pixmap to bytearray, bytearray to pixmap

IknowQT

Use the grab() function of the chart viewer to get it as a pixmap. And save it as a bytearray in xml.
When I load the file and put it in qlabel, the message QPixmap::scaled: Pixmap is a null pixmap occurs.

QByteArray bArray;
			QBuffer buffer(&bArray);
			buffer.open(QIODevice::WriteOnly);
			this->m_pChartViewer->grab().save(&buffer, "PNG");


QPixmap fromBase64;
		fromBase64.loadFromData(src.pixByte);
this->ui.label->setPixmap(
			fromBase64.scaled(
				nw,
				nh,
				Qt::KeepAspectRatio, Qt::SmoothTransformation)
		);

Is there any way to solve it?

The loadFromData function is returning false.
I think this is the problem...

Christian Ehrlicher

How do you save and read it in to/from the xml?

IknowQT

@Christian-Ehrlicher

QS_FIELD(QByteArray, pixByte)									//	pixByte

QByteArray bArray;
			QBuffer buffer(&bArray);
			buffer.open(QIODevice::WriteOnly);
			this->m_pChartViewer->grab().save(&buffer, "PNG");

			m_pStcInfo->pixByte = bArray;

It has a bytearray as a member variable of the class.
Assign here and save the value of the member variable of this class in xml format.

===============================================================================

I have captured the contents stored in the xml file.

Christian Ehrlicher

You can/must not simply but a QByteArray in a xml - you have to encode it e.g. as base64 and decode it later on.

IknowQT

@Christian-Ehrlicher

Thank you for answer. Thanks it has been resolved.
When I save it as tobase64, the size of the file has definitely increased.
I think it was probably because of a lot of text. Is there any way to reduce the file size?

The method I tested was to save it as a QString, then convert it to tobase64() and convert it back to frombase64.

But I didn't see the results I wanted.
Is there any way to reduce the file size?

Christian Ehrlicher

@IknowQT said in pixmap to bytearray, bytearray to pixmap:

When I save it as tobase64, the size of the file has definitely increased.

I would be surprised if not - now only 64 instead 256 characters are used (only the really printable ones) - see https://en.wikipedia.org/wiki/Base64

Is there any way to reduce the file size?

Reduce the size of the picture, don't store pictures in xml.