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I'm trying to make video output (sequence of frames) to any qt visible widget. At beginning i thought that QLabel will be enough for this point... but i was wrong. Converting to pixmap is too overloading for processor at large images: 1080p for example.
Any other solution? (not QLabel?)
Example of code for one frame:
QImage m_outputFrameImage(width, height, QImage::Format_RGB888);
memcpy(m_outputFrameImage.bits(), m_frameRGB->data[0], height * width * 3);
QPixmap pixmap = QPixmap::fromImage(m_outputFrameImage); // BAD, slow and high load
/* Bad too (Same code?)
QPainter painter;
painter.begin(&pixmap);
painter.drawImage(0, 0, m_outputFrameImage);
painter.end();
*/
labelVideo->setPixmap(pixmap);
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A QPixmap can be used to show an image in a PyQT window. QPixmap() can load an image, as parameter it has the filename. To show the image, add the QPixmap to a QLabel. QPixmap supports all the major image formats: BMP,GIF,JPG,JPEG,PNG,PBM,PGM,PPM,XBM and XPM.
There isn't a widget specifically made for displaying images, but this can be done with the label widget. We do this with the pixmap property. QPixmap pic("/path/to/your/image"); ui->label->setPixmap(pic);
The QImage class provides a hardware-independent image representation that allows direct access to the pixel data, and can be used as a paint device.
Since you use QPixmap, you can use its copy method and supply it with a QRect to perform the actual crop. Show activity on this post. Just use of the QPixmap's copy() functions.
Yes, render the frames to a QGLWidget and let the video card handle it. That's how Qt MultimediaKit, Phonon and others do it.
Some time ago I shared some code that demonstrated how to accomplish this task: Image scaling (KeepAspectRatioByExpanding) through OpenGL
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