Qt-jambi-interest Archive, December 2007
QPixmap or QImage from (Java-) InputStream
Message 1 in thread
Hello
is there any chance to read a QPixmap (or a QImage) from a Java -
InputStream (i.E. a ZipFileInputStream). I tried to copy every Byte of
the Input Stream in a QByteArray, then build a QBuffer from the
ByteArray an pass this to QImageReader, but that doesn't seem to work,
the QPixmap was empty.(and QImageReader.canRead() returns false)
I would like to create a QPixmap directly from a zipfile (in the way I
create it from a existing file = new QPixmap("file.jpg") without copy it
to the lokal filesystem.
thank you
Arne
Message 2 in thread
Arne Stocker wrote:
> Hello
>
> is there any chance to read a QPixmap (or a QImage) from a Java -
> InputStream (i.E. a ZipFileInputStream). I tried to copy every Byte of
> the Input Stream in a QByteArray, then build a QBuffer from the
> ByteArray an pass this to QImageReader, but that doesn't seem to work,
> the QPixmap was empty.(and QImageReader.canRead() returns false)
>
> I would like to create a QPixmap directly from a zipfile (in the way I
> create it from a existing file = new QPixmap("file.jpg") without copy it
> to the lokal filesystem.
Hi Arne,
I don't know why your approach wouldn't work. Maybe you didn't have the
jpeg plugin in the QT_PLUGIN_PATH? Anyway, below is an example of how
you can use QPixmap.loadFromData() to achieve this quickly.
import com.trolltech.qt.core.*;
import com.trolltech.qt.gui.*;
public class ImageFromBytes
{
public static void main(String args[]) {
QApplication.initialize(args);
QFile f = new QFile("image.png");
if (!f.open(QFile.OpenModeFlag.ReadOnly)) {
System.out.println("failed to open image.png...");
return;
}
QByteArray data = f.readAll();
QPixmap pixmap = new QPixmap();
if (!pixmap.loadFromData(data, "PNG")) {
System.out.println("failed to load image data...");
return;
}
QLabel label = new QLabel();
label.setPixmap(pixmap);
label.show();
QApplication.exec();
}
}
Another way of doing this would be to use our resource system. Say that
you have 50 icons in your app, like close.png, fileopen.png, etc. If you
put these into a .jar file and put the .jar file into the CLASSPATH you
would be able to do:
QPixmap closeIcon = new QPixmap("classpath:path_in_jar_to/close.png");
and it would just load it automatically.
best regards,
Gunnar
Message 3 in thread
> I don't know why your approach wouldn't work. Maybe you didn't have the jpeg plugin in the QT_PLUGIN_PATH? Anyway, b
Hello Gunnar
sorry it was my fault, but there is no problem to load a QPixmap from an
existing file (that works well). The problem is that I have a zipped
file wich includes several pictures (i.e. jpg's).
In Java I could open an InputStream for everey file in the zip-archiv
withoud extract the whole zipfile to the disk. In return I get an (Java)
InputStream from wich I could read the data (as I do with the included
metainfo file in xml-format).
Now I want to create a QPixmap direktly from that (Java) InputStream
(the Object is from the type ZipFileInputStream). So all I need is to
read the Bytes from the InputStream to the QByteArray.
I did it byte for byte (which needs a lot of time), then create an Image
in that way
int read = 1;
QByteArray bytearray = new QByteArray();
while (read >= 0) {
read = inputstream.read(); // read() returns 0-255 or -1
if (read >= 0) {
bytearray.add((byte) inputstream);
}
}
QBuffer buffer = new QBuffer(bytearray);
QImageReader ireader = new QImageReader(buffer,new QByteArray("jpg"));
if (imagereader.canRead() {
return imagereader.read();
}
this way failed.
I will try it with the QPixmap.LoadFromData() again.
By the way : is there a better (faster) way to read a (Java) InputStream
in a QByteArray except copy it byte for byte ? It would be nice if
QByteArray has an Interface to the (Java) InputStream.
best regards Arne
