What's the fastest way to show JPG/JPEG images
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@sierdzio I will post my code here:
void MainWindow::showFrames() { QDirIterator it("/framesPath", QDirIterator::Subdirectories); it.next(); // Pass first.. it.next(); // .. two dots QString nextFirstFile = it.next(); QImage Img; Img.load(nextFirstFile); Img = Img.scaledToWidth(ui->QLabel1->width(), Qt::SmoothTransformation); ui->QLabel1->setPixmap(QPixmap::fromImage(Img)); QFile imgFile(nextFirstFile ); imgFile.remove(); }The timer in constructor:
frameTimer = new QTimer(this); connect(frameTimer, SIGNAL(timeout()), this, SLOT(showFrames())); frameTimer->start(35); frameTimer->setInterval(45);I don't know my approach is good or not, i need your help.
@sierdzio as you say:
"Lastly, if you can, try steaming the frames from your video source directly to your app."I said "I have to do it in this way. Because i'm manipulating frames with another program."
@J-Hilk
Dear J.Hilk, i've posted code how i'm trying to do. Maybe you can show me a little code example.@R_Irudezu said in What's the most efficient way to use QLabel as video player:
I said "I have to do it in this way. Because i'm manipulating frames with another program."
Yes, but perhaps that other program supports sending the data through a pipe. Or you have some influence on that program and can request streaming support to be added. Et cetera
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Also reading the additonal information you profided,
Creating a new QImage/QPixmap via QImage("filepath") is horribly expensive. Holding a Image/Pixmap in memory and changing the bytes, read via QFile; Should be a good bit faster.
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this is of course untested. And as the comment says, you have to modfy the QbyteArray to actually get the rgb(a) values you want. You'll have too look that one up. Also the memberImage needs to have the same size as the images you want to load.
void myWidget::showFrames() { QDirIterator it("/framesPath", QDir::NoDotAndDotDot, QDirIterator::Subdirectories); memberQFile.setFileName(it.next()); if(memberQFile.exists() && memberQFile.open(QIODevice::ReadOnly)){ QByteArray data = memberQFile.readAll(); //This will fail, the QByteArray has to be trimmed/changed according to img file/header memcpy(memberImage.bits(),data.data(), data.size()); memberQFile.remove();//Also automatically closes the file update();//request repaint } } void myWidget::paintEvent(QPaintEvent *event) { QWidget::paintEvent(event); QPainter p(this); p.drawImage(rect(),memberImage, memberImage.rect()); } -
There are no efficient way with QLabel.
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wrote on 19 Oct 2018, 19:22 last edited by
i've just edited the question, seperated with (____)
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Hi,
Jpeg decompression is expensive. What size are you images ? What quality ? And to what application are you going to send them ?
You might want to consider using turbo-jpeg to handle the decompression.
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Hi,
Jpeg decompression is expensive. What size are you images ? What quality ? And to what application are you going to send them ?
You might want to consider using turbo-jpeg to handle the decompression.
wrote on 19 Oct 2018, 22:26 last edited by R_Irudezu@SGaist I'm receiving jpeg data and decoding it with GDI+ in quality of between 30-50 (with a native c++ compiled .exe file)
long quality = 50; encoderParameters.Parameter[0].Value = &quality;All images save under a directory. I don't want to use any other decompress handling. Images are about 30-50 Kb and i just want to show them in a Qt item. (QLabel is very useless for this). All images will be shown with a QTimer (40 ms) and will be deleted.
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Where are you getting these images from in the first place ?
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wrote on 21 Oct 2018, 09:55 last edited by R_Irudezu
@SGaist I'm getting images from a .exe program written in C. The C program connects a camera, getting images, manipulate them with GDI+ and save them under a specific directory. The program uses some libraries, these libraries are not compatible with any of Qt versions.
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Why are they not ?
18/18