);
  Q_UNUSED(editor);

  qDebug() << "Entered fixViewDelegate (2).";

  QPixmap fixPic;
  fixPic.loadFromData (fixModel->record (1).value ("Pic").toByteArray (), "JPG");
  qDebug() << "Fixmodel pic: " << fixPic;
  qDebug() << "Fixmodel pic size: " << fixPic.size ();

}

What can I do to fix this problem?

Vinod Kuntoji

@gabor53 said in Reading image from QSqlTableModel:

execution

What is that function?

raven-worx

@gabor53
what is output of the following code in the console:

qDebug() << QImageReader::supportedImageFormats();

Also on what system are you running your application?

gabor53

Hi @raven-worx ,

The output is

("bmp", "cur", "dds", "gif", "icns", "ico", "jpeg", "jpg", "pbm", "pgm", "png", "ppm", "svg", "svgz", "tga", "tif", "tiff", "wbmp", "webp", "xbm", "xpm").
I run Qt 5.8 on Windows 10.

raven-worx

@gabor53
ok that at least ensures you can read jpg images.
Now the only possibility is that the data you retrieve from the database isn't valid imagedata.

QByteArray ba = fixModel->record (1).value ("Pic").toByteArray ();
qDebug() << ba.size() << ba;

gabor53

@raven-worx
I added it to the

void FixViewDelegate::setModelData(QWidget* editor, QSqlTableModel* fixModel, const QModelIndex& index) const {

function but it doesnt display anything. I know program execution goes from fixdb.cpp to FixViewDelegate, but it does nothing with setModelData. As this delegate supposed to handle displaying the image without clicking on the table I think something is missing. How can I render the image using this delegate each time the tableView is displayed?
The delegate so far looks like this:

#include "fixviewdelegate.h"

FixViewDelegate::FixViewDelegate(QObject* parent) : QStyledItemDelegate(parent) {
  qDebug() << "Entered fixViewDelegate (1).";
}

void FixViewDelegate::paint(QPainter* painter, const QStyleOptionViewItem& option, const QModelIndex& index) const {

  Q_UNUSED(painter);
  Q_UNUSED(option);
  Q_UNUSED(index);
}

QSize FixViewDelegate::sizeHint(const QStyleOptionViewItem& option, const QModelIndex& index) const {

  Q_UNUSED(option);
  Q_UNUSED(index);

}

void FixViewDelegate::setEditorData(QWidget* editor, const QModelIndex& index) const {

  Q_UNUSED(editor);
  Q_UNUSED(index);

}

void FixViewDelegate::setModelData(QWidget* editor, QSqlTableModel* fixModel, const QModelIndex& index) const {

  Q_UNUSED(index);
  Q_UNUSED(editor);


  qDebug() << "Entered fixViewDelegate (2).";
  QByteArray ba = fixModel->record (1).value ("Pic").toByteArray ();
  qDebug() << ba.size() << ba;

//  qDebug() << "Fixmodel pic: " << fixPic;
//  qDebug() << "Fixmodel pic size: " << fixPic.size ();

}

Thank you for your help.