best way to load image from db

[C167]

Hi, i'm currently loading images from a sqlite3 blob-field using this code:
void ImageViewer::loadImage ( int pic )
{
QSqlQuery query ( QSqlDatabase::database() );
query.prepare ( "SELECT data FROM img_images WHERE id = :id" );
query.bindValue ( ":id", img_list[pic] );
query.exec();
if ( query.next() )
{
return QImage::fromData ( query.value ( 0 ).toByteArray() ) );
}
else
{
return QImage();
}
}Now i found some examples in one of my Qt-Books:
QImage ImageCollection::getImage( int id )
{
QSqlQuery qrx;
qry.prepare ( "SELECT data FROM images WHERE id = :id" );
qry.bindValue ( ":id", id );
if ( !qry.exec() ) qFatal ( "Failed to get image" );
if ( !qry.next() ) qFatal ( "Failed to get image id" );
QByteArray array = qry.value ( 0 ).toByteArray();
QBuffer buffer ( &array );
buffer.open ( QIODevice::ReadOnly );
QImageReader reader ( &buffer, "PNG" );
QImage image = reader.read();
return image;
}Which code is better, if i know that i only have one image format in the database and why? which one is the fastest?
Using Qt4.4b1, 4.4rc1 is compiling atm. System is Debian Sid.
C167

[jacek]

IMO the first version is better, because it's shorter and supports all possible images formats. It might be a bit slower, because Qt must detect the format, but I don't think you will notice the difference.

[Lykurg]

Hi,

because of QImage::fromData is defined as
QImage QImage::fromData(const uchar *data, int size, const char *format)
{
QByteArray a = QByteArray::fromRawData(reinterpret_cast<const char *>(data), size);
QBuffer b;
b.setData(a);
b.open(QIODevice::ReadOnly);
return QImageReader(&b, format).read();
}
both are equal. But as jacek mentioned your code is shorter in "front end", so I would prefer it.

If you need speed improvement store all images in the database in the same image format, and specify it in fromRawData(). Also if img_list is an private member and you definitely know the content you may use
query.exec( "SELECT data FROM img_images WHERE id = " + QString::number(img_list[pic]));
(assuming img_list[pic] will return an integer)

Lykurg