[Qt4] How to load Url image into QImage?

[Gonzalez]

Hi to all ,

I want to load an URL image , for example ,
http://mydomain.com/images/image.jpg , into a QImage.

I try some things , but no one works :



QUrl url("http://mydomain.com/images/image.jpg");
QImage image(url.toLocalFile());


or



QHttp url("http://mydomain.com/images/image.jpg");
QImage image;
image.loadFromData(url.readAll());


How to do this?

[jrideout]

I'm not too familar with qt's networking classes, but a quick scan of the docs shows that the constructor sets the host, but not the whole url. For that you need to use the get method.

See http://doc.trolltech.com/4.1/qhttp.html#get

[Gonzalez]

Done !!!.



QUrl url("http://mydomain.com/images/image.jpg");
http = new QHttp(this);
connect(http, SIGNAL(requestFinished(int, bool)),this, SLOT(Finished(int,
bool)));
buffer = new QBuffer(&bytes);
buffer->open(QIODevice::WriteOnly);
http->setHost(url.host());
Request=http->get (url.path(),buffer);

public slots:

void Finished(int requestId, bool error){
if (Request=requestId){
QImage img;
img.loadFromData(bytes);
}

private :

QBuffer *buffer;
QByteArray bytes;
QHttp *http;
int Request;

[antweb]

Hello,

I made use of your code and I am able to access Url images. The issue that i am facing is that I am not able to access all Url images. It works for some images but not for all?
Do you know what might be the issue?

Like for eg.
I am able to acquire this image : http://www.slowstop.com/images/uploads/YouTube_Logo.jpg
But not this one : http://colorlib.com/dazzling/wp-content/uploads/sites/6/2013/03/image-alignment-150x150.jpg
These are two random pics from google images.

Please help me out!

[ChrisW67]

QHttp has been deprecated for a few years now. You should rewrite your code using QNetworkRequest and related classes. There is at least one HTTP download example in the docs.

Start with a small, self-contained program that only does this one task. If your code still does not behave then please post it here and explain what the problem is.

[antweb]

I have a pretty straight forward and simple program. I have made use of QNetworkRequest this time.

.cpp code :


#include "http_new.h"
#include <QNetworkAccessManager>
#include <QUrl>
#include <QNetworkRequest>
#include <QAuthenticator>
#include <QNetworkReply>
#include <QtCore/QCoreApplication>
#include <QDebug>
#include <QImageReader>

QNetworkAccessManager* nam;

http_new::http_new(QWidget *parent, Qt::WFlags flags)
: QMainWindow(parent, flags)
{
ui.setupUi(this);

nam = new QNetworkAccessManager(this);
QObject::connect(nam, SIGNAL(finished(QNetworkReply*)),
this, SLOT(finishedSlot(QNetworkReply*)));

QUrl url("http://www.slowstop.com/images/uploads/YouTube_Logo.jpg");
QNetworkReply* reply = nam->get(QNetworkRequest(url));
}

http_new::~http_new()
{

}

void http_new::finishedSlot(QNetworkReply *reply)
{
// Reading attributes of the reply
// e.g. the HTTP status code
QVariant statusCodeV =
reply->attribute(QNetworkRequest::HttpStatusCodeAttribute );

// Or the target URL if it was a redirect:
QVariant redirectionTargetUrl =
reply->attribute(QNetworkRequest::RedirectionTargetAttrib ute);

// no error received?
if (reply->error() == QNetworkReply::NoError)
{
// read data from QNetworkReply here
QByteArray bytes = reply->readAll(); // bytes
QPixmap pixmap;
pixmap.loadFromData(bytes);
ui.label->setPixmap(pixmap);
}
// Some http error received
else
{
// handle errors here
}

// We receive ownership of the reply object
// and therefore need to handle deletion.
delete reply;
}


.h code :


#ifndef HTTP_NEW_H
#define HTTP_NEW_H

#include <QtGui/QMainWindow>
#include <QImage>
#include <QPixmap>
#include <QPainter>
#include <QColor>
#include <QNetworkAccessManager>
#include <QUrl>
#include <QBuffer>
#include <QHttp>
#include <QNetworkRequest>
#include <QNetworkReply>
#include "ui_http_new.h"

class http_new : public QMainWindow
{
Q_OBJECT

public:
http_new(QWidget *parent = 0, Qt::WFlags flags = 0);
~http_new();

public slots:
void finishedSlot(QNetworkReply* reply);

private:
Ui::http_newClass ui;
QImage * image;
QPixmap screenImage;
QPainter * p;
QBuffer *buffer;
QByteArray bytes;
QHttp *http;
int Request;
};

#endif // HTTP_NEW_H


main code:


#include "http_new.h"
#include <QtGui/QApplication>

int main(int argc, char *argv[])
{
QApplication a(argc, argv);
http_new w;
w.showMaximized();
return a.exec();
}


I am still facing the same issue as i had written earlier.
The URL i have used right now. I am able to view that image in my Label but that is not happening for every image link.
I really cannot understand why?
The second link that I have provided earlier is a working image link through browser but does not give me any image on my Label.

Please Help.

[anda_skoa]

Have you checked where the problem is?
Do you get no data or does the pixmap loading fail?

Cheers,
_