renderPixmap

[zorro68]

Two days ago this code capture perfectly the opengl screen, but now capture a black rectangle:



void Visor::BTNcaptura_click()
{
QSize size = getSize();
if (size.isValid()) {
//QPixmap pixmap = QPixmap::grabWidget(glWidget, 0,0, size.width(), size.height()); <-- this capture a green rectangle
QPixmap pixmap = glWidget->renderPixmap(size.width(), size.height()); <-- this capture a black rectangle
QString fileName = QFileDialog::getSaveFileName(this,tr("Guardar la imagen como..."),QString(),
tr("Archivos de imágenes (*.png *.jpg *.bmp *.jpeg *.ppm *.xbm *.xpm);;Todos los Archivos (*)"));
if (!fileName.isEmpty()){
QString filter=QFileInfo(fileName).suffix();
if (filter=="jpg")
pixmap.save(fileName,"jpg");
...
else
pixmap.save(fileName+".png","png");
}
}
}



What happend?

[wysota]

Did you do any modifications to your computer during the two days? Drivers update, software update...

[jpn]

Have you verified that getSize() returns what it's supposed to? What happens if you pass the image format as uppercases or even leave it out (in 4.2 it's a default parameter defaulting to 0 when the image format is guessed based on the passed filename extension).



// try
pixmap.save(fileName, "JPG"); // instead of "jpg"
// or
pixmap.save(fileName); // in this case fileName should end with ".jpg"

[wysota]

Shouldn't it be "JPEG" and not "JPG"?

[jpn]

Shouldn't it be "JPEG" and not "JPG"?
I'm not sure if it makes any difference: Reading and Writing Image Files (http://doc.trolltech.com/4.2/qpixmap.html#reading-and-writing-image-files)

[wysota]

Right, looks like it doesn't :) Although the format name is "JPEG" and not "JPG" ;)

[minimoog]

Why don't you use QGLWidget::grabFrameBuffer (http://doc.trolltech.com/4.2/qglwidget.html#grabFrameBuffer)()?

[zorro68]

wysota: This is not the problem because i have not modified my computer.
wysota and jpn: If i used upper letter dont work.
minimoog: Because I need to resize image.

I know whats the problem but I dont know how to correct it. The problem is that if i create an object at first (in this function initializeGL()) works fine, but if i create an object from a file after initializeGL() dont work.

I have read that renderPixmap run initializeGL, PaintGL and resizeGL, and thats the problem. I create an object out of this functions (reading from a file).

I wish i explain well.

[zorro68]

One question about the forum.
Green light on near the username is that the user is online?

[jacek]

One question about the forum.
Green light on near the username is that the user is online?
Yes, just like the tooltip says.

Please, next time ask such questions in more appropriate place, like Feedback section.

[minimoog]

Heh, you can use OpenGL to resize image for free (in your case just change the viewport). Or you can use render_to_texture (Framebuffer Object (http://doc.trolltech.com/4.2/qglframebufferobject.html)), or you can read directly the pixels with glReadPixels.

Anyway, if you use renderPixmap, make sure that OpenGL initialization code (like setting perspective matrices, display lists) are in InitializeGL().